Dissertations / Theses on the topic 'Food yeast'
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Minabe, Masaharu. "The lipids of post-fermentation yeast." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/1487.
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Gopal, Chandra V. "Expressed recombinant genes and yeast energy metabolism." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314759.
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Tudor, E. A. "Yeast contamination of meats and processing equipment." Thesis, University of Bath, 1989. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234640.
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Oro, Lucia. "Role of yeast bioactive compounds in food and fermented beverages." Doctoral thesis, Università Politecnica delle Marche, 2014. http://hdl.handle.net/11566/242761.
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Negli ultimi anni le molecole bioattive con attività antimicrobica come tossine killer,
batteriocine e agenti antifungini sono state impiegate per ridurre o inibire la crescita e
lo sviluppo di funghi, lieviti e batteri indesiderati in alternativa o in combinazione
con i composti sintetici antimicrobici negli alimenti e nelle bevande fermentate. La
presente ricerca riguarda il ruolo e la caratterizzazione di molecole bioattive prodotte
da lieviti appartenenti alle specie Metschnikowia pulcherrima, Tetrapisispora phaffii,
Kluyveromyces wickerhamii, Wickerhamomyces anomalus. Dopo la caratterizzazione
dei composti bioattivi prodotti da questi lieviti e lo studio dell'interazione tra le
molecole antimicrobiche naturali e i lieviti/ le muffe sensibili, abbiamo voluto
valutare il loro possibile impiego per combattere microrganismi contaminanti
nell’agricoltura biologica e nel settore vinicolo.
Nella prima parte della tesi è stata valutata l’azione inibente di sette ceppi di M.
pulcherrima nei confronti di lieviti enologici principalmente coinvolti nel processo di
vinificazione come Pichia, Candida, Hanseniaspora, Kluyveromyces,
Saccharomycodes, Torulaspora, Brettanomyces e Saccharomyces. Un’efficace
azione antagonista dei ceppi di M. pulcherrima è stata osservata nei confronti di
lieviti indesiderati appartenenti ai generi Pichia, Brettanomyces e Hanseniaspora,
mentre tale attività antimicrobica non si evidenziava nei confronti di Saccharomyces
cerevisiae.
Il secondo argomento trattato ha riguardato l’isolamento del gene che codifica Kpkt,
la tossina killer prodotta da Tetrapisispora phaffii che possiede un’ampia attività
antimicrobica nei confronti di vari lieviti alterativi del vino. La distruzione del gene
ha provocato una perdita completa del fenotipo killer confermando così che TpBgl2p
esercita un'attività antimicrobica. Il risultato ottenuto è la base per valutare la
possibilità di esplorare la produzione eterologa della proteina che potrebbe essere
utilizzata in campo enologico per ridurre le contaminazioni nel vino in sostituzione
della SO2.
Nella terza parte della tesi, l’attenzione è stata focalizzata sul danno indotto dalle
tossine Kwkt and Pikt, prodotte rispettivamente da Kluyveromyces wickerhamii e
Wickerhamomyces anomalus, coinvolte nel biocontrollo dei lieviti spoilage
Brettanomyces/ Dekkera in vinificazione. L’effetto delle micocine è stato comparato
con quello dell’anidride solforosa, generalmente usata come composto sintetico
antimicrobico negli alimenti e nelle bevande fermentate. I risultati hanno mostrato
diversi meccanismi di controllo della crescita di B. bruxellensis tra le due tossine e
tra le tossine killer e il biossido di zolfo, anche se l'attività antimicrobica di
quest’ultimo è fortemente influenzata dal fattore pH.
Nella quarta parte della tesi è stata valutata l'interazione tra diversi lieviti ad attività
antimicrobica e alcuni funghi filamentosi che in genere colonizzano i frutti maturi.
Preliminarmente è stato eseguito uno screening in piastra per valutare l’eventuale
effetto inibente di 42 lieviti verso 5 muffe, che causano i principali danni in frutta e
verdura durante il periodo di post-raccolta. In una seconda fase, dieci ceppi
selezionati sono stati testati per la loro attività inibitoria efficace contro le muffe in
test in vivo su uva, limoni, arance, fragole e ciliegie. I risultati indicano che, tra i
ceppi saggiati la migliore e interessante attività antagonista nei confronti delle muffe
testate, è stata mostrata da due ceppi appartenenti a Wickerhamomyces anomalus e
Metschnikowia pulcherrima.In recent years, the bioactive compounds with antimicrobial activity such as yeast killer toxins, bacteriocins and natural antifungal agents are employed to reduce or inhibit the growth and the development of undesired fungi, yeasts or bacteria. Their use was proposed in alternative or in combination to the addition of synthetic antimicrobial agent in food and fermented beverage. The present research focused on the antimicrobial role and the characterization of bioactive molecules produced by yeast strains belonging to Metschnikowia pulcherrima, Tetrapisispora phaffii, Kluyveromyces wickerhamii, Wickerhamomyces anomalus species. Following a characterization of the antimicrobial compounds produced by these yeasts and investigating on the interaction between natural antimicrobial molecules and sensitive yeasts/moulds, the present study focused the attention on their use to combat contaminating microorganisms in “organic” agriculture and in wine industry. In the first part of the present thesis seven different strains of M. pulcherrima were screened to evaluate the growth inhibition of the main oenological yeasts such as Pichia, Candida, Hanseniaspora, Kluyveromyces, Saccharomycodes, Torulaspora, Brettanomyces and Saccharomyces involved in winemaking process. The effective antagonistic actions of M. pulcherrima strains was showed on undesired wild spoilage yeasts, such as the Pichia, Brettanomyces and Hanseniaspora genera, while Saccharomyces cerevisiae was not affected by the antimicrobial action of M. pulcherrima. The objective of the second part of this study was the isolation of the gene encoding Kpkt, a killer toxin produced by Tetrapisispora phaffii. The gene disruption caused a complete loss of the killer phenotype thus confirming that TpBgl2p exerts an effective killer activity and that the gene is effectively involved in the expression of the zymocin. The result obtained gives the basis to explore the heterologous production of the protein that could be used as starter in enological field to reduce wine contamination. In the third part of the thesis, the attention was focused on the damage induced by Kwkt and Pikt killer proteins, produced by Kluyveromyces wickerhamii and Wickerhamomyces anomalus, involved in the biocontrol of Brettanomyces/ Dekkera spoilage yeast in the wine industry. The effect of mycocins was also compared with sulfur dioxide, generally used as antiseptic in food and beverage industries. The results showed different mechanisms of control of B. bruxellensis growth within the two mycocins. Different mechanisms of action were also found between killer toxins and sulfur dioxide that is strongly influenced by pH. In the fourth part of this work it was evaluated the interaction between several yeasts that exhibit antimicrobial activity and some filamentous fungi that generally colonize mature fruits. Preliminarily, a plate screening was performed to assess inhibitory effect of 42 yeasts against 5 moulds, main spoilage microorganisms in vegetables and fruits during postharvest. In a second step, ten selected strains were tested for their effective inhibitory activity against moulds in vivo assay on grapes, lemons, oranges, strawberries and cherries. Results indicated that the best antagonistic activity was exhibited by Wickerhamomyces anomalus and Metschnikowia pulcherrima species that produced a significant reduction of moulds.
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Pires, Xavier Alexandre Cabaceira. "Implementação do referencial IFS (International Food Standard) numa indústria de produção de leveduras para panificação e pastelaria." Master's thesis, ISA/UTL, 2011. http://hdl.handle.net/10400.5/4124.
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Mestrado em Engenharia Alimentar - Qualidade e Segurança Alimentar - Instituto Superior de AgronomiaThe growing concern over food safety companies with international presence and the requirements of many European retailers and wholesalers increase the need for integration with other standard quality management systems. The work consists in study the implementation of standard IFS in an industry that produces yeast for baking and pastry, Lallemand Ibéria, SA. In a preliminary step, it was obtained the International Food Standard version 5 - which includes guides, guidelines and requirements for the certification process. The standard has been studied and analyzed in order to understand the best methods to meet the requirements, and was researched the applicable legislation to food and the published literature. It was made a pre-audit to evaluate the current situation of the company. Then it was found and worked out all the associated documentation, as well as an action plan and changes to be considered for the implementation of the standard. In this context has been revised the quality and food safety systems implemented and were made significant changes in the company to adapt to the requirements of this standard.
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Richelle, Anne. "Modelling, optimization and control of yeast fermentation processes in food industry." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209280.
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A macroscopic model describing the main physiological phenomena observed during the fed-batch baker’s yeast production process and including the influence of nitrogen on the key bio-mechanisms is proposed. First, on the basis of a set of biological reactions, inspired by the model of Sonnleitner and Käppeli, a model in which the nitrogen and glucose consumption are coordinated is proposed. Second, an attempt of estimating storage carbohydrate contents in yeast cells through an extension of this model is presented. The model is identified and validated with experimental data of fed-batch yeast cultures and successfully predicts the dynamics of cell growth, substrate consumption (nitrogen and carbon sources) and metabolite production (ethanol and storage carbohydrates). The developed model was used for the determination of optimal operating conditions, in the sense of a production criterion. To this end, two different approaches were used: a control vector parameterization approach and a semi-analytical formulation of the optimal operating policy. The two approaches were compared with numerical and experimental data. The results of the two approaches lead to the determination of similar optimal operation conditions, which have been implemented for a new experimental phase. Moreover, these optimal conditions are in agreement with the profiles obtained by industrial manufacturers through an empirical optimization of the process.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Faulkner, James Duncan Bruce. "A novel series of expression vectors for use in the yeast Saccharomyces cerevisiae." Thesis, University of Kent, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334250.
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Miura, Yutaka. "Studies on the high-level production of various food-related materials in the food yeast Candida utilis." Kyoto University, 2000. http://hdl.handle.net/2433/181073.
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Matni, Gisèle. "Speciation of selenium in food supplements." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40393.
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Selective isolation protocols of selenium (Se) species integrated to Se specific atomic absorption spectroscopy (AAS) detection were developed and optimized for Se speciation in food supplements, including selenized yeasts. By ultrafiltration, 69.18% of Se in the extract was found as a low molecular weight soluble form, the remaining 30.82% was bound to high molecular weight components. After a cation-exchange chromatography of the ultrafiltrate, 3.77% of the Se in the extract was found in the aqueous washings of the column indicating the presence of free inorganic anions of Se; the 65.41% of Se retained on the column corresponded to the free organic Se cations. The limit of detection for the HPLC-THG-AAS system was 1.85 ng of Se. Se was shown to be widely distributed over all the proteins with one sharp peak corresponding to the free forms of Se. Four major peaks were found at MW $>$ 250 000 Da (15.97% of Se recovered), between 102 330 and 117 490 Da (7.06%), between 48 977 and 53 703 Da (12.71%) and close to the dye migration band (17.25%).Selective isolation and HPLC-AAS protocols were also developed and optimized for the determination of free organic forms e.g. selenomethionine (SeMet), selenocystine (SeCystine) and inorganic forms of selenium in aqueous solutions, and in complex matrices such as nutritional supplements and mixtures of free amino acids. The selenoamino acid in alkaline solution was first derivatized with 1-fluoro-2,4-dinitrobenzene. After removal of excess of reagent by partitioning with diethyl ether, the N-dinitrophenyl (DNP)-derivatized selenoamino acid was acidified and extracted with diethyl ether. Inorganic Se(IV) was extracted from the acidic aqueous phases by complexation with 1,2-phenylenediamine, forming a piazselenol. Se derivatives were determined selectively by HPLC-THG-AAS. A selective chromatographic mechanism based on $ pi$-electron interactions was optimized using a silica stationary phase derivatized with p-nitrophenyl moieties. Co-injections of DNP-SeMet, DNP-SeCystine and piazselenol save retention times of 3.7, 4.0 and 4.9 min, respectively, using a methanolic mobile phase containing 1.5% triethylamine and 0.013M acetic acid. Primary analytical validation parameters including stability, linearity and limits of detection were obtained using purified DNP-SeMet, DNP-SeCystine and piazselenol standards which were characterized by $ sp1$H-, $ sp{13}$C- and $ sp{77}$Se-NMR analysis and/or fast atom bombardment MS techniques. The calibration graphs for sequential dilutions of these Se standards were linear and the limits of detection from the resultant calibration graphs were 17 ng, 0.21 ng and 18.53 ng of Se, respectively. The purified DNP-SeMet and DNP-SeCystine were found to be photosensitive. The recovery of SeMet, SeCystine and inorganic Se from the stock solutions and/or nutritional supplements was virtually quantitative. In the presence of a 500-fold excess of other amino acids, the recovery of SeMet and SeCystine (96.1 $ pm$ 3.9% and 98.08 $ pm$ 4.2%, respec
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Jenkins, David Martyn. "The impact of dehydration and rehydration on brewing yeast." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/29243/.
