Relevant bibliographies by topics / Hydrolysis conditions

Academic literature on the topic 'Hydrolysis conditions'

Author: Grafiati
Published: 10 December 2022
Last updated: 19 February 2023

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Journal articles on the topic "Hydrolysis conditions"

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Thanh Ngoc, Nguyen Thi. "OPTIMIZATION FOR BATCH PROTEOLYTIC HYDROLYSIS OF SPENT BREWER’S YEAST BY USING PROTEASES." Vietnam Journal of Science and Technology 54, no. 4A (March 21, 2018): 181. http://dx.doi.org/10.15625/2525-2518/54/4a/11992.

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The yield of proteolylic hydrolysis for spent brewer’s yeast by protease and aminoacid contents of hydrolysates (the main factors influencing in taste of hydrolysed product) depends on factors influencing in catalytic activities of enzymes as temperature, pH value, type of used enzymes and ratio enzyme/substrate. With the purpose to hydrolyse the spent brewer’s yeast for food application, bitterness of hydrolysate takes the firth consideration, and than the yield of hydrolysing process plays economic role. In this paper, it is dealt with determination of optimal conditions to obtain the highest yield of hydrolysis process and the lowest bitterness of hydrolysate (the bitterness is determined by sensory evaluation, expressed equivalently with concentration of quinine). Response surface methodology (RSM) was used to determine optimum condition for batch proteolytic hydrolysis of spent brewer’s yeast. The influencing factors were investigated as temperature (X1): 40 oC–60 oC; pH (X2): 6.0–9.0, ratio E (flavourzyme)/S (X3): 5–10 U/g and hydrolysis time (X4): 6–9 hours. The experimental responses including degree of hydrolysis (Y1) (%) and bitterness of hydrolysate (Y2) (μmol quinine/ml) are performed in second-degree model. The optimal conditions for obtaining high degree of hydrolysis and low bitterness are determined: Ratio of enzyme mixture (alcalase 7.5 U/g and flavourzyme 8.5 U/g), pH 7.5, hydrolysis temperature at 52oC and hydrolysis time 9 hours. Under the optimal conditions, the actual values obtained for the yield of hydrolysis was 40.81 ± 0.044 % and the bitterness equivalently with concentration of quinine was 16.37 ± 0.03 μmol quinine/ml.
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Lisak Jakopović, Katarina, Seronei Chelulei Cheison, Ulrich Kulozik, and Rajka Božanić. "Comparison of selective hydrolysis of α-lactalbumin by acid Protease A and Protease M as alternative to pepsin: potential for β-lactoglobulin purification in whey proteins." Journal of Dairy Research 86, no. 1 (February 2019): 114–19. http://dx.doi.org/10.1017/s0022029919000086.

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AbstractThe experiments reported in this research paper examine the potential of digestion using acidic enzymes Protease A and Protease M to selectively hydrolyse α-lactalbumin (α-La) whilst leaving β-lactoglobulin (β-Lg) relatively intact. Both enzymes were compared with pepsin hydrolysis since its selectivity to different whey proteins is known. Analysis of the hydrolysis environment showed that the pH and temperature play a significant role in determining the best conditions for achievement of hydrolysis, irrespective of which enzyme was used. Whey protein isolate (WPI) was hydrolysed using pepsin, Acid Protease A and Protease M by randomized hydrolysis conditions. Reversed-phase high performance liquid chromatography was used to analyse residual proteins. Regarding enzyme selectivity under various milieu conditions, all three enzymes showed similarities in the reaction progress and their potential for β-Lg isolation.
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Egyed, J., and R. E. Oakey. "Hydrolysis of deoxycorticosterone-21-yl sulphate and dehydroepiandrosterone sulphate by microsomal preparations of human placentae: evidence for a common enzyme." Journal of Endocrinology 106, no. 3 (September 1985): 295–301. http://dx.doi.org/10.1677/joe.0.1060295.

