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Literatura académica sobre el tema "Psychrotrophic bacteria"

Autor: Grafiati

Publicado: 4 de junio de 2021

Última modificación: 20 de febrero de 2023

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Artículos de revistas sobre el tema "Psychrotrophic bacteria"

CHAMPAGNE, C. P., F. GIRARD y N. MORIN. "Inhibition of the Psychrotrophic Bacteria of Raw Milk by Addition of Lactic Acid Bacteria". Journal of Food Protection 53, n.º 5 (1 de mayo de 1990): 400–403. http://dx.doi.org/10.4315/0362-028x-53.5.400.

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Two commercial cultures of lactic acid bacteria (LAB) were added to raw milk in order to inhibit the development of psychrotrophic bacteria. The effects of inoculation level, pH development, media for culture preparation, and milk heat treatment on the inhibitory activity of LAB were studied. Inoculation levels of 2.5 × 106/mL and less of LAB did not significantly reduce psychrotrophic growth. Maximum inoculation level of LAB studied was 25 × 106/mL and this reduced psychrotrophic development by a factor of 10; however, milk pH was reduced to 6.54 over 48 h of incubation at 7°C with this inoculation level. This acidification was not responsible for the inhibitory activity of LAB on psychrotrophs. The LAB were more effective when psychrotroph populations had high multiplication rates. Initial populations of Pseudomonas putida in pasteurized milk did not influence the activity of the LAB. Pseudomonas putida grew faster in sterile milk than in pasteurized milk, but average inhibition rates of LAB were similar in both media.

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Ahmed, S., S. MMR Sumon, MD Hossain, ABM Rubayet Bostami y MM Rahman. "Prevalence of Psychrotrophic Bacteria During Frozen Storage of Raw Milk". Annals of Bangladesh Agriculture 24, n.º 1 (8 de febrero de 2021): 65–76. http://dx.doi.org/10.3329/aba.v24i1.51936.

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The study was aimed to enumerate the load of psychrotrophic bacteria in raw milk stored in freezer. Raw milk was collected from 18 different sized dairy farms located in Gazipur and Mymensingh district. From each location equal number (three of each) of small, medium or large farms were randomly selected. The raw milk samples were stored in freezer (-18 to -22 oC) for 28 days and analyzed for psychrotrophic bacterial load at every 7 days interval. For total viable count, bacteria was grown onto plate count agar at 70C for 10 days. Bacteria grown under such conditions referred as psychrotrophs. However, to determine the type of psychrotrophs selected colonies were grown further onto pseudomonas agar base and gram staining, oxidase, catalase and methyl red test for each isolate were perfomed. The psychrotrophic bacterial load in all the samples were low until 14 days of storage. However, from the third week of storage the bacterial load was observed to increase which reached to as high as 1.1 ± 2.3×107 cfu/mL at the end of the storage period (28 days). The milk samples obtained from large farms were lower (1.3×105 to 6.6×106) than that of medium (1.7×105 to 8.8×106) and small (2.0×105 to 1.1×107) type farms. The bacterial load was significantly (P<0.01) varied among the samples suggesting the heterogeneous management practices in dairy farms. All the morphological and biochemical tests confirmed the isolates as pseudomonas. Based on the present findings, it could be suggested that raw milk can store in the freezer maximum for two weeks in terms of psychrotrophic bacterial load. Ann. Bangladesh Agric. (2020) 24(1) : 65-76

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Malimon, Z., M. Kukhtyn, N. Grynevych y N. Mekh. "Analysis of the insemination of the mesophilic and psychrotrophic microflora of frozen fish". Naukovij vìsnik veterinarnoï medicini, n.º 1(149) (30 de mayo de 2019): 22–29. http://dx.doi.org/10.33245/2310-4902-2019-149-1-22-29.