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In the brewing industry it is standard practice to propagate a pure yeast culture and inoculate (pitch) it into the fermentation vessel. Once fermentation is complete, yeast is recovered and reused in subsequent fermentations (known as serial repitching) until a decline in performance occurs or the required number of successive fermentations has been conducted. Propagation is currently required to initiate the entire process again, which requires additional equipment, energy, water inputs and time. It has long been proposed that Active Dried Yeast (ADY) offers an alternative method of yeast supply. Adoption of this innovation by the brewing industry has been low because of perceived issues with the fermentation performance of ADY, the availability of strains and hygiene concerns. In the current study the fermentation performance of ADY has been assessed with respect to viability, genomic stability, membrane integrity, yeast growth, attenuation, uptake of wort nutrients and aspects of flavour development. ADY requires rehydration before use and it has been demonstrated that viability is impaired in these slurries, though the extent of viability loss was dependent on strain and rehydration conditions. The source of cell death is unclear. Mitochondrial and genomic DNA integrity was assessed using a variety of techniques and shown to be unaffected by dehydration and rehydration. In contrast membrane integrity was affected. Changes in membrane fluidity, sterol content and fitness to perform could be detected in ADY. Performance of ADY in fermentation was also impaired. A lag in cell growth, attenuation and sugar and amino acid uptake were noted. Diacetyl formation occurred more rapidly and end fermentation diacetyl levels were higher for ADY. These differences were not maintained during serial repitching. It is proposed that ADY could be utilised to replace freshly propagated yeast, but direct addition to fermenters would require an improvement of performance during the first fermentation.
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Ngongang, Maxwell Mewa. "Production of biopreservation compounds from non-Saccharomyces yeast using a single-stage bioreactor." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2372.
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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.Microbial spoilage has been reported in various food products and this has led to increased food, fruit and beverage losses, thereby threatening economic growth, food safety and security. Furthermore, statistics have shown that more than 30% of agricultural produce in developing countries, mostly in Africa, is lost owing to microbial spoilage. Beverages, food and fruits are predominant contributors to the South African export market. In recent years, contamination of these products resulting in spoilage has been a problem, although partial spoilage control has been achieved using chemical preservatives such as dimethyl dicarbonate, sodium benzoate, potassium sorbate, and sulphur dioxide (SO2). However, prolonged exposure to these chemical preservatives can cause human health problems such as skin and/or eyesight damage, muscle and stomach pain, cardiovascular disease and the impairment of brain function. To mitigate such health concerns, biologically benign alternatives are deemed suitable, providing the rationale for this study.
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Holyoak, Caroline Dawn. "Mechanisms of weak acid adaptation in Saccharomyces cerevisiae." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324945.
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McGuire, Lynne. "Determination of the molecular and physiological basis of citric acid tolerance in spoilage yeast /." St Andrews, 2009. http://hdl.handle.net/10023/738.
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Obinna-Echem, Patience Chisa. "Development of a Nigerian fermented maize food 'Akamu' as a functional food." Thesis, University of Plymouth, 2014. http://hdl.handle.net/10026.1/2983.
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Akamu is a lactic acid bacteria fermented cereal-based food that complements infant diets in most African countries. Uncontrolled fermentation increases the variability in quality and safety of akamu. This study was aimed at the controlled fermentation of akamu with selected lactic acid bacteria (LAB), investigation of the probiotic potential of the LAB and the effect of variation in production method on the product quality and sensory properties. PCR-DGGE analysis of traditional akamu samples revealed LAB community dominated by Lactobacillus fermentum, L. plantarum, L. delbrueckii subsp. bulgaricus and L. helveticus. Isolated yeasts were Candida tropicalis, C. albicans, Clavispora lusitaniae and Saccharomyces paradoxus. The isolated Lactobacillus plantarum strains (NGL5 and NGL7) fermented irradiated ground maize slurries and produced significant levels of lactic acid (>73 mmol L-1) and low pH ≤3.63 displaying inhibitory activity against Salmonella enterica serovar Enteritidis NCTC 5188, Escherichia coli 1077 (NCTC 11560), Bacillus cereus NCIMB 11925, Staphylococcus aureus NCTC 3750 and Listeria monocytogenes NCTC 7973 in MRS agar and E. coli 1077 in maize slurry fermentation. Viability of both strains of L. plantarum at pH 2 after 3 h was reduced from ≥8.26±0.05 to ≤4.94±0.49 Log10 CFU mL-1 while incubation in 0.3% bile allowed growth to 5.73±0.13 and 7.93±0.12 Log10 CFU mL-1 after 6 h for NGL5 and NGL7 respectively. Auto-aggregation of the L. plantarum strains at 37oC (≥25 after 5 h) correlated with adhesion to hydrocarbons (<15, 26, 33 and 64% for Hexane, Hexadecane, Ethyl acetate and Chloroform respectively). The strains failed to exhibit gelatinase or haemolytic activity but adhered to porcine mucin (OD403 nm ≥0.63 with viability ≥6.52 Log10 CFU mL-1) and Caco-2 cells (≥5.13 Log10 CFU mL-1). The ash, mineral (Ca, K, Mg, Na, S and Zn), IDF, SDFP and TDF content of the L. plantarum fermented ground maize slurries were significantly (p≤0.05) higher than that of the traditional akamu but the peak and final viscosities (139.5 and 68.5 cP respectively) were significantly (p≤0.05) the least. The aroma, appearance, colour, flavour and texture of the resultant porridges were liked moderately by 75% of the assessors. This study demonstrated that fermentation with the L. plantarum strains would contribute towards product safety and the L. plantarum strains possessed some probiotic potential that could be beneficial to the consumers particularly in those developing countries were the main staple foods are fermented cereals.
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Somani, Abhishek. "The responses of lager brewing yeast to low temperatures." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/28783/.
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The removal of yeast biomass (cropping) at the end of fermentation to inoculate a subsequent fermentation (serial-repitching) is common practice in the brewing industry. Between successive fermentations cropped yeast is stored as a slurry in cooled storage vessels under anaerobic conditions until required for subsequent use. Maintenance of yeast quality during storage is critical for subsequent fermentation performance. An assumption is made in brewing that all strains benefit from storage at 3-4°C. To test this assumption a model working system was initially established to assess cooling times of lager yeast in different suspension media. Preliminary investigations focussing on freshly propagated yeast slurry demonstrated that whilst the deleterious effects of extremely high storage temperatures on lager brewing yeast physiology was in line with expectation, utilization of traditionally recommended storage temperatures does not necessarily benefit yeast physiology when compared to slurry maintenance at slightly higher temperatures. Genome-scale transcriptional analysis in slurries cropped following an initial fermentation suggested that lager yeast might experience cold stress during slurry maintenance at typically recommended storage temperatures. In contrast, maintenance of lager yeast at a slightly higher storage temperature, in this case 10°C, yielded no adverse impact on key indicators of brewing yeast physiological state or on subsequent fermentation profiles following repitching into fermentations. Whilst these observations were not made using full production scale, they do indicate that optimal storage may not be currently being deployed for brewing yeast at full scale.
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Watanabe, Yukio. "Molecular breeding of yeast Saccharomyces cerevisiae for effective ammonia production from food processing wastes." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263698.
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Bryant, Nichole Elizabeth. "The Effect of Alcohol and Bitterness Levels on Brewing Yeast Viability." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/1995.
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Two of the most popular beer styles within the craft brewing industry are India Pale Ales (IPA’s) and those with high alcohol by volume (ABV). Production of these styles requires high gravity fermentation and high amounts of bittering hops in order to reach the required values for ABV and International Bitterness units (IBU) respectively. The aim of this study was to determine the impact of high gravity fermentation and high IBU levels on yeast viability and repitching cycles.
An initial experiment on high gravity fermentations was done in order to assess the effects this variable had alone. Successive five day fermentations employing serial re-pitching were performed on worts with low (10 °P), medium (14 °P), and high (18 °P) gravity levels. The minimum viability for repitching established for this study was 85%. Once the viability of a sample fell below this minimum, it would not be suitable for repitching. It was found that increasing gravity level led to lower viabilities at the end of the fermentation period. Viability decreased further as fermentation generation increased for the high gravity samples. Yeast harvested from low gravity fermentations could be repitched up to eight times. Medium and high gravity fermentations could be repitched up to five times.
This study was repeated at single gravity levels with low (25), medium (50) and high (75) IBU levels. A loss in viability with increased IBU levels over serial re-pitching cycles in the low gravity wort (10 ºP) was observed. It was found that at the low gravity level, yeast could be repitched eight times at the low IBU level, five times at the medium IBU level, and four times at the high IBU level.
When the experiment was repeated with medium and high gravity worts, the results indicated that the compound effects of increased gravity and IBU levels significantly reduced yeast viability throughout re-pitching cycles and thus limits the number of times that this yeast could be reused when compared to low gravity and low IBU fermentations. Medium gravity fermentations could be repitched three times at the low IBU level and twice at the medium and high IBU levels. High gravity fermentations could be repitched three times at all IBU levels.
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Shelton-Smith, John. "The role of anaerobic digestion in the sustainable treatment of yeast related food industry waste." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/10555.
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The worldwide yeast extract business is large and may increase with the interest in natural products and nutrients. The wastes from the yeast extract industry have traditionally been used as animal food or soil injection for agricultural benefit. This process is now being challenged and is experiencing increasing costs therefore alternative options for disposal routes are being considered. The poor biodegradability of activated sludge cell walls is well known and it has been suggested that the rigid, double layered yeast cells will be even more recalcitrant. Previous work reviewed in the thesis, had indicated yeast cell walls are some of the most refractory natural microbes in comparison, for example with activated sludge. The thesis revisits the issue of solids hydrolysis and in particular with a waste containing yeast cell walls as model solids. The literature review discusses previous work on the treatment of yeast containing wastes, including reactor designs and potential pre-treatments. It covers the work done on the fundamental characteristics of solids which might affect biodegradation rates, e.g. particle size, cross linking, rigidity and viscosity. Laboratory experiments were conducted and the results analysed from batch biodegradability testing and continuous simulation trials comparing anaerobic reactors. These were CSTR, Filters and UASB the latter noted for its vulnerability to solids. Laboratory work is also reported on the potential for ultrasonic, thermal and acclimatization to improve degradation rates. Utilisation of ultrasonic pre-treatment at 20,000 KHz, increased soluble organic carbon from between 14 to 120% dependant upon power and exposure time period. The results also showed that continuous recycle at low power produced the best results with increased gas yield and organic conversion from a lower solids retention. Results are also reported from onsite pilot trials using a 25m3 UAF digester and an analysis of previously unreported full scale yeast processing plants in the UK. These results confirmed that solids (cell) degradation rates were low. In conclusion the thesis suggests the degradability of the yeast cells are linked to their unique cell walls. Anaerobic digestion does give organic conversion albeit with long HRT's. The use of ultrasonics as a pre-treatment process enhances this conversion and improves gas yield.