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ABSTRACT The human placenta can hydrolyse both dehydroepiandrosterone-3β-yl sulphate (DHASO4−) and deoxycorticosterone-21-yl sulphate (DOCSO4−). There is some uncertainty as to whether the same or different enzymes are responsible for hydrolysis of these substrates. As a fresh approach to this problem we have compared the quantities of DHASO4− and DOCSO4− hydrolysed by microsomal preparations of placentae obtained from 14 normal pregnancies and from 14 pregnancies complicated by steroid sulphatase deficiency. Under the conditions used, and standardizing the results to unit time and quantity of protein, 1380–8830 fmol DHASO4− were hydrolysed by 14 normal placentae whereas < 1000 fmol DHASO4− were hydrolysed by the other 14 placentae, thereby designated as steroid sulphatase deficient. Net hydrolysis of DOCSO4− by the preparations of normal tissue was 9–52 fmol; hydrolysis of this substrate by steroid sulphatase-deficient tissues was indistinguishable from that by boiled tissue (< 29 fmol). Thus preparations of placentae which hydrolysed DHASO4− also hydrolysed DOCSO4− ; tissues which did not hydrolyse DHASO4− also failed to hydrolyse DOCSO4−. The quantities of DHASO4− and DOCSO4− hydrolysed by the 28 individual placentae showed a positive correlation (r = 0·91, P < 0·001). The apparent Michaelis constants for hydrolysis of DHASO4− and DOCSO4− were 38 and 274 μmol/l respectively. These results are consistent with the proposal that these substrates are hydrolysed by a common enzyme. J. Endocr. (1985) 106, 295–301
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CAMACHO, FERNANDO, PEDRO GONZÁLEZ-TELLO, MARÍA-PURIFICACIÓN PÁEZ-DUEÑAS, EMILIA-MARÍA GUADIX, and ANTONIO GUADIX. "Correlation of base consumption with the degree of hydrolysis in enzymic protein hydrolysis." Journal of Dairy Research 68, no. 2 (May 2001): 251–65. http://dx.doi.org/10.1017/s0022029901004824.

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It is fairly easy to control the enzymic hydrolysis of proteins in alkaline conditions by measuring the base consumption required to keep the pH constant in the reactor. Unfortunately, however, base consumption is not related in any simple way to the degree of hydrolysis reached at any given moment and to establish this relationship it is essential to find out the mean pK of the α-amino groups released during the hydrolytic process. We have shown here that the correct mean pK value varies according to the pH of the working conditions and that the relationship between these values may depend upon the kind of protein and protease used. We have put forward a method for determining this relationship experimentally by using a given protein–protease system, consisting of an alkaline titration of the raw protein and when partially hydrolysed. We have tested the results predicted by our theoretical model by applying it to the hydrolysis of whey proteins with a bacterial protease from Bacillus licheniformis at 50 °C, pH 8·0. This model can easily be applied to any hydrolytic process involving the appearance of functional groups that are partially protonizable under the working conditions in question in order to follow the kinetics of the reaction via the consumption of the neutralizing agent required to keep pH constant.
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Chatterjee, T., B. K. Chatterjee, and D. K. Bhattacharyya. "Study of lipase-catalyzed hydrolysis of some monoterpene esters." Canadian Journal of Microbiology 47, no. 5 (May 1, 2001): 397–403. http://dx.doi.org/10.1139/w01-026.

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Studies of the hydrolysis of bornyl, citronellyl, geranyl, and terpenyl acetates by commercially available lipases of Candida rugosa, Rhizopus arrhizus, and Mucor miehei are presented. The hydrolysis of these monoterpene esters is investigated at various temperatures and pHs, and the time dependence of the percentage of esters hydrolysed is studied. The catalytic activities of the lipases in hydrolysing the esters are compared and, overall, it is observed that under the experimental conditions used the nonspecific lipase from C. rugosa produces the highest yields of the monoterpene alcohols in comparison to the primary-ester specific lipases such as R. arrhizus and M. miehei. A rate kinetic model has been used to understand the time dependence of the yield of the product acid.Key words: enzymatic hydrolysis, kinetics, lipase, monoterpene esters.
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Jonsson, S., V. A. Vavilin, and B. H. Svensson. "Phthalate hydrolysis under landfill conditions." Water Science and Technology 53, no. 8 (April 1, 2006): 119–27. http://dx.doi.org/10.2166/wst.2006.242.