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The article presents the results of research on the dehiscence of frozen fish with mesophilic and psychrotrophic microflora. Physico-chemical and organoleptic changes which appear in fish during refrigeration are connected with the life of the psychotropic group of microflora, which is more active than mesophilic. Fish are a nutrient medium for the development of microorganisms of all groups, due to its high nutritional and biological value, so the fish are perishable food products, the conditions and terms of their storage require appropriate temperature regimes to stop the development of microorganisms. The aim of the work was carrying out a comparative analysis of insemination of frozen fish with mesophilic and psychrotrophic microflora to make an amend to standards according to microbiological criteria. The microbial number in frozen fish samples was estimated with the temperature of (30 ± 1) ºC incubation of crops for 72 hours (mesophilic microflora) and incubation for 10 days (psychrotrophic microflora) with the temperature (6.5 ± 0.5) ºC. It was identified that there were taken the samples from frozen fish with a quantity of mesophilic bacteria to 102 CFU/g, 1.4-1.8 times (p <0.05) more psychotropic microorganisms. The researched samples with the number of mesophilic microorganisms from 103 to 104 CFU/g were contaminated with psychotropic microflora, which in 1.7-6.8 times (p <0.05) exceeded the content of the mesophilic microflora. With such amount of mesophilic microorganisms, on average of up to 25% of samples, this had a content of psychotrophs of more than 105 CFU/g of fish. According to the content of mesophilic bacteria the samples of frozen fish, which were mathed to a certain norm of 5 × 104 CFU/g, basically in the number of psychrotrophic microflora did not correspond to this indicator, and exceeded it 2 times or more. In the cold period of the year, 63.6 ± 2.1% of frozen fish samples were mesophilic bacteria containing less than 101 CFU/g. At the same time, samples with such content mesophilic bacteria in the warm period of the year was 9.0%, or 7.0 times (p <0.05) less. In addition, in the cold period of the year, only 9.0% of samples were detected, which, according to the content of mesophilic bacteria exceeded the maximum allowable level. At the same time, during the warm period, the number of samples with an excess of mesophilic bacteria content was 27.3 ± 0.3%. Practically the same pattern was observed regarding the insemination of the psychrotrophic microflora in these periods of the year, which was characterized by the fact that in the warm period of the year, frozen fish contains a large number of psychrotrophic microorganisms. Consequently, the results of studies on the amount of microflora in the warm period of the year established 3,0 times (p <0,05) more samples of frozen fish, which, according to the content of mesophilic bacteria, exceeded the maximum permissible level compared with the cold period of the year. It was established that samples of frozen fish containing mesophilic microorganisms less than 101 CFU/g were most unevenly contaminated with psychrotrophic microflora. Among these samples, only 30.1 ± 1.4% were with the number of psychrotrophic microflora less than 101 CFU/g, at the same time, 60.0 ± 0.5% of the samples were contaminated with a psychrotrophic microflora of 101 to 105 CFU/g and 10, 0 ± 0.2% over 105 CFU/g. In the study of frozen fish samples with the number of mesophilic bacteria from 101 to 102 CFU/g revealed a coincidence in the content of psychrotrophs in only 16,7 ± 0,3% of samples, and 33,3 ± 0,3% of fish samples were with the content of psychrotrophic microflora from 102 to 103 CFU/g and 103 to 104 CFU/g and 16.7 ± 0.3% were contaminated with psychrotrophy more than 104 CFU/g. It was established that samples of frozen fish containing mesophilic microorganisms less than 101 CFU/g were most unevenly contaminated with psychrotrophic microflora. Among these samples, only 30.1 ± 1.4% were with the number of psychrotrophic microflora less than 101 CFU/g, at the same time, 60.0 ± 0.5% of the samples were contaminated with a psychrotrophic microflora of 101 to 105 CFU/g and 10, 0 ± 0.2% over 105 CFU/g. In the study of frozen fish samples with the number of mesophilic bacteria from 101 to 102 CFU/g revealed a coincidence in the content of psychrotrophs in only 16,7 ± 0,3% of samples, and 33,3 ± 0,3% of fish samples were with the content of psychrotrophic microflora from 102 to 103 CFU/g and 103 to 104 CFU/g and 16.7 ± 0.3% were contaminated with psychrotrophy more than 104 CFU/g. It was found that that the psychrotrophic microflora of frozen fish is quantitatively predominantly content of mesophilic bacteria several orders of magnitude. During the warm period of the year, more samples of frozen fish were detected in 3,0 times (p <0,05), which, according to the content of mesophilic bacteria, exceeded the maximum permissible level in comparison in the cold period of the year. It was found that 92,6 ± 2,5% of frozen fish samples were in compliance with the requirements of DSTU 4868: 2007. The fish is frozen. At the same time, during the fish evaluation, the contents of the psychrotrophic microflora showed that samples exceeding 5 × 104 CFU/g was in 2.6 times (p <0.05) more than the mesophilic bacteria content. In future the generic and species composition of the psychrotrophic microflora of frozen fish will be studied and the fish evaluating criteria according to the psychrotrophs in order to make corrections according to the microbiological criteria. Key words: frozen fish, psychrotrophic microflora, mesophilic bacteria, contamination, microbial number.

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Munsch-Alatossava, Patricia, Jean-Pierre Gauchi, Bhawani Chamlagain y Tapani Alatossava. "Trends of Antibiotic Resistance in Mesophilic and Psychrotrophic Bacterial Populations during Cold Storage of Raw Milk". ISRN Microbiology 2012 (12 de marzo de 2012): 1–13. http://dx.doi.org/10.5402/2012/918208.

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Psychrotrophic bacteria in raw milk are most well known for their spoilage potential and cause significant economic losses in the dairy industry. Despite their ability to produce several exoenzyme types at low temperatures, psychrotrophs that dominate the microflora at the time of spoilage are generally considered benign bacteria. It was recently reported that raw milk-spoiling Gram-negative-psychrotrophs frequently carried antibiotic resistance (AR) features. The present study evaluated AR to four antibiotics (ABs) (gentamicin, ceftazidime, levofloxacin, and trimethoprim-sulfamethoxazole) in mesophilic and psychrotrophic bacterial populations recovered from 18 raw milk samples, after four days storage at C or C. Robust analysis of variance and non parametric statistics (e.g., REGW and NPS) revealed that AR prevalence among psychrotrophs, for milk samples stored at C, often equalled the initial levels and equalled or increased during the cold storage at C, depending on the AB. The study performed at C with an intermediate sampling point at day 2 suggested that (1) different psychrotrophic communities with varying AR levels dominate over time and (2) that AR (determined from relative amounts) was most prevalent, transiently, after 2-day storage in psychrotrophic or mesophilic populations, most importantly at a stage where total counts were below or around CFU/mL, at levels at which the milk is acceptable for industrial dairy industrial processes.

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Shtenikov, M. D., O. Y. Zinchenko y V. V. Boldyreva. "ANTAGONISTIC ACTIVITY OF MARINE BACTERIA OF BACILLUS, PRIESTIA AND PAENIBACILLUS GENERA OF DIFFERENT THERMOTYPES". Microbiology&Biotechnology, n.º 2(55) (20 de septiembre de 2022): 50–65. http://dx.doi.org/10.18524/2307-4663.2022.2(55).261778.

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SummaryAim. To study the antagonistic activity of bacteria of genera Bacillus, Priestia and Paenibacillus at different conditions of cultivation. Methods. Antagonistically active spore-forming bacteria isolated from deep-sea bottom sediments of the Black Sea were used for the study. Determination of thermotypes was performed using the results of analysis of fatty acid profile parameters. Antagonistic activity to test strains of bacterial opportunistic pathogens was detected by the method of agar blocks on Gauze № 1 and Nutrient Agar media at different cultivation temperatures. Results. Aerobic bacilli of genera Bacillus, Priestia and Paenibacillus of all three thermotypes – thermotolerants, mesophiles and psychrotrophes, in general show lower antagonistic activity when cultured at 37 °C on both media, except for a marked increase in psychrotrophe antagonistic activity at 37 °С on Gauze № 1. Conclusions. It was established that belonging to a certain thermotype affects the character of the antagonistic activity of sporeforming bacteria. The antagonistic activity of mesophilic and thermotolerant bacteria at a higher temperature of cultivation is lower, and that of psychrotrophic bacteria at a higher temperature and on Gauze № 1 medium is higher.