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Zhuang, S. "The relationship between high gravity brewing, key performance indicators and yeast osmotic stress response." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/27767/.
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High Gravity (HG) and Very High Gravity (VHG) fermentations are increasingly attractive within the brewing industry as a means of energy-saving and to optimise process efficiency. However, the use of highly concentrated worts is concomitant with a number of biological stress factors and in particular elevated osmotic pressure, which can impact on yeast quality and fermentation performance. In order to eliminate or reduce such negative effects, yeast cells often respond to their environment by adapting their central carbon metabolism and by making osmotic adjustments. The aim of this research was to investigate the impact of wort gravity on carbon flux, key performance indicators and to examine the effect of external osmolality (as a measure of osmotic pressure) on cell physiology. The fermentation performance of lager and ale brewing yeasts in standard (13 °P), HG (18 °P) and VHG (24 °P) worts was assessed with respect to the uptake of wort sugars, and the production of key carbon metabolites. Estimation of carbon partitioning revealed that products including trehalose, glycogen, higher alcohols and esters had only minor effects on carbon distribution, whereas the production of yeast biomass acted as a major trade-off with ethanol production. Moreover, parallel analysis of the fermentation environment indicated that osmolality increased during fermentations, particularly at high gravities, with the largest contribution directly related to ethanol production. Consequently, yeast cells were subjected to a series of increasing osmolality levels induced by sorbitol, designed to replicate high gravity conditions. These conditions were shown to have a negative impact on yeast viability and vitality, although cell genome integrity was unaffected. In addition, cells responded to osmotic pressure by modifying membrane components leading to a change in fluidity, and by promoting glycerol production. It is anticipated that the data presented here will provide a greater understanding of the response of yeast to HG and VHG conditions, potentially leading to process optimisation in the future.
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Mollapour, Mehdi. "Molecular genetic analysis of preservative resistance in Zygosaccharomyces bailii." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369230.
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Parafati, Lucia. "Biological control of postharvest phytopathogenic molds promoted by food-isolated yeasts." Doctoral thesis, Università di Catania, 2016. http://hdl.handle.net/10761/3993.
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The mechanisms of action of antagonistic food-isolated yeasts, Wickerhamomyces anomalus, Metschnikowia pulcherrima, Aureobasidium pullulans and Saccharomyces cerevisiae, were evaluated. For each yeast species, different mechanisms involved in biocontrol activity against pathogenic molds, such as iron competition, production of cell wall-degrading enzymes, production of VOCs (Volatile Organic Compounds), and biofilm formation were clarified.
The second objective was to determine the efficacy of yeast strains in controlling gray mold caused by Botrytis cinerea on table grapes and strawberries, and green and blue mold decays caused by Penicillium digitatum and Penicillium italicum, respectively, on mandarin fruits. Therefore, subsequent studies investigated the potential use of locust bean gum (LBG) edible coating enriched with antagonistic yeast cells and of a commercial carrier (polyacrylammide hydrogel spheres) emitting antifungal VOCs produced by yeasts.
Among tested yeast strains, W. anomalus BS91 showed great antagonistic activity both by direct application of yeast cells and by application of VOCs. This strain is known to produce killer toxins that have been demonstrated to be exoglucanases, coded by the genes WaEXG1 and WaEXG2. To better understand the involvement of these genes in the antagonist activity of W. anomalus, characterization of the gene expression level of EXG1 and EXG2 in different yeast-host-pathogen interactions was carried out.
The present study demonstrated the efficacy of the selected yeasts as postharvest antifungal agents both by direct application and incorporation in an edible coating (LBG). Moreover, it has been demonstrated as production of VOCs can play an essential role in the antagonistic activity of BCAs, suggesting a future use of polyacrylammide hydrogel beads as VOCs emitters during the shelf-life.
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Mott, Alexander Charles. "The relationship between very high gravity fermentations and oxidative stress in the lager yeast Saccharomyces pastorianus." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/40232/.
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Very High Gravity fermentations are an increasingly attractive proposition within the brewing industry as a means of energy saving and optimising process efficiency. However, the use of very high gravity ( > 20°P) wort is associated with a range of biological stress factors. Ethanoic and osmotic stresses have been widely analysed along with oxidative stress in relation to propagation and early stage fermentation. The aim of this research was to investigate the impact of wort gravity on oxidative stress, and understand how this affects the plasma membrane at VHG. Finally the effect altered ergosterol content was analysed. The characteristics of Saccharomyces pastorianus strains were assessed for their ability to withstand the increased pressures of VHG (22°P) fermentations. VHG fermentations showed increase ethanol production at the expense of fermentation length, and increased ethanol production during VHG fermentations was offset by an increase in fermentation length. All fermentations were observed to accumulate ROS and increased antioxidant levels, with levels being furtherelevated in the VHG environment. Further analysis of S. pastorianus strains indicated that the levels of oxidative stress observed in fermentation had a negative effect on membrane fluidity and increased damage of the plasma membrane was observed. Analysis of ergosterol enriched yeast indicated that although fermentation rate was increased, a trade off with alcohol and biomass production was observed. Furthermore in response to oxidative stress, ergosterol enriched yeast showed reduced tolerance, decreased membrane fluidity and increased membrane damage. This work will give further insight into the response of lager yeast to oxidative stress present during VHG fermentations.
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Choi, Wai Ming. "Culturing grass carp and grey mullet using food waste incorporated with traditional Chinese medicine, Baker's yeast and enzymes." HKBU Institutional Repository, 2013. https://repository.hkbu.edu.hk/etd_oa/12.
Full textAbstract:
The present study focused on using food wastes and feed supplements, e.g. enzymes (bromelain and papain), baker’s yeast and Traditional Chinese Medicines (TCMs) for rearing freshwater fish (grass carp and grey mullet) in Hong Kong. Different types of food wastes, e.g. meats, bones, cereals, fruits and vegetables were collected from local hotels, mixed in different ratios and processed into feed pellets for feeding trials. The cereal dominant food waste feed (FW A) was more suitable for grass carp and grey mullet, with the best growth performance (e.g. feed conversion ratio (FCR), specific growth rate (SGR)) and higher protein digestibility (in grass carp), compared to FW B and FW C which contained higher proportions of meat products. The NBT (Nitroblue Tetrazolium) activities in blood and plasma protein levels were decreased in the grass carp, cultured with food waste feeds without any supplements, compared to the commercial feed, Jinfeng®, 613 formulation (Control). Upgrading FW A by the addition of 1% and 2% mixtures of bromelain and papain significantly increased the feed protein solubility and subsequent to growth (SGR and relative weight gain (RWG)) and feed utilization (e.g. apparent net protein utilization (ANPU), protein efficiency ratio (PER)) in both fish species. The protein and feed utilizations by grass carp were also promoted by the yeast supplements with the optimal dose of 2.5% yeast (S. cerevisiae) added to FW A upgraded by enzymes. This showed that yeast could further enhance nutrient utilization contained in feeds after addition of bromelain and papain. The in vitro study on the grass carp’s plasma treated with TCM extracts also showed that TCM extracts could stimulate plasma bactericidal activity (on Aeromonas hydrophila), possibly through enhancing plasma complement activity. The formulation with Radix scutellaria, Rhizoma coptidis, Herba andrographis and Radix sophorae flavescentis in the ratio of 1:1:2:3 was more effective in enhancing plasma bactericidal activity than single TCM extracts. Besides, R. coptidis and R. scutellaria possessed the strongest antimicrobial activity (in vitro) on fish pathogens (such as A. hydrophila, Lactococcus garvieae and Vibrio cholerae) among the 17 tested TCMs. In addition, TCMs were less likely for developing drug resistant pathogens than antibiotics. Grass carp immunity (NBT activity in blood, plasma bactericidal activity and total immunoglobulin level) was boosted by the addition of TCM formulation and baker’s yeast (S. cerevisiae). The disease resistance to pathogen (A. hydrophila) was also enhanced, with significantly lower mortalities observed in groups feeding with TCM (1 and 2% for 21 to 28 days) and baker’s yeast (2.5 and 5% for 28-56 days). The uses of yeast and TCMs led to positive effects on growth, immunity and disease resistance to pathogens in fish, but the effects (grass carp) were less effectual when both were supplemented in feed. The combined use of both supplements may impair the effects of TCM formulation or yeast in the modulation of gut mircoflora, and upset the balance of beneficial microbial communities. The present study demonstrated the feasibility of using feed supplements (TCM and baker’s yeast) to enhance fish immunity and enzymes upgraded food waste feeds for rearing fish, for the development of a more sustainable aquaculture in Hong Kong.
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SABBATINI, RICCARDO. "A study of pro-technological and spoilage yeasts in the food industry." Doctoral thesis, Università Politecnica delle Marche, 2020. http://hdl.handle.net/11566/274624.
Full textAbstract:
I lieviti hanno un impatto significativo sugli alimenti, migliorando le loro proprietà organolettiche e promuovendo benefici sulla salute. D’altro canto, essi sono un importante causa di deterioramento degli alimenti ed è necessario incrementare le conoscenze sui lieviti alterativi attraverso lo studio e lo sviluppo di tecniche volte a rilevare e quantificare questi microorganismi in un modo rapido e veloce. Inoltre, è importante lo sviluppo di strategie, come l’utilizzo di conservanti naturali, atte ad ostacolare la crescita di tali lieviti. Lo scopo di questa tesi di Dottorato di Ricerca è lo studio dei lieviti sotto due punti di vista: i) lieviti con un ruolo pro-tecnologico nell’industria alimentare e ii) lieviti con un effetto dannoso sugli alimenti. All’interno del primo argomento, è stato condotto uno studio sul ruolo attivo di Saccharomyces cerevisiae e del luppolo nella produzione di nicotinamide riboside, una forma di vitamina B3, nelle birre artigianali. Questo studio potrebbe essere il primo passo per produrre una birra a basso contenuto alcolico, con un alto contenuto di vitamina B3. Inoltre, è stata effettuata una caratterizzazione microbica dei grani di kefir provenienti dalla Bosnia ed Erzegovina e sul loro utilizzo per la produzione di kefir nei metodi tradizionale e backslopping. I grani di kefir consistono in un consorzio simbiotico di batteri lattici, lieviti e batteri acetici, incorporati in una matrice di polisaccaridi. È stata valutata anche la diversità delle dinamiche microbiche, dei profili nutrizionali e dei volatilomi del kefir tradizionale e backslopped. È stata inoltre eseguita una correlazione tra il microbiota rilevato e i profili nutrizionali e volatilomi al fine di comprendere meglio il ruolo di ciascun gruppo microbico nella produzione di kefir. Nell'ambito del secondo argomento di questa tesi, è stata valutata l'attività antifungina di sette diversi oli essenziali nei confronti di diversi ceppi di lieviti alterativi, appartenenti a generi diversi, e isolati da diverse matrici alimentari. In particolare, l'attenzione è stata focalizzata sul ruolo potenziale di questi oli essenziali come conservanti naturali contro lieviti alterativi nello yogurt. Questa attività è stata valutata sia in vitro che in vivo producendo uno yogurt su scala di laboratorio. Infine, è stato condotto uno studio sull'uso di metodi cultura dipendenti e cultura indipendenti volti a rilevare e quantificare Brettanomyces spp. come agenti alterativi in diversi vini albanesi.Yeasts have a significant impact on foods by improving their organoleptic properties and promoting health benefits. On the other hand, yeasts are an important cause of spoilage in food industry and it is necessary to enhance the knowledge about yeast spoilage through study and development of techniques aiming to detect and quantify these microorganisms in a quick and easy way. Furthermore, the development of strategies, as the use of natural preservatives, aimed to hamper yeast spoilage are important too. The aim of this Ph.D. thesis is the study of yeasts from two points of view: i) yeasts with a pro-technological role in food industry and ii) yeasts with a detrimental effect on food. Within the first topic, a study about the active role of Saccharomyces cerevisiae and hop in production of nicotinamide riboside, a form of vitamin B3, in craft beers was carried out. This study could be the first step to produce a low alcohol beer with a high vitamin B3 content. Furthermore, a microbial characterization of kefir grains from Bosnia and Herzegovina and their exploitation in traditional vs backslopping methods for kefir production was explored. Kefir grains consist in a symbiotic consortium of lactic acid bacteria, yeasts and acetic acid bacteria embedded within a polysaccharide matrix. The diversity in microbial dynamics, nutritional and volatilome profiles of traditional and backslopped kefir was evaluated too. A correlation among the microbiota detected and the nutritional and volatilome profiles has been also performed in order to better understand the role of each microbial groups within the kefir production. Within the second topic of this thesis the antifungal activity of seven different essential oils was evaluated against several yeast spoilage isolates belonging to different genera and isolated from different food matrices. In particular, the attention has been focused on the potential role of these essential oils as natural preservatives against yeasts spoilage in yogurt. This activity was evaluated both in vitro and in vivo by producing a yogurt in a laboratory scale. Lastly, a study was carried out on the use of culture-dependent and culture-independent methods aimed to detect and quantify Brettanomyces spp. as spoilage agents of several Albanian wines.