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Experimental data from a study using a landfill simulation reactor were used to develop and calibrate a one-dimensional distributed model of co-digestion of municipal solid waste and three phthalic acid diesters with different water solubilities. The three diesters were diethyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate. Two types of municipal solid wastes were assumed, easily degradable and recalcitrant. The model considered inhibition of hydrolysis of the recalcitrant fraction and phthalic acid esters, and also methanogenesis at acidic pH. The results indicated that the prolonged steady-state concentrations of the diesters in the leachates could be explained by equilibrium between physicochemical desorption and sorption processes for the three diesters. When methanogenic conditions were induced in the acidogenic landfill simulation reactor, inhibition of both hydrolysis of recalcitrant MSW and of phthalic acid esters ceased.
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Goel, Rajeev, Takashi Mino, Hiroyasu Satoh, and Tomonori Matsuo. "Comparison of hydrolytic enzyme systems in pure culture and activated sludge under different electron acceptor conditions." Water Science and Technology 37, no. 4-5 (February 1, 1998): 335–43. http://dx.doi.org/10.2166/wst.1998.0659.

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Enzymatic hydrolysis under different electron acceptor conditions in nutrient removal activated sludge treatment processes is a weak link in the Activated Sludge Model no. 2 (Henze et al., 1995). An experimental study was undertaken to gain insight into the hydrolysis process with specific focus on hydrolysis kinetics and rates under different electron acceptor conditions. Two pure cultures, Bacillus amyloliquefaciens (Gram positive) and Pseudomonas saccharophila (Gram negative) were chosen for the study. In addition, activated sludge grown in an anaerobic-aerobic system was tested for enzymatic activity using starch as the model substrate. The hydrolytic enzymes were found to be released into the bulk in pure cultures whereas the enzyme activity was found to be mainly associated with the cell surfaces in activated sludge. Further, it was observed that the development of the hydrolytic enzyme system in Bacillus amyloliquefaciens and P. saccharophila is strongly suppressed under anoxic and anaerobic conditions. However, the effect of anaerobic and aerobic incubation on hydrolytic enzyme activity in activated sludge was found to be small. Starch hydrolysis kinetic data from batch experiments with activated sludge followed substrate saturation kinetics that were linear with biomass concentration. Finally, the similar hydrolytic enzyme activities observed under anaerobic and aerobic phases of a sequencing batch reactor are explained by considering the aspects of enzyme location and enzyme system development under aerobic and anaerobic phases. It is proposed that the floc bound enzymes are recycled in a single sludge system so that an equilibrium exists between enzyme loss and synthesis at steady state.
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Kleekayai, Thanyaporn, Aurélien V. Le Gouic, Barbara Deracinois, Benoit Cudennec, and Richard J. FitzGerald. "In Vitro Characterisation of the Antioxidative Properties of Whey Protein Hydrolysates Generated under pH- and Non pH-Controlled Conditions." Foods 9, no. 5 (May 5, 2020): 582. http://dx.doi.org/10.3390/foods9050582.

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Bovine whey protein concentrate (WPC) was hydrolysed under pH-stat (ST) and non pH-controlled (free-fall, FF) conditions using Debitrase (DBT) and FlavorPro Whey (FPW). The resultant whey protein hydrolysates (WPHs) were assessed for the impact of hydrolysis conditions on the physicochemical and the in vitro antioxidant and intracellular reactive oxygen species (ROS) generation in oxidatively stressed HepG2 cells. Enzyme and hydrolysis condition dependent differences in the physicochemical properties of the hydrolysates were observed, however, the extent of hydrolysis was similar under ST and FF conditions. Significantly higher (p < 0.05) in vitro and cellular antioxidant activities were observed for the DBT compared to the FPW–WPHs. The WPHs generated under ST conditions displayed significantly higher (p < 0.05) oxygen radical absorbance capacity (ORAC) and Trolox equivalent antioxidant capacity (TEAC) values compared to the FF-WPHs. The impact of hydrolysis conditions was more pronounced in the in vitro compared to the cellular antioxidant assay. WPH peptide profiles (LC-MS/MS) were also enzyme and hydrolysis conditions dependent as illustrated in the case of β-lactoglobulin. Therefore, variation in the profiles of the peptides released may explain the observed differences in the antioxidant activity. Targeted generation of antioxidant hydrolysates needs to consider the hydrolysis conditions and the antioxidant assessment method employed.
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Thanh Ngoc, Nguyen Thi. "INFLUENCES OF TECHOLOGICAL HYDROLYSIS CONDITION ON NUCLEIC ACID CONTENT OF SPENT BREWER’S YEAST HYDROLYSATE." Vietnam Journal of Science and Technology 55, no. 5A (March 24, 2018): 169. http://dx.doi.org/10.15625/2525-2518/55/5a/12192.