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Verhegghe, M., J. De Block, S. Van Weyenberg, L. Herman, M. Heyndrickx y E. Van Coillie. "Effect of a pre-milking teat foam and a liner disinfectant on the presence of mesophilic and (proteolytic) psychrotrophic bacteria prior to milking". Journal of Dairy Research 86, n.º 4 (noviembre de 2019): 432–35. http://dx.doi.org/10.1017/s0022029919000700.

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AbstractContamination of raw milk by psychrotrophs can lead to the production of heat-resistant proteases and subsequent spoilage of UHT milk. Therefore, this research communication evaluated the effect of a pre-milking teat disinfectant (active components: L-(+)-lactic acid and salicylic acid) and a liner disinfectant (active components: peracetic acid and hydrogen peroxide) on the number of mesophilic and (proteolytic) psychrotrophic bacteria prior to milking. The teat orifices of 10 cows were sampled using a swabbing procedure before and after treatment with a pre-milking teat disinfectant on six subsequent days. On the teat orifices, there was a small but statistically significant decrease in the psychrotrophic bacterial counts between pre and post dipping. No differences were observed for the mesophilic bacterial counts and proteolytic active counts. Liners were also sampled using swabs pre and post disinfection. No statistically significant decrease in the bacterial counts was observed post liner disinfection, although there was a numerical decrease. Sixty-two percent of the proteolytic psychrotrophs were pseudomonads: 16.5% of which were P. fragi, 14.3% P. lundensis, 10.0% P. fluorescens and 2.9% P. putida. Trinitrobenzenesulfonic acid (TNBS) analysis revealed a wide variety in proteolytic activity (from 0 to 55 µmol glycine/ml milk) and the presence of high producers. It can be concluded that there was only a minor effect of teat and liner disinfection on the psychrotrophic bacterial counts indicating that the measures presented did not result in a reduction of the targeted bacteria on teat orifices and liners.

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Przemieniecki, Sebastian Wojciech, Tomasz Paweł Kurowski, Karol Korzekwa y Anna Karwowska. "The effect of psychrotrophic bacteria isolated from the root zone of winter wheat on selected biotic and abiotic factors". Journal of Plant Protection Research 54, n.º 4 (30 de diciembre de 2014): 407–13. http://dx.doi.org/10.2478/jppr-2014-0061.

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Abstract The roots of winter wheat plants, cv. Mikon, grown in 45-year monoculture, were analysed in the study. Twenty-two bacterial isolates obtained from the rhizosphere, rhizoplane, and endorhizosphere that were capable of growth at 8°C and at 28°C, were selected for further analysis. The isolated psychrotrophs accounted for 25% of all bacteria present in the wheat rhizosphere and capable of growth at 8°C. Psychrotrophic bacteria were analysed at a temperature of 10°C and 28°C to determine their ability to inhibit the growth of pathogenic fungi, solubilise mineral phosphates, and to determine their ability to degrade chitin and cellulose. Similarity between the isolates was determined by Enterobacterial Repetitive Intergenic Consensus – Polymerase Chain Reaction (ERIC-PCR) and Random Amplification of Polymorphic DNA – Polymerase Chain Reaction (RAPD-PCR). The majority of isolated psychrotrophs inhibited the growth of pathogenic fungi and solubilised mineral phosphates at both incubation temperatures. Psychrotrophic bacteria exerted a two-fold stronger inhibitory effect on mycelial growth at 10°C than at 28°C. The growth of Fusarium culmorum and F. oxysporum was inhibited to the highest extent at 10°C and at 28°C, respectively. Phosphate solubilisation rates were higher at 28°C, particularly in the rhizosphere. Regardless of temperature, the bacteria exhibited low chitin-degrading potential, and none of the isolates was capable of degrading cellulose. A high similarity between the selected psychrotrophs was revealed by ERIC-PCR and RAPD- -PCR analyses. Based on RAPD-PCR, the analysed population was divided into a group of isolates obtained from the rhizosphere, and two groups comprising representatives of both the rhizoplane and the endorhizosphere. Due to their ability to grow over a wide temperature range and increase phosphorus availability to plants, and their antagonism against pathogens, psychrotrophic bacteria can be used to improve the growth and yield of cereal crops.

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Teider Junior, Pedro I., José C. Ribeiro Júnior, Eric H. Ossugui, Ronaldo Tamanini, Juliane Ribeiro, Gislaine A. Santos, Amauri A. Alfieri y Vanerli Beloti. "Pseudomonas spp. and other psychrotrophic microorganisms in inspected and non-inspected Brazilian Minas Frescal cheese: proteolytic, lipolytic and AprX production potential". Pesquisa Veterinária Brasileira 39, n.º 10 (octubre de 2019): 807–15. http://dx.doi.org/10.1590/1678-5150-pvb-6037.

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ABSTRACT: The most consumed cheese in Brazil, Minas Frescal cheese (MFC) is highly susceptible to microbial contamination and clandestine production and commercialization can pose a risk to consumer health. The storage of this fresh product under refrigeration, although more appropriate, may favor the growth of spoilage psychrotrophic bacteria. The objective of this study was to quantify and compare Pseudomonas spp. and other psychrotrophic bacteria in inspected and non-inspected MFC samples, evaluate their lipolytic and proteolytic activities and their metalloprotease production potentials. Twenty MFC samples were evaluated: 10 inspected and 10 non-inspected. Counts of psychrotrophic bacteria and Pseudomonas spp., evaluation of the proteolytic and lipolytic potential of the isolates, and identification of potential producers of alkaline metalloprotease (AprX) were assessed. The mean total psychrotrophic counts were 1.07 (±2.18) × 109CFU/g in the inspected samples and 4.5 (±5.86) × 108CFU/g in the non-inspected, with no significant difference (p=0.37). The average score of Pseudomonas spp. was 6.86 (±18.6) × 105 and 2.08 (±3.65) × 106 CFU/g for the inspected and non-inspected MFC samples, respectively, with no significant difference (p=0.1). Pseudomonas spp. represented 0.06% and 0.004% of psychrotrophic bacteria found in inspected and non-inspected MFC samples, respectively. Collectively, 694 psychrotrophic strains and 47Pseudomonas spp. were isolated, of which 59.9% and 68.1% were simultaneously proteolytic and lipolytic, respectively. Of the 470 psychrotrophs isolated from inspected and 224 from non-inspected cheese samples, 5.74% and 2.23% contained aprX, respectively, while 100 and 86.96% of the Pseudomonas spp. isolates in inspected and non-inspected cheese samples contained the gene. The production potential of AprX did not, however, determine the proteolytic activity on plates of these isolates under the conditions evaluated in this study. Of total, 65.63% of the psychrotrophs that contained aprX gene were confirmed as Pseudomonas spp., using genus-specific PCR. Phylogenetic analysis of the 16S rRNA gene of the other psychrotrophs that were potential producers of AprX identified them as Serratia spp. (n=7), Raoultella ornithinolytica (n=1), and Acinetobacter schindleri (n=1) in the inspected samples and Psychrobacter sanguinis (n=1) and Leuconostoc mesenteroides (n=1) in the non-inspected samples. The production conditions of Brazilian MFC of these samples, while meeting the legal determinations, are not sufficient to control Pseudomonas and other spoilage-related psychrotrophs. Thus, stricter hygienic measures are required during the formal production of this type of cheese.