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Blumer, Solange Aparecida Groppo. "Enriquecimento com ferro em levedura Saccharomyces cerevisiae." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/11/11141/tde-21112002-161816/.
Full textAbstract:
O objetivo deste trabalho foi estudar a capacidade de adsorção de ferro pela levedura Saccharomyces cerevisiae visando à incorporação em ração animal, utilizando, para isso, o sulfato ferroso. Foram realizados ensaios para determinar a tolerância de uma linhagem de Saccharomyces cerevisiae em concentração de ferro, onde se escolheu uma concentração para estudo de 5,36 mmoles de Fe +2 /L em função de inibição de crescimento e tempo para obtenção de massa satisfatória. Em seguida, foram realizadas cinco fermentações consecutivas para enriquecimento da levedura com Fe +2 , utilizando-se como inoculo todo o fermento recuperado da fermentação anterior descontada a alíquota tomada para a análise do teor de Fe +2 . Uma fermentação com células inativadas termicamente também foi realizada para determinar a capacidade de adsorção de Fe +2 pelas mesmas. Foi observado acúmulo crescente de Fe +2 na levedura a cada fermentação, iniciando-se por 1,43 mmoles de Fe +2 / kg de matéria seca para 6,68 mmoles de Fe +2 / kg de matéria seca após cinco fermentações consecutivas.The aim of this work was to evaluate the iron adsorption capacity of the Saccharomyces cerevisiae yeast, for animal food supplementation purpose. The iron tolerance of one Saccharomyces cerevisiae strain was evaluated, choosing 5.36 mmoles Fe +2 as the concentration for the further assays. Five concecutive fermentation were done for the iron enrichment of the yeast, using as innoculum the whole biomass formed in the previous fermentation except for the amount employed for iron determination. A batch essay with inactive cells was also conducted for the determination of Fe +2 adsorption. Results showed an increasing accumulation of Fe +2 in all fermentation, from 1.43 mmoles kg -1 of dry mass at the beginning, to 6.68 mmoles kg -1 of dry mass, after five consecutive fermentations.
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CAPUSONI, CLAUDIA. "APPLICATION OF NON-CONVENTIONAL YEASTS IN BIOPROCESSES." Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/788442.
Full textAbstract:
Sustainability is one of the most pressing challenge of our century, this term is becoming a main keyword of political agendas and more in general of mass media. To increase the “greenness of bioprocesses”, academia and industry, especially in the biotechnological and chemical fields, are focusing their studies with the scope to shift from traditional organic synthesis to new processes with reduced ecological foot-print. A good way to increase sustainability could be set up bioprocesses exploiting microorganisms. Nowadays, companies are searching new organisms that, differently from the well characterized Saccharomyces cerevisiae, show to be more resistant to the harsh conditions commonly occurring in industrial fermentations (high salt concentration, temperature and pressure). Due to their peculiar features, non-conventional yeasts (NCYs) seem to be a promising solution. On the other hand, the disadvantage to use these new organisms is related to the few studies and literature data available, especially compared to S. cervisiae. To fill this gap researchers have started to characterize these new species.
My PhD work had dual aim:
• First to identify good candidates, with specific physiological properties, that could be exploited in bioprocesses.
• Second to characterize new promising enzymatic activities useful for industrial applications.
In the first studies, I focused my attention on marine yeasts. I chose yeasts isolated from this environment, because their use gives the possibility to perform a seawater-based bioprocess saving large amount of fresh waters, reducing both cost and environmental impact. From our laboratory yeasts collection, I selected, for their halotolerance, two different Debaryomyces hansenii strains. Hence mechanisms involved in osmotic stress response have been investigated employing flow cytometry. I showed that hyper-osmotic stress elicits membrane depolarization and decreases membrane permeability to cationic compounds. This phenomenon reduces ions permeability and can negatively affect the uptake of charged substrate during bioprocesses. My research proceeded with the set up of new fermentation protocols in seawater-based media composed by a mixture of hexose and pentose sugar and cheap nitrogen sources. In these conditions we obtained high biomass yield (0.627) in 40 h of bioprocess.
In the second part of my PhD project, I studied NCYs as sources of enzymes. With this aim I identified a nitrilase of marine strain of Meyerozyma guilliermondii, that displayed high activities on aromatic substrate, but also on arylaliphatic and aliphatic ones. These activities were maintained also in presence of high salts concentration. In particular M. guilliermondii nitrilase was able to perform complete dynamic resolution of mandelonitrile in seawaters within in 8 h.
In the last part of my PhD, I identified a novel extracellular and cell-bound phytase activity in Cyberlindnera jadinii. This enzyme is suitable as feed additive, indeed activities at pH 4.5 and 37°C (animals gastric pH and temperature) were 26.25 mU/mgd.w. and 58.36 mU/mgd.w., detected as extracellular and cell-bound respectively. Phytase activities had their optimum at 50°C, reaching 37.2 mU/mgd.w. (extracellular) and 146 mU/mgd.w. (cell-bound).
Data reported in my PhD work suggest that could be interest to proceed with further characterization on NCYs. New “green” bioprocesses characterized by high productivity could be a key for reach sustainability reducing the ecological impact of industrial production.
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Siebrits, Leoni. "PCR-based DGGE identification of bacteria and yeasts present in South African grape must and wine." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/19865.
Full textAbstract:
Thesis (MSc)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: Wine production involves complex interactions between a variety of yeasts and bacteria. Conventional microbiological methods can be used to identify the different microorganisms present in wine, but prove to be time-consuming and certain microbial species may not grow on synthetic isolation media. The aim of this study was to evaluate the microbial population present in two South African red wines, Pinotage and Merlot, as well as five spoilt commercial South African wines by using a non-culturable approach, polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE). The results from the non-culturable approach were compared to conventional platings. Unique PCR-based DGGE fingerprints were obtained for the Bacteria and yeasts present in the South African Pinotage and Merlot wines. Using yeast specific primers the Pinotage wine showed the presence of non-Saccharomyces yeasts at the beginning of the alcoholic fermentation, while Saccharomyces cerevisiae was present until the completion of the malo-lactic fermentation (MLF). This yeast was also identified during both the alcoholic fermentation and MLF of the Merlot wine using PCR-based DGGE and conventional plating. Using Bacteria specific primers, Lactobacillus plantarum and Lactobacillus sp. was identified in the Pinotage wine using PCR-based DGGE, while Lactobacillus brevis were isolated from Merlot wine using conventional platings. Although the presence of S. cerevisiae is expected during wine fermentation, the presence of this microbe in bottled wine could lead to spoilage. Four of the spoilt commercial wine samples (RW1, RW2, RoW1 and WW1) were found to be spoilt by S. cerevisiae, while a fifth wine sample (RW3) was found to be spoilt by an Acetobacter sp. using PCR-based DGGE. Members of the family Enterobacteriaceae were identified from all the wines using PCR-based DGGE, while Enterobacter sakazakii was identified from RW1 using PCR-based DGGE and conventional plating. The members of the family Enterobacteriaceae could possibly have contributed to the spoilage of the wine by producing undesirable secondary metabolites. PCR-based DGGE proved to be an alternative to conventional microbiological methods for the identification of the microbial species in South African red grape must and wine. This method also proved to be useful in the identification of spoilage microbes in spoilt commercial South African wines.
AFRIKAANSE OPSOMMING: Die produksie van rooi wyn behels komplekse interaksies tussen ‘n verskeidenheid van giste en bakterieë. Konvensionele mikrobiologiese metodes kan gebruik word om die verskillende mikro-organismes wat in rooi wyn teenwoordig is te identifiseer, maar dit blyk tydrowend te wees, terwyl sekere mikro-organismes nie groei op sintetiese media nie. Die doel van hierdie studie was om die mikrobiologiese populasie wat in twee Suid-Afrikaanse rooi wyne, Pinotage en Merlot, en vyf bederfde kommersiële wyne teenwoordig is, te evalueer met die gebruik van ‘n kultuur-onafhanklike benadering, polimerase ketting-reaksie (PKR)-gebaseerde denaturerende gradiënt jel elektroforese (DGJE). Die resultaat van die kultuur-onhafhanklike benadering was vergelyk met konvensionele uitplating tegnieke. Unieke, ongeëwenaarde PKR-gebaseerde DGGE vingerafdrukke was verkry van die Bakterieë en giste aanwesig in die Pinotage en Merlot wyne. Deur gebruik te maak van gis-spesifieke inleiers het die Pinotage wyn die teenwoordigheid van nie-Saccharomyces giste getoon, terwyl Saccharomyces cerevisiae teenwoordig was tot en met die afhandeling van die appel-melksuur gisting (AMG). Hierdie gis is ook geïsoleer gedurende beide die alkoholiese gisting en AMG van die Merlot wyn deur gebruik te maak van PKR-gebaseerde DGGE en konvensionele uitplating tegnieke. Met Bakterieë-spesifieke inleiers, was Lactobacillus plantarum en Lactobacillus sp. geïdentifiseer in die Pinotage wyn deur gebruik te maak van PKR-gebaseerde DGGE, terwyl Lactobacillus brevis geïsoleer is uit Merlot wyn deur gebruik te maak van konvensionele uitplatings. Alhoewel die teenwoordigheid van S. cerevisiae verwag word gedurende wynfermentasie, kan die teenwoordigheid van hierdie mikrobe in gebottelde wyn tot bederwing lei. Vier van die bedorwe kommersiële wynmonsters (RW1, RW2, RoW1 en WW1) was bederf deur S. cerevisiae, terwyl ‘n vyfde wynmonster (RW3) bederf was deur ‘n Acetobacter sp. deur die gebruik van PKR-gebaseerde DGGE. Van al die wyne is lede van die Enterobacteriaceae familie geïdentifiseer deur gebruik gemaak te maak van PKR-gebaseerde DGGE, terwyl Enterobacter sakazakii geïsoleer is van RW1 met konvensionele uitplating. Die lede van die familie Enterobacteriaceae kon moontlik bygedra het tot die bederwing van die wyn deur ongewenste sekondêre metaboliete te produseer. PKR-gebaseerde DGGE bewys ‘n alternatief tot die konvensionele mikrobiologiese metodes vir die identifikasie van die mikrobiese spesies in Suid-Afrikaanse rooi druif mos en wyn te wees. Hierdie metode het ook die bruikbaarheid in die identifikasie van mikrobes wat kommersiële Suid-Afrikaanse wyne bederf, bewys.