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Currently, with the strong increasing of the brewing industry output, the consequencing amount of yeast residue is very large. Utilizing a large source of protein from brewers yeast to produce hydrolysed products using protease as food and food additives has a high real-life benefit. However, one limitation in the use of yeast and hydrolysis products is that the amount of nucleic acid in the yeast in particular and in the microbial cells is generally high. Nucleic acid is abundant in food that causes gout in humans and animals. There are many methods for reducing or separating nucleic acids in hydrolysed products such as extracellular ribonuclease enzymes, chemical agents, thermal shock and autolysis. Use extracellular ribonuclease enzyme for hydrolysis of nucleic acid gives good efficiency, but with high production cost. Chemical agents affect the quality of the hydrolysed products used in the food industry. There have been many good-efficiency studies using heat shock and autolysis to reduce the amount of nucleic acid in the hydrolysate. However, no research has been conducted to reduce the amount of nucleic acid by hydrolysis techniques. In this paper, we investigated the effects of heat shock, autolysis and hydrolysis techniques (batch, continuous overflow and continuous circulation) of brewery yeast protein to nucleic acid content in yeast hydrolysate. The results showed that the content of nucleic acid in the hydrolysate (with a concentration of 55 % dry matter) was the smallest. Under normal hydrolysis conditions, the nucleic acid content was 8.7 g / kg and when there was a heat shock+ autolysis, it decreased to 6.34 g/kg. After optimizing the hydrolysis conditions, the nucleic acid content of the hydrolysate was reduced to 5.41g/kg on continuous hydrolysis system.
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Margolis, Sam A., Lois Jassie, and H. M. Kingston. "The hydrolysis of proteins by microwave energy." Journal of Automatic Chemistry 13, no. 3 (1991): 93–95. http://dx.doi.org/10.1155/s1463924691000172.

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Microwave energy, at manually-adjusted, partial power settings has been used to hydrolyse bovine serum albumin at 125 °C. Hydrolysis was complete within 2 h, except for valine and isoleucine which were completely liberated within 4 h. The aminoacid destruction was less than that observed at similar hydrolysis conditions with other methods and complete hydrolysis was achieved more rapidly. These results provide a basis for automating the process of amino-acid hydrolysis.
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Dissertations / Theses on the topic "Hydrolysis conditions"

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Relvas, Frederico Miguel Horta de Albuquerque Moura. "Kinetic study of biomass hydrolysis under high pressure conditions." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13848.