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Hantsis-Zacharov, Elionora y Malka Halpern. "Culturable Psychrotrophic Bacterial Communities in Raw Milk and Their Proteolytic and Lipolytic Traits". Applied and Environmental Microbiology 73, n.º 22 (21 de septiembre de 2007): 7162–68. http://dx.doi.org/10.1128/aem.00866-07.

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ABSTRACT During cold storage after milk collection, psychrotrophic bacterial populations dominate the microflora, and their extracellular enzymes, mainly proteases and lipases, contribute to the spoilage of dairy products. The diversity, dynamics, and enzymatic traits of culturable psychrotrophs in raw milk from four farms were investigated over a 10-month period. About 20% of the isolates were found to be novel species, indicating that there is still much to be learned about culturable psychrotrophs in raw milk. The psychrotrophic isolates were identified and classified in seven classes. Three classes were predominant, with high species richness (18 to 21 species per class) in different seasons of the year: Gammaproteobacteria in spring and winter, Bacilli in summer, and Actinobacteria in autumn. The four minor classes were Alphaproteobacteria, Betaproteobacteria, Flavobacteria, and Sphingobacteria. The dominant classes were found in all four dairies, although every dairy had its own unique “bacterial profile.” Most but not all bacterial isolates had either lipolytic or both lipolytic and proteolytic activities. Only a few isolates showed proteolytic activity alone. The dominant genera, Pseudomonas and Acinetobacter (Gammaproteobacteria), showed mainly lipolytic activity, Microbacterium (Actinobacteria) was highly lipolytic and proteolytic, and the lactic acid bacteria (Lactococcus and Leuconostoc) displayed very minor enzymatic ability. Hence, the composition of psychrotrophic bacterial flora in raw milk has an important role in the determination of milk quality. Monitoring the dominant psychrotrophic species responsible for the production of heat-stable proteolytic and lipolytic enzymes offers a sensitive and efficient tool for maintaining better milk quality in the milk industry.

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Whyte, Lyle G., Charles W. Greer y William E. Inniss. "Assessment of the biodegradation potential of psychrotrophic microorganisms". Canadian Journal of Microbiology 42, n.º 2 (1 de febrero de 1996): 99–106. http://dx.doi.org/10.1139/m96-016.

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Bioremediation of polluted temperate and cold temperature environments may require the activity of psychrotrophic bacteria, because their low temperature growth range parallels the ambient temperatures encountered in these environments. In the present study, 135 psychrotrophic microorganisms isolated from a variety of ecosystems in Canada were examined for their ability to mineralize14C-labelled toluene, naphthalene, dodecane, hexadecane, 2-chlorobiphenyl, and pentachlorophenol. A number of the psychrotrophic strains mineralized toluene, naphthalene, dodecane, and hexadecane. None of the psychrotrophs were capable of mineralizing 2-chlorobiphenyl or pentachlorophenol. Those strains demonstrating mineralization activity were subsequently screened by the polymerase chain reaction (PCR) and Southern hybridization of PCR products for the presence of catabolic genes (alkB, ndoB, todC1, and xylE) involved in known bacterial biodegradative pathways for these compounds. Some of the psychrotrophs able to mineralize toluene and naphthalene possessed catabolic genes that hybridized to xylE or todC1, and ndoB, respectively. The alkB PCR fragments obtained from the strains that mineralized dodecane and hexadecane did not hybridize to an alkB gene probe derived from Pseudomonas oleovorans. Psychrotrophic strain Q15, identified as a Rhodococcus sp., also mineralized the C28n-paraffin octacosane. A gene probe constructed from the "alkB" PCR fragment from strain Q15 did hybridize with the alkB PCR fragments from most of the psychrotrophic alkane biodegraders, indicating that the alkB primers may be amplifying another gene(s), perhaps with low homology to P. oleovorans alkB, which may be involved in the biodegradation of both short chain (dodecane) and longer chain alkanes (hexadecane, octacosane). All of the psychrotrophic biodegradative isolates examined were capable of mineralization activity at both 23 and 5 °C, indicating their potential for low temperature bioremediation of petroleum hydrocarbon contaminated sites.Key words: psychrotrophic microorganisms, biodegradation, catabolic gene probes, organic pollutants.

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Tesis sobre el tema "Psychrotrophic bacteria"

McCarthy, Conor Neil y n/a. "Regulatory Elements Controlling Lipase and Metalloprotease Production in Pseudomonas fluorescens B52". Griffith University. School of Health Science, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20031015.124744.