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SOUZA, JEFFERSON RODRIGUES DE. "METHOD DEVELOPMENT FOR THE DETERMINATION OF TOTAL SE BY ICP-MS AND ITS SPECIES BY HPLC-ICP-MS IN FOOD SUPPLEMENT AND IN ISOTOPICALLY ENRICHED YEAST." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33733@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
O consumo de suplementos alimentares tem apresentado um aumento significativo nos últimos anos principalmente pelo grande apelo desse produto em relação a complementação da dieta com elementos essenciais e a melhora e manutenção da saúde. A combinação do crescente consumo e o livre acesso a esse produto, aliado a ausência de fiscalização por parte dos órgãos governamentais torna seu consumo descontrolado, um potencial risco a saúde da população. Nesse cenário o desenvolvimento de métodos analíticos destinados ao controle de qualidade incluindo a determinação da concentração de selênio total e de suas espécies torna-se uma necessidade. Para isso, foram desenvolvidas metodologias para a quantificação de selênio total por ICP-MS e suas espécies inorgânicas (Se IV e Se VI) e selenometionina por HPLC-ICP-MS em amostras de suplementos alimentares enriquecidos em selênio e em amostra de levedura enriquecida isotopicamente em 78Se. A metodologia para determinação de selênio total, utilizando diferentes gases de reação, foi otimizada empregando planejamento experimental e os limites de detecção encontrados foram entre 0,01 mg kg(-1) (CH4) e 0,1 mg kg(-1) (NH3) e a concordância com o MRC Selm-1 de entre 99 por cento (NH3) e 104 por cento (CH4). Os resultados encontrados referentes à concentração de selênio nas amostras de suplementos alimentares apresentaram uma discrepância em relação ao valor informado no rótulo entre -29 por cento e +170 por cento e, de maneira complementar, o acoplamento do HPLC ao ICP-MS permitiu realizar a especiação de selênio nas amostras de suplemento alimentar. O emprego das técnicas ICP-MS, HPLC-ICP-MS e ESI-MS possibilitou a caracterização de uma amostra de levedura enriquecida isotopicamente em 78Se em termos de sua distribuição isotópica, concentração de selênio total e selenometionina bem como proteínas com peso molecular de aproximadamente 12 kDa.
The consumption of dietary supplements has a significant increase in recent years mainly for a great appeal of this product in relation to a complementation of the diet with essential elements and an improvement and maintenance of health. The combination of increased consumption and free access to this product, associated to the lack in the inspection by government, makes their consumption uncontrolled and a potential risk to the citizen health. In this scenario the development of analytical methods for quality control, including a determination of the total selenium concentration and its species becomes a primordial necessity. For this, methodologies were developed for quantification of total selenium by ICP-MS and its inorganic species (Se IV and Se VI) and selenomethionine by HPLC-ICP-MS in samples of selenium-based food supplements and in isotopically enriched yeast sample in 78Se. The methodology for total selenium determination was optimized by experimental design and the limits of detection were in the range of 0.01 mg kg(-1) (CH4) and 0.1 mg kg(-1) (NH3) and the agreement with the CRM Selm-1 were between 99 percent (NH3) and 104 percent (CH4). The results found for selenium content in the food supplements samples presented a discrepancy in relation to the labeled value between -29 percent and + 170 percent and, complementarily, coupling of HPLC to ICP-MS allowed an speciation analysis in the food supplements samples. The use of the ICP-MS, HPLC-ICP-MS and ESI-MS techniques enabled a characterization of a 78Se isotopically enriched yeast sample in terms of its isotopic distribution, total selenium concentration and selenomethionine as well as proteins with molecular weight of approximately 12 kDa.
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Cronje, Marise Christine. "Production of kepi grains using pure cultures as starters." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53561.
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Thesis (MSc Food Sc )--Stellenbosch University, 2003.ENGLISH ABSTRACT: Kepi is a refreshing, fermented dairy beverage that differs from other fermented milk products in that it is produced with a mixed microbial community which is confined to discrete grains. These grains can be recovered as a solid matrix at the end of the fermentation and then be reutilised as a starter to ferment the next batch of milk. The grain microbial community consists of a symbiotic association of yeasts and lactic acid bacteria, but the overall composition of the grains has not been completely elucidated. The microbes in the grains are embedded in a protein-polysaccharide Kefiran matrix, which appears essential for grain formation. The mechanism of grain formation is still not fully understood and it thus remains undecided which organism is really responsible for the production of this proteinpolysaccharide matrix. The aim of this study was to isolate, characterise and identify the microbes present in Kefiran from mass cultured South African grains and then to evaluate grain formation with these purified cultures isolated from Kefiran strings using a mass cultivation process. Sixteen strains of lactic acid bacteria and one yeast strain were isolated from Kefiran strings produced during the mass cultivation of South African Kepi grains. API technology, numerical clustering and DNA sequence comparisons were used to identify the purified isolates. The isolates were grouped into seven clusters by numerical clustering and clustering distance from selected reference and marker strains. The heterofermentative lactobacilli were identified as Lactobacillus parakefiri and Lb. kefiri and the homofermentative strains as Lb. delbrueckii ssp. bulgaricus, Lb. gallina rum, Lb. acidophilus and Lb. bavaricus. One isolate was found to be a member of the genus Lactobacillus, but was not positively identified to species level. Cultures isolated from Kefiran were evaluated for ability to grain formation by adding 1 x 109 cfu.ml:' bacteria and 1 x 108 cfu.ml' yeast to double pasteurised, full cream milk during the mass cultivation process. It was found that the control and all the cultures in double pasteurised milk showed grain accumulation indicating that other microbes were present in pasteurised and double pasteurised milk which had an influence on the grain forming ability. The cultures isolated from pasteurised and double pasteurised milk included members of the species Pediococcus, Acinetobacter, Lactococcus laetis ssp. lactis, Candida lipolytica, C. guilliermondii, Chryseobacterium meningosepticum, Pseudomonas putida and four isolates of the Bacillus cereus group. It was found that these rod-shaped "milk isolates" resulted in grain accumulation when inoculated into UHT milk and it was concluded that the "milk isolates" did contribute to grain formation. These isolates were then combined with the Kefiran cultures and this resulted in grains very similar to the traditional Kepi grains. These grains were made from Lb. gallinarum in double pasteurised milk as well with a combination of Lb. gallinarum, Lb. acidophilus, Lb. kefiri, Lb. delbrueckii ssp. bulgaricus, Candida lambica and Pseudomonas putida in URT milk. The grains were firm, elastic and did not dissolve in water but kept their structure and were retained when sieved. An acceptable Kepi beverage was produced from these grains. From these typically traditional grain characteristics it was concluded that, even though the microbial compositions were probably not the same, the general appearance was similar to traditional grains and that it is thus possible to produce grains from pure single strain Kefiran cultures and "milk isolates". Furthermore, it was possible to produce a Kepilike beverage from these grains, which included similar characteristics as the traditional Kepi beverage.
AFRIKAANSE OPSOMMING: Kepi is "n verfrissende, gefermenteerde suiweldrankie wat van ander gefermenteerde produkte verskil in die opsig dat dit vervaardig word deur Kepi korrels in melk te inkubeer. Die Kepi korrels kan aan die einde van die fermentasie herwin word en weer gebruik word om die volgende lot melk te fermenteer. Die korrels bestaan uit "n simbiotiese samestelling van giste en melksuurbakterieë, maar die presiese samestelling van die korrels is steeds onbekend. Die mikro-organismes is vasgevang in "n proteïen-polisakkaried Kefiran matriks en die Kefiran word as essensieel beskou vir korrelvorming. Die meganisme van korrelvorming bly steeds onbekend en daar is nog nie tot "n gevolgtrekking gekom oor watter organisme die Kefiran produseerder is nie. Die doel van die studie was om die mikro-organismes in Kefiran te isoleer en te identifiseer deur Suid-Afrikaanse Kepi korrels te massa kweek. Hierdie mikroorganismes was dan verder geëvalueer ten opsigte van korrel vorming. Sestien melksuurbakterieë isolate en een gis isolaat is geïsoleer vanuit die Kefiran. API tegnologie, numeriese groepering en DNA volgorde vergelykings was gebruik om die isolate te identifiseer. Die isolate is in sewe groepe verdeel volgens numeriese groepering. Die afstand van verwysings en merker organismes is ook in ag geneem. Die heterofermentatiewe organismes is geïdentifiseer as Lactobacillus parakefiri en Lb. kefiri en die heterofermentatiewe organismes as Lb. delbrueckii ssp. bulgaricus, Lb. gallina rum, Lb. acidophilus en Lb. bavaricus. Een isolaat kon nie geïdentifiseer word tot op spesie vlak nie, maar is verwant aan die genus Lactobacillus. Hierdie geïsoleerde Kefiran kulture is geëvalueer ten op sigte van korrelvorming, deur 1 x 109 kve.ml' van die bakterieë en 1 x 108 kve.ml' van die gis by dubbel gepasteuriseerde volroom melk te voeg tydens die massakwekings proses. Die kontrole wat geen bygevoegde kulture bevat nie, sowel as die wat wel bygevoegde kulture bevat, het korrel vorming getoon. Laasgenoemde toon dat daar organismes teenwoordig is in gepasteuriseerde en dubbel gepasteuriseerde melk wat "n rol kan speel tydens korrelvorming. Die kulture wat geïsoleer is vanuit gepasteuriseerde en dubbel gepasteuriseerde melk, sluit in: Pediococcus, Acinetobacter, Lactococcus laetis ssp. lactis, Candida lipolytica, C. guilliennondii, Chryseobacterium menigosepticum, Pseudomonas putida en vier isolate van die Bacillus cereus groep. Hierdie organismes wat uit melk geïsoleer is, het korrelvorming getoon in UHT melk en die gevolgtrekking kan gemaak word dat die "melk organismes" wel "n rol speel tydens korrel vorming. Hierdie "melk isolate" in kombinasie met die Kefiran kulture het korrels tot gevolg gehad wat baie dieselfde was as tradisionele Kepi korrels. Laasgenoemde korrels is gemaak deur Lb. gallina rum in dubbel gepasteuriseerde melk, sowel as deur "n kombinasie van Lb. gallina rum, Lb. acidophilus, Lb. kefiri, Lb. delbrueckii ssp. bulgaricus, Candida lambica en Pseudomonas putida in UHT melk. Die korrels was stewig, elasties, het nie opgelos in water nie en het hulle struktuur behou wanneer gesif. Wanneer hierdie tipiese tradisionele korrels se eienskappe in ag geneem word, kan die gevolgtrekking gemaak word dat alhoewel die mikrobiese samestelling van die korrels nie dieselfde is as die tradisionele korrel nie, is die algemene voorkoms en eienskappe dieselfde en dat dit wel moontlik is om korrels te produseer deur isolate geïsoleer vanuit Kefiran en melk. Verder was dit moontlik om "n drankie te vervaardig met die korrels wat baie dieselfde is as tradisionele Kepi.