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Mestrado em Engenharia Química
This study was focused on the kinetics of lignocellulosic biomass pre-treatment, in particular CO2-assisted autohydrolysis. The temperature was fixed at 180 ºC, varying pressure from 0 (CO2-free autohydrolysis), 20, 35 to 50 bar. For every pressure, a set of isothermal reactions was performed for various reaction times from 0 and 45 minutes. The pre-treatment resulted in a liquid, solid and gas phases, which were analyzed by HPLC. The liquid phase is essentially composed by sugars both in oligomer and monomer forms, mainly from xylan, also containing acetic acid and degradation products such as furfural and formic acid. In turn, there was an improvement of lignin and glucan’s fraction in the solid residue, being more pronounced for longer treatments. Regarding gas phase collected during depressurization, no traces of products from biomass hydrolysis were found. Basing on the literature and experimental results, 4 kinetic models were developed to predict the behavior of the biomass hydrolysis. Models for xylan, arabinoxylan, glucan and another for acetyl groups were presented. According to the results, the use of CO2 is beneficial for the selective fractionation of biomass, including hemicellulose and amorphous cellulose fractions. Beside, CO2 favors the production of xylooligosaccharides (XOS) achieving a maximum concentration of 14.76 g·L-1 at 50 bar assay vs 13.62 g·L-1 in case of autohydrolysis. Furthermore the conversion of oligomers to monomers is directly proportional to pressure and is enhanced by CO2 presence. With respect to the developed kinetic models, all showed good correlation with experimental data, with R2 as high as 0.9986. In the worst case, the R2 was 0.7865 what considering the so complex multistep analysis process can be acknowledge as a good result. Despite kinetic constants showed an increase of hydrolysis rate of xylan and arabinan in the presence of CO2, they decreases for higher pressures used. In turn, the model for acetyl groups also shows very consistent results with the lowest R2 of 0.9491. The removal of acetyl groups seems to be impaired by the carbon dioxide presence. With respect to glucan, the obtained data shows that reactions are close to zero order as they are independent on the products’ concentrations.
O presente trabalho focou-se no estudo cinético do pré-tratamento de biomassa lignocelulósica, em particular no processo de autohidrólise assistido com dióxido de carbono. O estudo foi feito fixando a temperatura em 180 ºC, variando a pressão entre 0 (ausência de CO2), 20, 35 e 50 bar. Para todas as gamas de pressão foram feitos ensaios isotérmicos entre 0 e 45 minutos. Os pré-tratamentos resultaram em 3 fases, líquida, sólida e gasosa, que foram analisadas por HPLC. A fase líquida é consituída essencialmente por açúcares (monómeros e oligómeros) provenientes maioritariamente do xilana, encontrando-se também ácido acético e produtos de degradação, tais como furfural e ácido fórmico. Por sua vez, as fracções de lignina e celulose na fase sólida aumentaram, sendo mais evidente para tratamentos mais longos. Em relação à fase gasosa, não foram encontrados quaisquer produtos de hidrólise da biomassa. Com base na literatura e nos resultados experimentais, foram desenvolvidos 4 modelos cinéticos para prever o comportamento da hidrólise da biomassa, correspondentes à fracção de xilana, arabinoxilana, celulose e grupos acetilo. De acordo com os resultados obtidos, concluiu-se que o uso de CO2 é útil para fraccionamento selectivo da biomassa, nomeadamente da fracção de hemicelulose e de celulose amorfa, apresentando também melhores resultados do que a autohidrólise na produção de xilooligossacarídeos (XOS), com um máximo de concentração de 14.76 g·L-1 para 50 bar vs. 13.62 g·L-1 na autohidrólise. Além disso, a conversão de oligomeros em monómeros é proporcional à pressão e favorecida pela presença de CO2. Quanto aos modelos cinéticos apresentam uma boa correlação com os dados experimentais, com um R2 mais alto de 0.9986. No pior caso, o R2 foi de 0.7865 que, tratando-se de uma reacção complexa, pode ser considerado um boa resultado. Apesar das constantes cinéticas mostrarem um aumento da hidrólise de xilana e arabinana na presença de CO2, estas decrescem em pressões mais elevadas. Por sua vez, os grupos acetilo também mostram resultados bastante consistentes, com o R2 mais baixo de 0.9491. A remoção de ácido acético parece ser prejudicada pela presença de CO2, enquanto os resultados da hidrólise de glucano sugerem uma cinética de ordem zero, uma vez que a concentração dos produtos aparenta ser independente da concentração dos diferentes produtos.
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Molwantwa, Jennifer Balatedi. "The hydrolysis of primary sewage sludge under biosulphidogenic conditions." Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1004020.