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Psychrotrophic bacteria, such as Pseudomonas fluorescens B52, are a major cause of milk spoilage at refrigeration temperature due to the production of lipolytic and proteolytic enzymes. Regulatory mechanisms controlling the production of lipase and protease by the B52 lipA and aprX genes were investigated. Transposon mutagenesis identified the possible involvement of a poly-A polymerase enzyme which destabilises mRNA by 3' polyadenylation. A homologue of the E. coli EnvZ/OmpR two-component sensor/regulator system was identified by transposon mutagenesis and shown to repress lipase and protease production. This system responds to Na+ and K+ concentration in E. coli and these ions were also shown to repress lipase and protease expression in B52, however the EnvZ/OmpR system is not solely responsible for this. Assays of translational lacZ fusions with aprX and lipA were used to speculate on the mechanism by which Na+ and EnvZ/OmpR repress the aprX-lipA operon. A membrane-bound sensor, MspA, which regulates protease production in P. fluorescens LS107d₂, was shown to exist in B52 but mutagenesis of the B52 mspA gene had no effect on lipase and protease expression. A homologue of the P. fluorescens CHA0 rsmA gene, encoding an RNA-binding translation repressor, was found in B52. Although aprX and possibly lipA contain consensus sequences for RsmA, mutagenesis of rsmA had no significant effect on lipase and protease expression. Repression of lipase and protease expression by Na+ was increased by expression of the P. fluorescens M114 pbrA sigma-factor gene in B52.

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McCarthy, Conor Neil. "Regulatory Elements Controlling Lipase and Metalloprotein Production in Pseudomonas fluorescens B52". Thesis, Griffith University, 2003. http://hdl.handle.net/10072/367432.

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Psychrotrophic bacteria, such as Pseudomonas fluorescens B52, are a major cause of milk spoilage at refrigeration temperature due to the production of lipolytic and proteolytic enzymes. Regulatory mechanisms controlling the production of lipase and protease by the B52 lipA and aprX genes were investigated. Transposon mutagenesis identified the possible involvement of a poly-A polymerase enzyme which destabilises mRNA by 3' polyadenylation. A homologue of the E. coli EnvZ/OmpR two-component sensor/regulator system was identified by transposon mutagenesis and shown to repress lipase and protease production. This system responds to Na+ and K+ concentration in E. coli and these ions were also shown to repress lipase and protease expression in B52, however the EnvZ/OmpR system is not solely responsible for this. Assays of translational lacZ fusions with aprX and lipA were used to speculate on the mechanism by which Na+ and EnvZ/OmpR repress the aprX-lipA operon. A membrane-bound sensor, MspA, which regulates protease production in P. fluorescens LS107d2, was shown to exist in B52 but mutagenesis of the B52 mspA gene had no effect on lipase and protease expression. A homologue of the P. fluorescens CHA0 rsmA gene, encoding an RNA-binding translation repressor, was found in B52. Although aprX and possibly lipA contain consensus sequences for RsmA, mutagenesis of rsmA had no significant effect on lipase and protease expression. Repression of lipase and protease expression by Na+ was increased by expression of the P. fluorescens M114 pbrA sigma-factor gene in B52.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Health Sciences
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Suzuki, Takeshi. "Enzymological Studies of Cold-active Esterases from Psychrotrophic Bacteria". Kyoto University, 2003. http://hdl.handle.net/2433/149012.

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Gauthier, Elisabeth. "Utilization of low molecular weight substrates by psychrotrophic meat spoilage organisms". Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59274.

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Four meat spoilage organisms were grown at 4$ sp circ$C for 7 d, in an aqueous extract of meat (Meat Juice Medium), and the levels of various nutrients in the extracts were measured. At an agitation rate of 50 rev$ cdot$min$ sp{-1},$ the four species reached viable counts of 10$ sp8$ Colony Forming Units (CFU)$ cdot$ml$ sp{-1},$ and the order of nutrient utilization was as follows: (1) glucose, (2) gluconate and urea, (3) glycerol, (4) glucose-6-phosphate. Several substrates were still present in the growth medium at the end of the growth period, namely lactate, glucose-6-phosphate and the two unknowns. At a higher agitation rate (100 rev$ cdot$min$ sp{-1}),$ the non-fluorescent pseudomonad reached final counts of ca. 10$ sp{10}$ CFU$ cdot$ml$ sp{-1},$ 2 logs higher than those of the other three organisms present in the mixed culture. The order of nutrient utilization was: (1) glucose, (2) gluconate, urea and glycerol, (3) lactate and glucose-6-phosphate, (4) unknowns 1 and 2. At day 7, none of the nine substrates studied remained in the growth medium.

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Rasmussen, David Dean. "The Effectiveness of Potassium Lactate and Lactic Acid Against Campylobacter Species and Psychrotrophic Bacteria". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35318.

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This study examined the efficacy of potassium lactate and lactic acid to control Campylobacter sp. and psychrotrophic bacteria on chicken. The objectives of the two studies conducted were to determine the optimal combination of potassium lactate and lactic acid to inhibit Campylobacter sp. in a challenge study and to inhibit naturally occurring Campylobacter sp. and psychrotrophic bacteria in a shelf life study.

Boneless, skinless chicken breasts were injected with three levels of potassium lactate (0,1.5,2%), in conjunction with four levels of lactic acid. Lactic acid was injected (0, 0.1, 0.2, 0.3%) as well as applied directly to the surface (0.1% of weight of chicken breast). The chicken breasts were surface inoculated with a mixture of Campylobacter sp. and sampled over a period of 28 days at 11oC. The greatest inhibition was found using 2% potassium lactate in conjunction with any level of lactic acid (injected) or 0.1% lactic acid (surface application). Results of this study indicate that potassium lactate and lactic acid can be used to control the growth and/or survival of Campylobacter sp. on boneless chicken breasts.

The second study eliminated the 1.5% potassium lactate and 0.2% and 0.3% lactic acid treatments and chicken breasts were not inoculated with Campylobacter sp.. This 4oC shelf life study occurred over 32 days, testing for Campylobacter species, psychrotrophic bacteria, as well as testing for sensory perceptions of color and odor changes in the chicken. The most effective treatment was the 2% potassium lactate-0.1% lactic acid surface treatment, demonstrating the most inhibition against both target populations. This treatment also had the greatest impact upon the odor of the chicken breasts. This treatment had the greatest difference from control samples, which was achieved by the inhibition of spoilage organisms on the chicken breasts.
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Fitzgerald, Laura Emma. "The application of microfiltration as a partial sterilisation technique for the reduction of psychrotrophic spore forming bacteria from viscous dairy feeds". Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582874.