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Bui, The Truong, University of Western Sydney, of Science Technology and Environment College, and Centre for Advanced Food Research. "A study of Vietnamese soy sauce fermentation." THESIS_CSTE_CAFR_Bui_T.xml, 2003. http://handle.uws.edu.au:8081/1959.7/635.
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Vietnamese soy sauce has been made for centuries using traditional methods, in villages in Northern Vietnam. This sauce differs from other Asian products not only in its raw materials but also in its flavour characteristics. Presently small scale Vietnamese soy sauce is produced mostly with a standardised inoculum of Aspergillus oryzae under natural conditions. This usually gives rise to a product of variable and inconsistent quality. The aim of this study was to standardise the fermentation condition for the production of Vietnamese soy sauce, so as to obtain a product of more consistently good quality. Aspergillus flavus var columnaris was used as the inoculum. The inoculum was prepared by growing the organism on sticky rice at 20 and 37 degrees centigrade under aerobic conditions. At 20C, a high protease activity was recorded in the inoculum while at 37C, a high amylase activity was observed. The two different inocula prepared at 20C and 37C were then used in the preparation of soy sauce in the normal manner. The inocula were mixed with cooked roasted soy beans and salt water, left to age for 1 month at 30C, followed by ageing at 20C for 2 months. The products obtained were subjected to sensory evaluation and analysed for glucose, fructose, amino acids, nitrogen, ethanol and NaCI. Both inocula produced products of acceptable quality. The inoculum produced at 20C had a higher sensory evaluation score. It also contained a higher level of protein (14.5% compared to 11%), and a higher sensory evaluation score (6.9 compared to 3.2) when compared to a commercial Vietnamese sauce, Hanoi soy sauce. This valuable information will now enable small scale producers to produce this product throughout the year by controlling the temperature, and not be limited to the summer season, as has been the case with the traditional method of production.Master of Science (Hons)
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Braunwald, Teresa [Verfasser], and Wilhelm [Akademischer Betreuer] Claupein. "Feasibility of microbial biodiesel and carotenoid production considering the potential of food processing wastewaters as low cost carbon sources using the example of red yeast Rhodotorula glutinis / Teresa Braunwald. Betreuer: Wilhelm Claupein." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2013. http://d-nb.info/1036921727/34.
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Mogotsi, Lerato Bonolo. "An assessment of the lipopolysaccharide toxicity of rough and smooth escherichia coli strains cultivated in the presence of zygosaccharomyces bailli." Thesis, Bloemfontein : Central University of Technology, Free State, 2011. http://hdl.handle.net/11462/151.
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Thesis (M. Tech. Environmental health) -- Central University of technology, Free State, 2011In nature microorganisms do not exist alone, but in association with one another. These kinds of associations can also be found in food industries, where cells of the same or different species can attach to pipes (biofilm formation) and a variety of surfaces in food processing environments and in food product such as yoghurt which can contain both yeast and bacteria originating from the starter culture as well as fruit. To control food spoilage organisms and food-borne pathogens preventative measures such as good manufacturing processes, the use of sanitizers and preservatives as well as hazard analysis critical control points (HACCP) are crucial in food industries. Sanitation of the working surface, floors, pipes, containers and equipment is a stepwise application of a detergent, acid or alkali rinse, a disinfectant treatment followed by final rinsing. If rinsing of the sanitizer is not done properly it may end up in the product in sub-lethal doses. In this study the influence of Liquid Hypochlorite (LH) and Liquid Iodophore (LI) sanitizers on organism growth and toxicity was evaluated. The organisms investigated included Escherichia coli 0113, Escherichia coli 026 and Zygosaccharomyces bailii Y-1535 in yeast malt broth, which was supplemented with LH and LI at sub-lethal concentrations 0.05% LH, 0.2% LH and 0.075% LI. Subsequently, bacterial and yeast growth responses as pure cultures and in combination (E. coli + Z. bailii) were measured as colony forming units and optical density values. Incorporation of the sanitizers in the growth media resulted in different levels of growth inhibition. Z. bailii proved more robust and the growth rate was not influence significantly by the addition of sanitizers or communal growth with either E. coli strains. The growth rate of both E. coli strains decreased where grown in combination with Z. bailii as well as in the presence of sanitizers, with the most influence exerted by LH. Changes in endotoxicity following the growth of the test samples (stressed cells) and the control (unstressed) were measured by the limulus amoebocyte lysate (LAL) and porcine IL-6 ELISA methods. Where E. coli strains were cultured together with Z. bailii the toxicity of tire mixture showed a decrease over time when measured with the limulus amoebocyte assay method. Interestingly the communal growth of the E. coli strains and Z bailii produced different toxicity profiles when the IL-6 porcine method was used, hi both cases, where E. coli strains were cultured together with Z. bailii the toxicity of the mixture showed an increase over tune when measured by this assay. Other than a similar toxicity profile for E. coli 0113 grown in pure culture, the comparison between results obtained using the LAL or porcine IL-6 methods yielded no correlation in determined toxicity. It was established that LH and LI sanitizers as well as communal growth had an influence in the toxicity of LPS/EPS and the method used to determine such toxicity should be carefully considered.
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Silva, Mariane Daniella da. "Produção de etanol de segunda geração por Saccharomyces cerevisiae ATCC 26602 a partir da hidrólise ácida de sabugo de milho (Zea mays L.)." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153332.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
O milho é uma das culturas mais produzidas no Brasil e durante o seu processamento apresenta como rejeitos o sabugo, caule, folhas e a palha que podem ser utilizados como biomassa para produção de bioetanol de segunda geração. Estima-se que para cada tonelada de milho produzido 2,3 toneladas são rejeitos. Entretanto, para a utilização deste substrato é necessário um tratamento inicial de hidrólise ácida, básica ou enzimática para a remoção da lignina e hemicelulose deixando exposta a celulose, que pode ser utilizada como substrato por microrganismos. Portanto, este trabalho teve como objetivo estudar a produção de etanol pela levedura Saccharomyces cerevisiae ATCC 26602 a partir do sabugo de milho hidrolisado que foi utilizado como substrato. Para isto variaram-se diferentes concentrações de ácido sulfúrico (2,5; 5,0; 7,5 e 10,0%) em diferentes tempos de aquecimento em autoclave (15 e 30 minutos). Foi avaliado o efeito da desintoxicação nos hidrolisados para a remoção de compostos inibidores da fermentação produzidos durante a hidrólise nos diferentes tempos de aquecimento e o efeito de diferentes velocidades de agitação (0, 50 e 100 rpm) na fermentação do hidrolisado. Foi avaliada a produção de etanol utilizando o meio hidrolisado de sabugo de milho (na concentração de 20, 40 e 60 g/L de açúcares redutores). Também foi estimada a produção de etanol utilizando um meio sintético adicionado de glicose (nas concentrações de 40 e 60 g/L) que serviu como padrão de comparação na utilização do meio contendo o sabugo de milho hidrolisado. Os resultados indicaram que a melhor concentração de H2SO4 para realização da hidrólise foi de 2,5% com 30 min. de aquecimento. A desintoxicação do hidrolisado resultou na diminuição da concentração de compostos fenólicos. Foi realizada uma avaliação da produção de etanol após a fermentação de 48 h do hidrolisado, apresentando o melhor resultado em 36 h de fermentação, 7,04 g/L de etanol no meio incubado com agitação de 50 rpm e 8,11 g/L de etanol no meio com agitação de 100 rpm. Portanto, tem-se que o hidrolisado do sabugo de milho é uma opção alternativa para a produção de etanol de segunda geração. Além disso, a levedura S. cerevisiae ATCC 26602 foi capaz de utilizar o hidrolisado sem desintoxicação para produção de etanol.
Corn is one of the most produced crops in Brazil and it can be grown in any soil or climate. During its processing, it presents as tailings the cob, stem, leaves and straw that can be used as biomass for bioethanol production. It is estimated that for each ton of corn produced 2,3 tons are tailings. However, the use of this substrate requires an initial treatment of acidic, basic or enzymatic hydrolysis for the removal of lignin and hemicellulose exposing cellulose, which can be used as a substrate by microorganisms. Therefore, the aim of this research is to study the ethanol production on the yest Saccharomyces cerevisiae ATCC 26602 from hydrolyzed corn cob wich was used as substrate. For this purpose, different concentrations of sulfuric acid (2,5, 5,0, 7,5 and 10,0%) were used under different autoclaving heating periods (15 and 30 minutes). The effect of detoxification on hydrolysates to remove fermentation inhibitor compounds produced during the hydrolysis at the different heating periods and the effect of different stirring rates (0, 50 and 100 rpm) was evaluated in the fermentation of hidrolizate. The ethanol production was evaluated using a hydrolyte environment (at concentration of 40 and 60 g/L). The ethanol production was also evaluated using a synthetic medium added with glucose (at concentrations of 20, 40 and 60 g/L), which will serve as a comparison standard when using the medium containing hydrolyzed corn cob. The results indicate that the best H2SO4 concentration for hydrolysis was 2,50% acid with 30 min. of heating. The detoxification of the hydrolyzates resulted in a decrease on the concentration of phenolic compounds. A partial evaluation of the ethanol production was carried out after fermentation of 48 h of the hydrolyzates, providing the best result within 36 h of fermentation, 7,04 g/L of ethanol in the medium incubated with agitation of 50 rpm and 8,11 g/L ethanol in the medium with 100 rpm stirring. This concludes that corn cob hydrolyzates are an advantageous option for the production of ethanol. Besides, the yest S. cereviseae ATCC 26602 was able to use the hydrolyzate without detoxification for ethanol production.
CNPq: 134033/2016-7
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Patring, Johan. "Development and validation of chromatographic methods to study folate derivatives produced by yeasts /." Uppsala : Dept. of Food Science, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200731.pdf.
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McGrath, Karen. "Selected studies on yeasts isolated from the bakery." Thesis, University of Hertfordshire, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293251.
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Erten, Huseyin. "The production of low alcohol wines by aerobic yeasts." Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/702.