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The potential for using readily available and cost-effective complex carbon sources such as primary sewage sludge for a range of environmental remediation processes, including biological sulphate reduction, biological nutrient removal and the bioremediation of acid mine drainage, has been constrained by the slow rate of solubilization and low yield of soluble products, which drive the above mentioned processes. Previous work conducted by the Environmental Biotechnology Group at Rhodes University indicated that the degradation of primary sewage sludge was enhanced under sulphate reducing conditions. This was proven in both laboratory and pilot-scale (Reciprocating Sludge Bed Reactor) systems, where the particulate matter accumulated in the sludge bed and the molecules in smaller flocs were rapidly solubilized. The current study was aimed at investigating in more detail the factors that govern the enhanced hydrolysis under sulphate reducing conditions, and to develop a descriptive model to explain the underlying mechanism involved. The solubilization of primary sewage sludge under sulphate reducing conditions was conducted in controlled flask studies and previously reported findings of enhanced hydrolysis were confirmed. The maximum percentage solubilization obtained in this study was 31% and 63% for the methanogenic and sulphidogenic systems respectively, and this was achieved over a period of 10 days. A rate of reducing sugar production and complex molecule breakdown of 51 mg. L⁻¹.hr⁻¹ and 167 mg.L⁻¹.hr⁻¹ was observed for the methanogenic and sulphidogenic systems respectively. The flask studies revealed that during hydrolysis of primary sewage sludge under sulphidogenic conditions there was enhanced production of soluble products, specifically carbohydrates (reducing sugars) and volatile fatty acids, compared to methanogenic conditions. The rate at which these products were utilized was also found to be more rapid under sulphidogenic as compared to methanogenic conditions. A study of the distribution of volatile fatty acids indicated that acetate was utilized preferentially in the methanogenic system, and that propionate, butyrate and valerate accumulated with time. The converse was found to occur in the sulphidogenic system. The descriptive model developed from the results of this study was based on the fact that a consortium of bacteria, composed of hydrolytic, acidogenic and acetogenic species, carries out the solubilization of complex carbon sources. Furthermore, it is essential that equilibrium between product formation and utilization is maintained, and that accumulation of soluble end products impacts negatively on the rate of the hydrolysis step. It is therefore proposed that the relatively poor utilization of VFA and reducing sugars in the methanogenic system activates a negative feedback inhibition on the hydrolytic and/ or acidogenic step. This inhibition is reduced in the sulphidogenic system where the utilization of end products is higher.
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Awasume, Ignatius Ekwe, and Abel Prince Jabakumar Sathiyaraj. "Optimization of Pre-hydrolysis Conditions for the Production of Biogas." Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-16495.

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Hydrolysis and solubilisation of organic material is known to be the rate limiting step during anaerobic digestion. In this study, the effect of pre-hydrolysis was investigated. The substrate had a composition of the following wastes streams: fish and slaughterhouse waste, cleaning waste, doggy meat, doggy sludge, doggy dry food, mink (fur), Norway slurry, SOR2-Industrial waste, and municipal solid waste (MSW) from households in Borås community.Analyses were made on two batches of experiments performed at two different mesophilic temperature conditions; 34 0C and 42 0C and with or without the addition of mesophilic sludge obtained from a waste water treatment plant. One of the substrate maintained the original carbon/nitrogen (C/N) ratio, and for the other substrate the carbon nitrogen ratio was then slightly increased by adding 7.98g of special shredded paper which contains 82% volatile solids (VS). The experiments were run for 7days with samples collected regularly after 0 day, 4 days, 5 days, 6 days and 7 days retention time. Chemical oxygen demand (COD), pH, total nitrogen, and volatile fatty acids (VFAs) as process indicators were analyzed.The results showed that at 42 0C the rate of hydrolysis was faster with a higher COD release and removal. The optimum retention time for hydrolysis was 4 days and any longer time caused some of the carbon to be lost to carbon dioxide. The effect of adding mesophilic sludge had no significant effect. An increased C/N ratio resulted in a balanced system with lower VFAs produced compared with that from the original substrate mixture.

Acknowledgements: The authors are heartily thankful to their supervisor Ilona Sárvári Horváth whose guidance and support from the initial to the final level of this thesis work enabled us to gain a deeper understanding of the project.

We equally extend our sincere gratitude to the following persons who never ceased in helping until this work was complete.

Solmaz Aslanzadeh: For sharing her precious time and positive insight in coping with associated challenges of the project.

Hanson Jonas: Your assistance and patience over our laboratory experiments given the limited resources vis-a-vis students demand is quite reminding and saluted.

The support team at Sobacken Biogas plant: Your concern and timely assistance beginning from the supply of the substrate and the opportunity granted us to use your laboratory station greatly ensured results validation.