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The use of microfiltration as an alternative to pasteurisation to reduce the microbial load of raw skimmed milk is a well established technology. However, its application in reducing bacteria from highly viscous dairy based solutions has not due to issues of low flux and high fouling tendency. This study involves the application of microfiltration to remove spores from high solids content Milk Protein Isolate (MPI) solutions. MPI feeds were inoculated with Bacillus mycoides spores a safer alternative to Bacillus cereus, a psychrotrophic spore forming bacteria found in dairy feeds. Suitable protocols for MPI resolubilisation, Bacillus mycoides cell and spore preparations were established and the membranes, MPI and spores were fully characterised by scanning electron microscopy (SEM), particle size distribution, rheology and pure water flux (PWF) measurements. Feed and permeate samples collected during experiments were analysed for solids content by oven drying, protein content using the Bradford assay and spore content using PetrifilmTM Aerobic count plates. To try and determine an optimum protocol for MPI filtration, a variety of filtration rig set-ups, modules and membranes were tested. Experiments were carried out at different MPI concentrations (4 – 16 wt%), cross flow velocities (CFV’s) (0.7 – 2.0 m s-1) and transmembrane pressures (TMP’s ) (1 and 2 bar). The filtration of 15 wt% MPI proved challenging. The best set of results were obtained using the 12.0 μm membrane at 1.4 m s-1, producing a 27 LMH flux, 96.5% protein transmission and a 2.1 log spore reduction. These results indicate that large pore ceramic microfiltration may be a suitable technology to replace or augment pasteurisation for high solids content dairy feeds. The effect of backwashing using different durations and frequencies was investigated. Backwashing parameters of 10 seconds every 5 minutes at 1 bar were found to be the most effective. The optimum cleaning regime found for MPI fouled ceramic membranes involved a long rinsing backflush at 1 bar, acid and alkali steps without backwashing, which produced a 99.6% flux recovery.

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Voges, Joana Gerent. "Qualidade microbiológica da água e do leite e ocorrência de Leite Instável Não Ácido (LINA) em propriedades de agricultura familiar do Planalto Norte de Santa Catarina". Universidade do Estado de Santa Catarina, 2015. http://tede.udesc.br/handle/handle/954.

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Milk production is an important income for family farmers, but to act competitively in the market the dairy sector needs to raise the quality of its raw material. The study aimed to evaluate the factors that influence water quality and milk quality and unstable non-acid milk (UNAM) occurrence in family farms of Planalto Norte of Santa Catarina, Brazil. The study also aimed to assess the influence of water quality used in farm on the milk quality, and to establish relation between bacterial contamination and concentration of CMP in milk. The farms were characterized by a semi-structured questionnaire guide. Samples were collected for analysis of milk composition, somatic cell count (SCC), total bacterial count (TBC) and psychrotrophic bacterial count (PBC). It carried out the alcohol test, titratable acidity and pH, and CMP index was determined by high-performance liquid chromatography. Analyzes performed in water were CBP, Escherichia coli, coliforms at 35ºC and mesophilic aerobic. The food offered to animals also were analyzed. Data were subject to factor and cluster analysis, and broken-line model analysis using SAS statistical package. The most appropriate strategies of animal feed, with consequent improvement of animal productivity and increase of lactose content in milk were related to a lower occurrence of UNAM, which had little relation with farm structure and with season. The farm structure also had little influence on milk microbiological quality. Already the milking management influenced the bacterial contamination, and these were related to CMP concentration in milk. The water quality used in dairy farms was not related to milk quality. Rainfall and water source affected the microbiological contamination in water
A produção de leite é uma importante fonte de renda para agricultura familiar, mas para atuar de modo competitivo no mercado o setor lácteo precisa elevar a qualidade da sua matéria-prima. O estudo objetivou avaliar os fatores que influenciam na qualidade da água e do leite e na ocorrência de leite instável não ácido (LINA) em propriedades de agricultura familiar do Planalto Norte de Santa Catarina. O trabalho também objetivou verificar a influência da qualidade da água utilizada na propriedade sobre a qualidade do leite produzido, além de estabelecer a relação entre a contaminação bacteriana e a concentração de caseinomacropeptídeo (CMP) no leite. As propriedades foram caracterizadas por meio de um questionário guia semi-estruturado. Foram coletadas amostras de leite para analisar sua composição, contagem de células somáticas (CCS), contagem bacteriana total (CBT), e contagem de bactérias psicrotróficas (CBP). Realizou-se o teste do álcool, análises de acidez titulável e pH, e determinou-se o índice CMP por cromatografia líquida de alta eficiência. Na água, foram realizadas análises de CBP, Escherichia coli, coliformes a 35ºC e aeróbios mesófilos. Também foram analisados os alimentos oferecidos aos animais. Os dados foram submetidos à análise fatorial e de agrupamento, e regressão segmentada (broken-line) utilizando o pacote estatístico SAS. As estratégias mais adequadas de alimentação animal, com consequente melhoria da produtividade e aumento do teor de lactose no leite, tiveram influência na menor ocorrência de LINA, que por sua vez apresentou pouca relação com a infra-estrutura das propriedades e com as estações do ano. A infra-estrutura das propriedades também teve pouca relação com a qualidade microbiológica do leite. Já o manejo de ordenha mostrou influência na contaminação bacteriana, que relacionou-se com a concentração de CMP no leite. A qualidade da água utilizada nas propriedades leiteiras não apresentou relação com a qualidade do leite. A precipitação pluviométrica e a origem da água afetaram a sua contaminação microbiológica

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Cardoso, Rodrigo Rezende. "Influência da microbiota psicrotrófica no rendimento de queijo Minas Frescal elaborado com leite estocado sob refrigeração". Universidade Federal de Viçosa, 2006. http://locus.ufv.br/handle/123456789/5390.