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Souza, Geany Targino de. "Efeitos do óleo essencial de Origanum Vulgare L. sobre o crescimento de bactérias patogênicas e tecnológicas em queijo de coalho." Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/7958.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Coalho cheese is a semi-hard cheese typically produced in the Northeast region of Brazil using an enzymatic coagulating agent and mesophilic lactic acid starter cultures. Some physicochemical characteristics of this product, such as low acidity, high moisture and pH, may favor the survival and growth de pathogenic bacteria frequently associated to food outbreaks. Increasing concerns about the safety of cheeses, have led to the development of alternative preservation techniques using naturally derived ingredients as essential oils (EOs) to ensure the microbiological quality of these products. EO from Origanum vulgare L. (oregano – OVEO) has recognized inhibitory effects against pathogenic bacteria associated to cheeses, however, there is a lack of information regarding the effects of OVEO toward lactic acid bacteria used as starter cultures in processing of these products. Considering these aspects, with the present study aimed to evaluate the effects of OVEO on the cell viabilities of strains Staphylococcus aureus and Listeria monocytogenes, well as of strains Lactococcus spp. used in the processing of coalho cheese. These effects were measured by determination of minimum inhibitory concentration (MIC) of OVEO in microdilution in broth and assessing the viability of pathogenic and starter strains in cheese based broth containing OVEO (0.60 μL.mL-1, 1.25 μL.mL-1, 2.5 μL.mL-1 e 5 μL.mL-1) at 37 °C, 24 h and in semi-solid coalho cheese (0.60 μL.g-1, 1.25 μL.g-1 e 2.5 μL.g-1) at 10 °C during 72 h. The major constituents of OVEO, identified by gas chromatography coupled to mass spectrometry GC-MS were carvacrol (69,0%) and thymol (14.12%). MIC of OVEO was 2.5 μL.mL-1 against both S. aureus and L. monocytogenes and 0.6 μL.mL-1 against the tested starter co-culture. Assays in cheese-based broth containing OVEO at 0.6 μL.mL-1 revealed no decrease in viable cell counts of both pathogenic bacteria, while the starter co-culture decreased 1.0 CFU.mL-1 after 24 h of exposure compared with the initial viable counts. OVEO at 1.25 μL.mL-1 and 2.5 μL.mL-1 caused reductions of up to 2.0 log CFU.mL-1 and 2.5 log CFU.mL-1 in S. aureus and L. monocytogenes, respectively. At these same concentrations, OVEO severely affected the cell viability of the starter co-culture following a short period of exposure. Higher concentrations of OVEO were required to decrease the viable cell counts of all target bacteria in the semi-solid coalho cheese model compared to cheese-based broth. Over the assessed time points, viable cell counts of Lactococcus spp. in coalho cheese containing OVEO were lower than those of S. aureus and L. monocytogenes. These results suggest that the concentrations of OVEO used to control pathogenic bacteria in semi-hard cheese could be carefully evaluated because of their possible inhibitory effects on the growth and survival of starter lactic acid culture used during the production of this product.
O queijo de coalho é um queijo semiduro tipicamente produzido na região Nordeste do Brasil, obtido a partir de agentes enzimáticos coagulantes e/ou pelo uso de bactérias ácido láticas. Algumas características físico-químicas deste produto, como baixa acidez, alta umidade e pH, podem favorecer a sobrevivência e/ou crescimento de bactérias patogênicas associados a surtos alimentares. Crescentes preocupações sobre a conservação de queijos, têm direcionado o desenvolvimento de técnicas de conservação a partir da utilização de ingredientes de origem natural, como óleos essenciais (OEs) para garantir a qualidade microbiológica deste produto. OE de Origanum vulgare L. (orégano - OEOV), possui efeito inibitório reconhecido contra diversas bactérias patogênicas associadas a queijos, no entanto, não existem informações sobre o seu efeito frente as bactérias ácido láticas utilizadas como fermentos no processamento desse produto. Considerando estes aspectos, com o presente estudo objetivou-se avaliar os efeitos do OEOV sobre a viabilidade celular de cepas de Staphylococcus aureus e Listeria monocytogenes, bem como de cepas de Lactococcus spp. utilizadas no processamento de queijo de coalho. Estes efeitos foram medidos pela determinação da Concentração Inibitória Mínima (CIM) do OEOV em microdiluição em caldo, avaliação da viabilidade das cepas patogênicas e bactérias ácido láticas em caldo base queijo contendo OEOV (0,60 μL.mL-1, 1,25 μL.mL-1, 2,5 μL.mL-1 e 5 μL.mL-1) a 37 °C por 24 h e em queijo de coalho semissólido (0,60 μL.g-1, 1,25 μL.g-1 e 2,5 μL.g-1) a 10 °C ao longo de 72 h. Os constituintes majoritários do OEOV identificados por Cromatografia Gasosa acoplada a Espectrometria de Massa (CG-MS), foram carvacrol (69,0%) e timol (14,12%). A CIM do OEOV foi de 2,5 μL.mL-1 frente S. aureus e L. monocytogenes e de 0,6 μL.mL-1 frente Lactococcus lactis subsp. lactis e subsp. cremoris em co-cultura. Nos ensaios em caldo base queijo contendo OEOV a 0,60 μL.mL-1, não ocorreu redução na contagem de células viáveis das bactérias patogênicas. Enquanto que observou-se uma diminuição de 1,0 log UFC.mL-1, nas contagens de células viáveis da co-cultura lática em comparação ao inóculo inicial, após 24 h de exposição. O OEOV a 1,25 μL.mL-1 e 2,5 μL.mL-1 causou redução de até 2,0 log UFC.mL-1 e 2,5 log UFC.mL-1 para S. aureus e L. monocytogenes, respectivamente. Nas mesmas concentrações, após um curto período de exposição o OEOV causou redução brusca na contagem de células viáveis da co-cultura lática. Elevadas concentrações do OEOV foram requeridas para a redução na contagem de células viáveis de todas as bactérias no queijo de coalho semissólido comparado com o caldo base queijo. Ao longo dos tempos avaliados, as contagens de células viáveis de Lactococcus spp. no queijo de coalho contendo OEOV foram menores que as contagens de células viáveis de S. aureus e L. monocytogenes. Os resultados sugerem que concentrações de OEOV usado para controlar bactérias patogênicas em queijo de coalho, devem ser cuidadosamente avaliadas, devido aos seus possíveis efeitos inibitórios sobre o crescimento e sobrevivência das bactérias ácido láticas utilizadas no processamento deste produto.
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McCarthy, Julie-Ann. "The effect of gamma irradiation on yeasts isolated from sausages." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359103.
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Ibn, Hadj Hassine Aziza. "Evaluation de l’activité oestrogenique de contaminants et développement d’un bio-récepteur d’affinité pour la détection d’une xéno-hormone." Thesis, Saint-Etienne, EMSE, 2014. http://www.theses.fr/2014EMSE0740/document.
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Depuis plusieurs années, des agents exogènes environnementaux appelés perturbateurs endocriniens (PE), sont soupçonnés d’interférer avec les fonctions essentielles de reproduction et de développement chez de nombreux organismes vivants. Pour la protection de l’Environnement et de l’Homme, la Directive Cadre sur l’Eau établit des normes de qualité environnementale (NQE) et limite la concentration de trente-trois substances et de huit autres polluants dans les eaux de surface. En revanche, elle ne prend pas encore en compte l’effet de ces substances prioritaires sur les écosystèmes et les humains notamment la perturbation endocrinienne. De plus les spécificités des perturbateurs endocriniens (courbe dose réponse, effets de mélanges etc..) rendent le processus d'identification de ces molécules complexe. Cette thèse est axée sur l’étude d’un des effets hormonaux, les plus couramment rencontrés, la perturbation estrogénique en utilisant comme outils de diagnostic le yeast estrogen screen (YES). Cette étude porte plus particulièrement sur le nord de la Tunisie où l’impact de certains PE sur le développement de poissons Aphanius fasciatus a été mis en évidence. Certains xénoestrogènes comme le cadmium et les HAP, produits générés par l’industrie locale, sont en partie mis en cause dans les malformations observées. En parallèle, certains xénoestrogènes (parabènes notamment) sont retrouvés dans les eaux de stations d’épuration. D’autres produits chimiques comme les colorants textiles et alimentaires ont également des activités endocriniennes. Dans le cadre de la surveillance de la qualité des eaux, il est nécessaire de développer des tests rapides de détection de ces perturbateurs venant complémenter les analyses chimiques. Certaines substances actives sur le système endocrinien étant peu immunogènes, l’axe de recherche développé, dans ce cadre de cette thèse, porte sur un peptide affine pour détecter une myoestrogène, l’ochratoxine AFor several years, environmental exogenous agents called endocrine disruptors (ED) , are thought to interfere with reproduction and development fonctions in many organisms . For the Protection of the Environment and human health, the Water Framework Directive establishes environmental quality standards (EQS) and limits the ranges of thirty-three substances and eight other pollutants in surface waters. Nevertheless, it does not yet take into account the effect of these priority substances on ecosystems and humans including endocrine disruption. More than endocrine disruptors specificity (dose response curve , mixtures effect etc. .. ) make the identification process more complex. This thesis focuses on the study of hormonal effects, the most commonly encountered, estrogen disruption using the yeast estrogen screen (YES) as diagnostic tool. This study focuses particularly on the north of Tunisia, where the impact of ED on development of Aphanius fasciatus . Some xenoestrogens such as cadmium and PAH products generated by local industry are partly implicated on observed skeletal deformities. In parallel, some xenoestrogens (including parabens) are detected in the waters of sewage treatment plants. Other chemicals such as textile and food dyes also have endocrine activities. Under the supervision of water quality, it is necessary to develop rapid tests to detect endocrine disrupter and supplement chemical analyzes. Some active substances on the endocrine system is poorly immunogenic, the research axis developed in this thesis focuses on a peptide affinity for detecting a fungi toxin, ochratoxin A
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Dalton, Hilary Karen. "The yeasts and their chemical changes in the British fresh sausage." Thesis, University of Bath, 1985. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315436.
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Seven hundred and seventeen yeasts isolated from samples of sulphited and unsulphited sausage, skinless sausage, minced beef, and ingredients intended for sausage manufacture, as well as air and equipment in a sausage factory were characterised in detail. Debaryomyces hansenii was the most commonly occurring yeast in the majority of samples of sausage and minced beef, followed by Candida zeylainoides and Pichia membranaefaciens. The presence of sulphite did not appear to influence the overall numbers or range of yeasts in sausage but did affect their relative proportions such that the incidence of D. hansenii was higher and that of certain Cryptoccoccus and Rhodotorula spp. was lower in samples containing the preservative. The heat treatment of skinless sausages during processing appeared to reduce the incidence of D. hansenii. The factory survey showed that the meat intended for sausage manufacture and also other ingredients as well as equipment harboured the same range of yeasts as were found in the finished product. A yeast flora dominated by Trichosporon cutaneum was isolated from pig carcasses immediately following slaughter. This flora was found to be confined largely to the equipment and air of the slaughter area and lairage. In general, the yeast flora of sausage was non-fermentative but could assimilate a wide range of carbohydrates. Selected strains of C. curvata, C. lipolytica var. lipolytica, C. zeylanoides, Cr. albidus, D. hansenii, P. membranaefaciens and Torulopsis candia were shown to synthesise either extra cellular lipases and/or amylases but not proteases in broth culture. Sulphite binding compounds, principally acetaldehyde, were produced in lab lemco broth (pH 7.0) containing sulphite (500 mug g-1) during the exponential phase of growth of representative strains of D. hansenii, C. zeylanoides, P. membranaefaciens and T. candida but not Cr. albidus var. albidus and Rh. rubra. The extent of sulphite binding in minced pork- belly supplemented with sulphite (500 mug g-1) was appreciably greater in samples inoculated with D. hansenii than in those inoculated with representatives of the other members of the microbial association, Brochothrix thermosphacta, Lactobacillus sp. and a pseudomonad. The content of sulphite binding agents in minced pork was found to be positively related (r = 0.98, 0.92 at 1 and 15°C respectively) to the size of the yeast population. The concentration of acetaldehyde in stored sausages obtained from a factory and also those obtained from retail outlets was correlated with the concentration of bound sulphite (r = 0.89). The rate and extent of sulphite binding and acetaldehyde production was fastest during the exponential phase of yeast growth in sausages.
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Roth, Steven M. "Sodium phosphate inhibition of the growth of selected foodborne spoilage yeasts." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/45177.