Program: MSc in Resource Recovery - Sustainable Engineering

Program: MSc in Resource Recovery - Industrial Biotechnology

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Ahuja, Nandita. "Impact of operating conditions on thermal hydrolysis pre-treated digestion return liquor." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/56647.

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Return liquor from thermal hydrolysis process (THP) can significantly add to the nitrogen load of a wastewater treatment plant (WWTP) and introduce UV quenching substances to the wastewater stream when recycled. While there are mature technologies in place to handle the inorganic nitrogen produced due to the thermal pretreatment, organic nitrogen remains a parameter of concern for utilities employing THP pretreatment. The impact of operating conditions of the THP on dissolved organic nitrogen (DON) and UV absorbance in return liquor was investigated. Operating conditions studied were (1) operating temperature (2) solids retention time (SRT) in the anaerobic digester (3) THP flash pressure (4) the effect of co-digestion of sewage sludge with food waste and, (5) polymer conditioning. Operating temperature and polymer dose had the most significant impact on DON and UV quenching. It was found that an increase in operating temperature resulted in an increase in DON, which was primarily contributed by the hydrophilic fraction. An increase in temperature also resulted in increased UV254 absorbance. However, this trend was not linear and the increase was more pronounced when the temperature was increased from 150 C to 170 C. Increasing flash pressure from 25 psi to 45 psi did not have a significant impact on the return liquor. However, increasing the flash pressure to 75 psi increased the DON and UV254 absorbing compounds. Co-digesting the sludge with food waste resulted in a slight increase in DON and a decrease in dissolved organic carbon (DOC) and UV quenching compounds. Increasing the SRT from 10 days to 15 days resulted in a slight decrease in DON but did not have any impact on UV254 absorbance. Overall, it can be concluded that optimizing operating conditions of thermal hydrolysis process can result in decreased DON and UV quenching compounds in the recycle stream.
Master of Science
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Mirshokraie, S. Ahmad (Seyed Ahmad). "Reactions of a-substituted non-phenolic lignin model compounds under alkaline hydrolysis conditions." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75783.

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Side-chain ether groups in lignin model compounds of the general structure 1-(3$ sp prime$,4$ sp prime$-dimethoxyphenyl)-1,2-diaryloxyethane exhibited hydrolytic cleavage (the extent depending on the substituents on the 1-aryloxy groups) in aqueous 2N NaOH at 150$ sp circ$C (i.e. under wood pulping conditions). The level of hydrolysis increased in phenylpropane models (i.e. with $ gamma$-CH$ sb2$OH). Thus the commonly accepted generalization that 1,2-diethers of 3$ sp prime$,4$ sp prime$-dimethyoxyphenylpropane are stable in hot alkali is valid only for 1-alkoxy compounds. The newly observed hydrolytic cleavage is influenced by a combination of steric effects, electronic effects and solubility parameters. These observations now make it possible to consider alkaline delignification in the light of gel-degradation theory.
A series of compounds of the general structure 1-(3$ sp prime$-4$ sp prime$,dimethoxyphenyl)-1-aryl-2-guaiacyloxyethane, where the 1-aryl group bore a hydroxy substituent, also exhibited alkaline hydrolysis, at 150$ sp circ$C, at the $ beta$-carbon. The extent was greater when the 1-aryl group bore an $o$-OH than when it bore a $p$-OH. Thus, the reaction was assisted by the nucleophilic attack of the $o$-phenoxide anion on the $ beta$-carbon.
A relatively high release of guaiacol occurred on treatment of 1-(3$ sp prime$,4$ sp prime$-dimethoxyphenyl)-1-thio-2-guaiacyloxyethane with 2N NaOH at 150$ sp circ$C, and the yield of guaiacol was increased when the terminal sidechain carbon bore a $-$CH$ sb2$OH group. Analogous $ alpha$-thioaryl and $ alpha$-thioalkyl compounds also exhibited greater ether cleavage than their oxy counterparts. The hydrolysis of the $ beta$-guaiacyl group was also enhanced by the presence of $ alpha$-seleno-containing groups.
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Henry, Lucile. "Étude et développement d'un procédé propre et innovant de traitement de la surface de fibres céramiques en conditions hydrothermales." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0328.