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The raw milk storage under cooling temperatures selects the psychrotropic bacteria growth including species able to produce heat resistant proteases and lipases that are usually associated with milk quality deterioration. The decrease in the cheese production yield is an important problem associated with the psychrotrophic bacteria growth in the refrigerated raw milk. This work aimed to evaluate the relation between the psychrotrophic bacteria population present in the cooled raw milk and the yield of Minas Frescal cheese production. The raw milk was stored at 10 °C, for up to four days, it was pasteurized, and daily used for the Minas Frescal cheese production. Concomitantly, the number of psychrotrophic, proteolytic and lipolytic psychrotrophic bacteria and protease and lipase activity was evaluated in the raw milk. The raw milk maintenance at 10 °C made possible the psychrotrophic bacteria growth, with an increase of two logarithmic cycles in the proteolytic psychrotrophic bacteria population and of, approximately, three logarithmic cycles in the lipolytic psychrotrophic bacteria population, after four days of storage. The protease and lipase activities increased during the refrigerated raw milk storage, presenting superior values to the ones of the recently milked milk. A decrease of 6.78% in liters of milk per kg of cheese and 6.38 % in grams of total solids of cheese per liter of milk when the product was done with cooled milk stored for four days, was observed. The psychrotrophic bacteria number present in that milk varied from 108 CFU mL-1 to 109 CFU mL-1, and the proteolytic and lipolytic psychrotrophic bacteria populations were higher than 107 CFU mL-1. For the same storage period, an increase in the total nitrogen, fat and total solids concentrations in the serum from the Minas Frescal cheese production, was verified. It was estimated that, for an industry able to process 50.000 liters of milk per day, designating 33% of this amount to produce Minas Frescal cheese, the economic losses associated with the decrease in the cheese production are estimated in US$ 15,480.00 per month.
A estocagem do leite cru sob refrigeração favorece a seleção de bactérias psicrotróficas, incluindo espécies produtoras de proteases e lipases termorresistentes que são associadas à perdas de qualidade do leite e seus derivados. Para as indústrias de queijos, um dos principais problemas causados em decorrência da contaminação e do crescimento de bactérias psicrotróficas no leite cru refrigerado é a redução do rendimento durante a fabricação. O objetivo deste trabalho foi relacionar o rendimento do queijo Minas Frescal com a população de bactérias psicrotróficas no leite cru refrigerado granelizado. O leite cru foi estocado a 10 °C, por até quatro dias, posteriormente pasteurizado e, diariamente, utilizado para a fabricação de queijo Minas Frescal. Paralelamente, foram quantificadas as microbiotas psicrotrófica, psicrotrófica proteolítica e lipolítica e a atividade proteolítica e lipolítica do leite cru. A manutenção do leite cru a 10 °C possibilitou um crescimento da microbiota psicrotrófica, com um aumento de dois ciclos logarítmicos na população de bactérias psicrotróficas proteolíticas e de, aproximadamente, três ciclos logarítmicos na população de bactérias psicrotróficas lipolíticas, após quatro dias de estocagem. As atividades proteolítica e lipolítica aumentaram durante a estocagem do leite cru refrigerado, apresentando valores superiores aos do leite recém-ordenhado. Foi constatada uma redução de 6,78 % no rendimento em termos de litros de leite por quilograma de queijo e de 6,38 % em gramas de sólidos totais no queijo por litro de leite quando o queijo Minas Frescal foi fabricado com leite refrigerado armazenado por quatro dias. O leite cru que resultou nestas perdas de rendimento apresentava uma população de 108 UFC mL-1 a 109 UFC mL-1 de bactérias psicrotróficas e a população de bactérias psicrotróficas proteolíticas e lipolíticas era superior a 107 UFC mL-1. Verificou-se ainda, para o mesmo período de estocagem, um aumento das concentrações de nitrogênio total, gordura e sólidos totais no soro proveniente da fabricação do queijo Minas Frescal. As perdas econômicas decorrentes da redução do rendimento da fabricação de queijo Minas Frescal foram estimadas em US$ 15,480.00 por mês, para uma indústria de laticínios processadora de 50.000 litros de leite por dia e que destine 33% do leite captado a fabricação de queijo Minas Frescal.

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Kawamoto, Jun. "Studies of cold-adaptation mechanism of a psychrotrophic bacterium, Shewanella livingstonensis Ac10". Kyoto University, 2008. http://hdl.handle.net/2433/136582.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第13493号
農博第1670号
新制||農||951(附属図書館)
学位論文||H20||N4318(農学部図書室)
UT51-2007-T869
京都大学大学院農学研究科応用生命科学専攻
(主査)教授江﨑信芳, 教授清水昌, 教授阪井康能
学位規則第4条第1項該当

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Park, Jung ha. "Studies of cold-inducible inner membrane proteins of a psychrotrophic bacterium, Shewanella livingstonensis Ac10". Kyoto University, 2012. http://hdl.handle.net/2433/157717.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第16926号
農博第1942号
新制||農||1001(附属図書館)
学位論文||H24||N4687(農学部図書室)
29601
京都大学大学院農学研究科応用生命科学専攻
(主査)教授栗原達夫, 教授喜多恵子, 教授阪井康能
学位規則第4条第1項該当

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Libros sobre el tema "Psychrotrophic bacteria"

Psychrotrophic bacteria in foods: Disease and spoilage. Boca Raton: CRC Press, 1992.

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Brown, Steven A. Screening for plasmid DNA in an exopolymer-producing psychrotrophic bacterium. Sudbury, Ont: Laurentian University, 1987.

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Andrews, Shelley Ann. Purification and initial chemical characterization of an exopolymer produced by a psychrotrophic bacterium. Sudbury, Ont: Laurentian University, 1991.

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Mondal, Abdul Alim. Studies on the identity of the stimulatory material for exopolymer production, in a psychrotrophic bacterium. [s.l: s.n.], 1992.

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Meer, Ralph R. Identification and characterization of some psychrotrophic heat resistant/sporeforming bacteria in the Grade A raw milk supply of Oregon. 1987.

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Capítulos de libros sobre el tema "Psychrotrophic bacteria"

Brasca, Milena, Marilù Decimo, Stefano Morandi, Solimar Gonçalves Machado, François Bagliniére y Maria Cristina Dantas Vanetti. "Psychrotrophic bacteria". En Microbiology in Dairy Processing, 37–61. Chichester, UK: John Wiley & Sons Ltd and the Institute of Food Technologists, 2017. http://dx.doi.org/10.1002/9781119115007.ch3.