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Sodium phosphite was evaluated for inhibition of growth of spoilage yeasts in laboratory media and in two commercial carbonated beverages. In addition, the effects of pH and atmosphere in combination with sodium phosphite were also examined in laboratory media. Inhibition studies in laboratory media were performed with optimal or near optimal growth conditions for each yeast. Growth was monitored by measuring optical density at 600 nm. A time to significant growth was determined for experiments in laboratory media and was used to evaluate the effect that sodium phosphite and other test variables had on growth. A time to detectable growth was determined for experiments in commercial carbonated beverages and post incubation counts on observations with undetectable growth were used to evaluate the effects of sodium phosphite on yeast growth. Sodium phosphite was most effective in inhibiting growth of Zygosaccharomyces bailii, and less effective against Saccharomyces cerevisiae, and Saccharomyces uvarum respectively. Results from this investigation show the potential use of sodium phosphite as an antimicrobial food preservative has potential.Master of Science
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Lyness, C. Amanda. "The stability of genetically-modified yeasts in relation to beer of good and consistent quality." Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/1356.
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Price, Elliott. "The influence of yeasts on the aroma of Stilton cheese." Thesis, University of Northampton, 2012. http://nectar.northampton.ac.uk/8877/.
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Fujii, Sachie. "Studies on drying of sugar solutions and stabilization of dried foods by sugars." Kyoto University, 2014. http://hdl.handle.net/2433/189644.
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Tronstad-Elfström, Lisa. "Characterization of Epoxide Hydrolases from Yeast and Potato." Doctoral thesis, Uppsala University, Department of Biochemistry, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5900.
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Epoxides are three-membered cyclic ethers formed in the metabolism of foreign substances and as endogenous metabolites. Epoxide hydrolases (EHs) are enzymes that catalyze the hydrolysis of epoxides to yield the corresponding diols. EHs have been implicated in diverse functions such as detoxification of various toxic epoxides, as well as regulation of signal substance levels.
The main goal of this thesis was to investigate and characterize the α/β hydrolase fold EH. The first part concerns the identifictaion of an EH in Saccharomyces cerevisiae. The second part involves detailed mechanistic and structural studies of a plant EH from potato, StEH1.
Despite the important function of EH, no EH has previously been established in S. cerevisiae. By sequence analysis, we have identified a new subclass of EH present in yeast and in a wide range of microorganisms. The S. cerevisiae protein was produced recombinantly and was shown to display low catalytic activity with tested epoxide substrates.
In plants, EHs are involved in the general defence system, both in the metabolism of the cutin layer and in stress response to pathogens. The catalytic mechanism of recombinantly expressed wild type and mutant potato EH were investigated in detail using the two enantiomers of trans-stilbene oxide (TSO). The proposed catalytic residues of StEH1 were confirmed. StEH1 is slightly enantioselective for the S,S-enantiomer of trans-stilbene oxide. Furthermore, distinct pH dependence of the two enantiomers probably reflects differences in the microscopic rate constants of the substrates. The detailed function of the two catalytic tyrosines was also studied. The behavior of the tyrosine pair resembles that of a bidentate Lewis acid and we conclude that these tyrosines function as Lewis acids rather then proton donors.
The three dimensional structure of StEH1 was solved, representing the first structure of a plant EH. The structure provided information about the substrate specificity of StEH1.
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Casas-Vila, Núria [Verfasser]. "Applications of mass spectrometry-based proteomics: the developmental proteome of D. melanogaster and the RNA-fold interactome of conserved RNA structures in yeast / Núria Casas-Vila." Mainz : Universitätsbibliothek der Johannes Gutenberg-Universität Mainz, 2020. http://d-nb.info/122489653X/34.
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Xiao, Linlin. "Detection of Viable Foodborne Pathogens and Spoilage Microorganisms by Nucleic Acid Amplification Based Platforms." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1308284180.
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SPADOLA, GIORGIO. "CARATTERIZZAZIONE DELLA MICOFLORA ASSOCIATA AI PRODOTTI CARNEI STAGIONATI SUINI CON PARTICOLARE RIFERIMENTO ALLA PRESENZA DI PENICILLIUM NORDICUM ED AL SUO BIOCONTROLLO." Doctoral thesis, Università Cattolica del Sacro Cuore, 2014. http://hdl.handle.net/10280/2474.
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Penicillium nordicum è un importante contaminante di salumi, rappresentanando il 10 % e il 26 % della popolazione di Penicillium spp . isolati , rispettivamente dall'aria e dai prodotti carnei stagionati in un'indagine gestita in Italia ( Battilani et al. , 2007). Diverse colonie di P. nordicum isolate dai salumi hanno dimostrato di essere importanti produttori di ocratossina A , OTA ( Sansom e Frisvad , 2004 . Pietri et al, 2006 ; . Battilani et al , 2010). Attualmente, l'impostazione appropriata delle condizioni ambientali (temperatura, umidità relativa e circolazione dell'aria ), è l'unico strumento accettato per impedire la crescita incontrollata di P. nordicum all'interno degli impianti di stagionatura attraverso una accurata analisi dei punti critici di controllo e l’ideazione di un relativo piano HACCP (Hazard Analysis and Critical Control Points) ben struttutato ( Asefa et al , 2011; Virgili et al , 2012). Anche se il sistema HACCP è stato applicato con successo nel settore alimentare ci sono rischi per la sicurezza alimentare non attentamente considerati. Questo è particolarmente vero per quanto riguarda i rischi micotossigeni associati ai prodotti alimentari di origine animale. Il termine "rischi micotossigeni" è utilizzato da Asefa et al. ( 2011) per descrivere lieviti patogeni e metaboliti secondari tossici prodotti da specie fungine tossigene che contaminano i prodotti alimentari e incidono sulla sicurezza alimentare. La maggior parte dei piani HACCP nelle attività di trasformazione alimentare, come ad esempio la produzione di formaggi e di prodotti carnei stagionati, tiene in considerazione principalmente il rischio derivante da agenti batterici (Arvanitoyannis e Mavropoulos, 2000; Barbuti e Parolari, 2002) anche se tali prodotti alimentari vengono spesso contaminati da funghi micotossigeni e dai loro metaboliti (Spotti et al 1989; Spotti et al , 2001a; Battilani et al 2007). Pertanto, dovrebbe essere cruciale definire un piano HACCP specificamente incentrato sui rischi micotossigeni.
L'identificazione, il controllo e la standardizzazione della micoflora superficie dei salumi è fondamentale per preservare la sicurezza delle produzioni e la salute dei consumatori . Questo è il contesto in cui deve essere valutata l’efficacia e l’affidabilità per l’identificazione delle popolazioni di Penicillium spp di interessante per la produzione alimentare.
In questo contesto , il progetto di ricerca di questa tesi di dottorato ha cercato di approfondire le conoscenze su tali tematiche con l'intento di limitare il rischio micotossigeno nella catena di produzione dei prodotti carnei stagionati.
Sono stati affrontati i seguenti argomenti:
1 . studio della composizione e dinamica della microflora fungina presente sulla superficie dei salumi (prodotto testato, salame) e l'aria di ambienti di stagionatura tenendo conto dell'influenza di alcuni parametri di processo (inoculo starter, temperatura, fase produttiva).
2 . sviluppo di un metodo MALDI TOF MS per l'identificazione di Penicilium a livello di specie per le prospettive future di screening diretti della microflora presente sui salumi.
3 . confronto e integrazione di diverse tecniche, come l'analisi morfologica, l’analisi molecolare e l’analisi tramite spettrometria di massa, per l'identificazione delle specie di Penicillium presenti nei salumi.
4 . valutazione dei lieviti selezionati, isolati dalla superficie di prosciutto crudo, per competere con P. nordicum ed inibire l'accumulo di OTA nella prospettiva del loro uso come starter superficiali con funzione di agenti di biocontrollo.Penicillium nordicum is an important contaminant of cured meat products, representing 10% and 26% of the Penicillium spp. isolated, respectively, from the air or the products in a survey managed in Italy (Battilani et al., 2007). Several P. nordicum cured meat isolates proved to be important producers of ochratoxin A, OTA (Sansom and Frisvad, 2004; Pietri et al., 2006; Battilani et al., 2010). Currently, the appropriate setting of environmental conditions (temperature, relative humidity and air circulation), is the only accepted tool to prevent the uncontrolled growth of P. nordicum inside dry-curing plants through a carefully structured Hazard Analysis Critical Control Point (HACCP) plan (Asefa et al., 2011; Virgili et al., 2012). Even if the HACCP system has been successfully applied in the food industry, there are food safety hazards not carefully considered. This is especially true with regard to mycotoxigenic hazards associated with animal food products. The term “mycotoxigenic hazards” is used by Asefa et al. (2011) to describe pathogenic yeasts and toxic secondary metabolites of toxigenic moulds that contaminate food products and affect food safety. Most HACCP plans in food processing activities, such as the production of cheese and dry-cured meat products, considered mainly bacterial agents (Arvanitoyannis and Mavropoulos, 2000; Barbuti and Parolari, 2002), even if such food products get often contaminated with mycotoxigenic fungi and their metabolites (Spotti et al 1989; Spotti et al., 2001a; Battilani et al 2007). Therefore, it should be crucial to define a HACCP plan specifically focused on the mycotoxigenic hazards. The identification, control and standardization of the surface mycoflora of cured meat products is mandatory to preserve the productions safety and the consumers health. This is the context of the effectiveness and reliability evaluation for the Penicillium spp. identification methods of interesting species for food production. In this context, the research project of this PHD thesis tried to fill some gaps of knowledge with the attempt to limit the mycotoxigenic risk in the cured meat products chain. The following topics were faced: 1. study of the composition and dynamic of fungal microflora present on the surface of cured meat products (salami) and the air of seasoning environments taking into account the influence of some process parameters (starter inoculum, curing temperature, stage of seasoning). 2. development of a MALDI TOF MS method for the identification of Penicilium at species level for future direct screening perspectives of the microflora present on cured meat products. 3. comparison and integration of different techniques, as morphological, molecular and mass spectral analysis, for the identification of Penicillium species in cured meat products. 4. evaluation of selected yeasts, isolated from dry-cured ham surface, to compete with P. nordicum and to inhibit OTA accumulation in the perspective of their use as surface starter biocontrol agents.
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Vijayalakshmi, G. "Some studies on yield & activity of baker’s yeast." Thesis, 1988. http://hdl.handle.net/2009/2247.
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Cheng, Yu-Ting, and 鄭羽莛. "Optimum Carotenoids Production by Isolated Yeast Using Various Food Wastes as Substrates." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/51400674777711284423.
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碩士國立雲林科技大學
環境與安全衛生工程系
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Carotenoids are important natural pigments with antioxidant properties. They are extensively used as coloring agent, food and cosmetic additives and health food. Owing to the concern of health, the demand of natural carotenoids significantly increases in recent years. In this study, three yeast strains (A-1, F-1, G-1) all identified as Rhodotorula mucilaginosa were isolated from the activated sludge tank of the biodiesel plant. Among these strains, strain R. mucilaginosa G-1 and strain R. mucilaginosa F-1 were further selected to investigate effects of environmental conditions, and various carbon sources on carotenoids production. Moreover, the optimum carotenoids extraction method was also studied. The result shows that chemical solvent combined with sonication to extract carotenoids received better extraction efficiency. The optimal carotenoids production of strain R. mucilaginosa F-1 was obtained at pH of 5 under 25oC for 120 hr incubation, and strain R. mucilaginosa G-1 was at pH of 6 under 25oC for 144 hr incubation. The results of carbon sources effect indicated that the carotenoids productions of strain R. mucilaginosa F-1 using molasses, tomato sauce and SzuWu-drink were 2611.04 μg/L, 2234.93 μg/L, 1107.40 μg/L, respectively. Carbon sources and carotenoid productions of strain R. mucilaginosa G-1 were molasses (2444.26. μg/L), tomato sauce (1189.11 μg/L), and SzuWu-drink (936.86 μg/L). The main components of carotenoids produced by strain R. mucilaginosa F-1 and G-1 were β-carotene, torulene and torularhodin.