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Borker, Shruti Sinai, Swami Pragya Prashant, Anu Kumari, Sareeka Kumari, Rajni Devi y Rakshak Kumar. "Metabolic Pathways in Biodegrading Psychrotrophic Bacteria Under Cold Environments". En Extreme Environments, 217–33. First edition. | Boca Raton : CRC Press, 2021.: CRC Press, 2021. http://dx.doi.org/10.1201/9780429343452-13.

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McMeekin, T. A. "Preliminary observations on psychrotrophic and psychrophilic, heterotrophic bacteria from antarctic water samples". En Biology of the Vestfold Hills, Antarctica, 35–40. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-3089-6_4.

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Jan, S. y F. Baron. "32. Psychrotrophic heat-resistant bacteria in the sector of pasteurized liquid egg processing: a focus on the Bacillus cereus group". En Handbook of eggs in human function, 577–614. The Netherlands: Wageningen Academic Publishers, 2015. http://dx.doi.org/10.3920/978-90-8686-804-9_32.

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Stepaniak, L. "Psychrotrophic Bacteria | Other Psychrotrophs". En Encyclopedia of Dairy Sciences, 384–89. Elsevier, 2011. http://dx.doi.org/10.1016/b978-0-12-374407-4.00442-8.

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Stepaniak, L. "Psychrotrophic Bacteria: Other Psychrotrophs". En Reference Module in Food Science. Elsevier, 2021. http://dx.doi.org/10.1016/b978-0-12-818766-1.00384-6.

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McPhee, J. D. y M. W. Griffiths. "PSYCHROTROPHIC BACTERIA | Pseudomonas spp." En Encyclopedia of Dairy Sciences, 2340–45. Elsevier, 2002. http://dx.doi.org/10.1016/b0-12-227235-8/00405-3.

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Samaržija, Dubravka y Šimun Zamberlin. "Psychrotrophic Bacteria: Pseudomonas spp". En Reference Module in Food Science. Elsevier, 2020. http://dx.doi.org/10.1016/b978-0-08-100596-5.23045-x.

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Comi, G. y C. Cantoni. "PSYCHROTROPHIC BACTERIA | Arthrobacter spp." En Encyclopedia of Dairy Sciences, 372–78. Elsevier, 2011. http://dx.doi.org/10.1016/b978-0-12-374407-4.00440-4.

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McPhee, J. D. y M. W. Griffiths. "Psychrotrophic Bacteria | Pseudomonas spp." En Encyclopedia of Dairy Sciences, 379–83. Elsevier, 2011. http://dx.doi.org/10.1016/b978-0-12-374407-4.00441-6.

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Actas de conferencias sobre el tema "Psychrotrophic bacteria"

Maziero, João Pedro, Carolina Toledo Santos, Pricila Veiga dos Santos y Juliano Gonçalves Pereira. "Avaliação do uso de ozônio em temperaturas de leite cru refrigerado na contagem de psicrotróficos". En Semana Online Científica de Veterinária. CONGRESSE.ME, 2021. http://dx.doi.org/10.54265/gsri7118.

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A qualidade do leite cru está associada às boas práticas de ordenha proveniente de rebanhos sadios e com refrigeração obrigatória do leite cru na granja leiteira entre 4 e 7° C, podendo chegar até, no máximo, 9° C durante a coleta final (BRASIL 2018). Embora a refrigeração seja eficaz para aumentar a vida útil do leite cru, a manutenção das baixas temperaturas favorece a multiplicação de bactérias psicrotróficas, que produzem proteases e lipases termorresistentes, que permanecendo ativas mesmo após a pasteurização, podem afetar negativamente, tanto o próprio leite, quanto seus derivados (RIBEIRO et al., 2018). Visando reduzir a contagem de microrganismos psicrotróficos no leite cru, o presente trabalho avaliou a eficácia da aplicação de ozônio, considerado um bactericida verde por não ser poluente e não deixar resíduos no alimento, diretamente no tanque de resfriamento. As amostras de leite cru foram obtidas de um rebanho saudável e recolhidas diretamente do tanque de resfriamento da propriedade e armazenadas em frascos estéreis com volume de 6 litros sob refrigeração (4 e 9° C). A aplicação do ozônio seguiu delineamento fatorial com variáveis independentes sendo as temperaturas do leite (4 e 9° C) e os tempos de exposição ao ozônio (5 e 15 minutos) utilizando Gerador de Ozônio N202F Bivolt 500mg/h O³ Disinfector - Diluka Power. Foram retiradas amostras antes e após a ozonização. As amostras foram então armazenadas por 48 horas sob refrigeração (4° C) para permitir a proliferação da flora psicrotrófica. O teor de psicrotróficos e a contagem bacteriana total das amostras e do grupo controle foram avaliados em meio ágar bacteriológico PCA por 10 dias a 7° C e a 36° C por 24 horas, respectivamente. A aplicação de ozônio foi eficaz em reduzir a contagem de microrganismos psicrotróficos no tempo de 5 minutos a 4° C, esse resultado é extremamente satisfatório, visto que, a temperatura de aplicação é a mesma aplicada aos tanques de refrigeração nas propriedades, o que permitiria, facilmente, a aplicação nas próprias fazendas. Agradecimentos Agradecemos à equipe do Serviço de Orientação à Alimentação Pública da FMVZ-Unesp e ao proprietário da fazenda por disponilibizar o material utilizado na pesquisa. Referências BRASIL. Ministério da Agricultura, Pecuária e Abastecimento. Instrução normativa nº 76, de 26 de novembro de 2018. Regulamentos Técnicos que fixam a identidade e as características de qualidade que devem apresentar o leite cru refrigerado, o leite pasteurizado e o leite pasteurizado tipo A. Diário Oficial da União, Brasília, 2018. RIBEIRO JÚNIOR, J. C.et al. The main spoilage1 related psychrotrophic bacteria in refrigerated raw milk. Journal of dairy science, v. 101, n. 1, p. 75-83, 2018. PALAVRAS-CHAVE: Microbiologia dos alimentos, Qualidade do leite, Tecnologia verde

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