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Cette thèse s’inscrit dans une volonté d’adapter un procédé hydrothermal au traitement de la surface de fibres céramiques utilisées lors de la fabrication des composites à matrice céramique (CMCs). Le procédé conventionnel développé par la société Safran Ceramics se réalise en plusieurs étapes dont la principale consiste à dissoudre les phases oxydées de la surface des fibres Nicalon dans des bains d’acides. En conséquence, leurs propriétés chimiques de surface sont homogènes et un film de carbone microporeux est généré à la surface des fibres afin d’améliorer sa compatibilité chimique avec l’interphase de pyrocarbone qui y est déposée. Nous avons proposé de substituer ce procédé par un traitement par voie hydrothermale. En effet, l’eau possédant des propriétés physicochimiques ajustables en fonction des paramètres pression et température, il a été possible de modifier les propriétés de surface des fibres Nicalon d’une manière identique être productible au procédé conventionnel. L’efficacité et la compétitivité de ce traitement ont pu être démontrées par l’obtention de fibres avec des propriétés de surface optimales en une seule étape. Par la suite, l’étude du mécanisme réactionnel a révélé une attaque sélective des atomes de Si de la fibre selon des réactions d’hydrolyse. Puis, l’étude thermodynamique réalisée a mis en avant un régime à dominante cinétique. Finalement, les propriétés mécaniques des composites fabriqués à partir de tissus de fibres traités selon ce nouveau procédé ont été conformes aux objectifs. Ceci nous a donc permis de qualifier le traitement des fibres Nicalon par voie hydrothermale
This thesis project was carried out in order to develop a hydrothermal processfor the surface treatment of ceramic fibres which are integrated into the fabrication of ceramicmatrix composites (CMCs). A conventional process was developed by Safran Ceramics tomodify the surface chemistry of the Nicalon fibres following 3 steps. The main step consistsin dissolving the oxidised phases at the fibre surface by the use of strong acids. As aconsequence, the chemical homogeneity of the surface is enhanced and a microporouscarbon film is generated helping its compatibilization with the pyrocarbon interphase that isdeposited in between the fibres and the matrix. It was suggested to substitute thisconventional process by a hydrothermal treatment. Indeed, as water displays tunablephysico-chemical properties regarding the temperature and pressure conditions, it waspossible to recover fibres demonstrating reproducible and similar characteristics. Theefficiency and competitivity of the hydrothermal treatment have been assessed throughoptimised surface properties obtained after one single step. Next, the mechanisminvestigation revealed a selective attack of the Si atoms contained in the fibre via hydrolysisreactions. Then, the thermodynamic study pointed out the fact that the process wasdominated by a kinetic regim. Finally, the mechanical caracterisation of the CMCs made ofhydrothermal treated fibres showed results which met all the requirements. These finalobservations allowed us to complete the qualification of the hydrothermal process to treat thesurface of Nicalon fibres
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O'Neil, Joseph M. "Factors contributing to the degradation of poly(p-phenylene benzobisoxazole) (PBO) fibers under elevated temperature and humidity conditions." Thesis, Texas A&M University, 2006. http://hdl.handle.net/1969.1/4439.

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The moisture absorption behavior of Zylon fibers was characterized in various high temperature and high humidity conditions in a controlled environment. The results of these thermal cycling tests show that PBO fibers not only absorb, but also retain moisture (approximately 0.5-3%) when exposed to elevated temperature and humidity cycles. Also, the impurities of Zylon fibers were characterized through the use of Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and solid state Nuclear Magnetic Resonance (NMR). These tests demonstrated that, in addition to other impurities, PBO fibers may contain up to 0.55 weight percent phosphorus, and that this phosphorus is present in the form of phosphoric acid. It was also shown through accelerated hydrolytic degradation tests that production procedures used to neutralize the acid present in the fibers have a beneficial effect on the hydrolytic performance of the fiber. The data collected in this study was then compared and contrasted to known Kevlar studies, identifying similarities, differences, and potential trends. The results of these tests seem to indicate that there is accelerated acid catalyzed hydrolysis occurring in the fiber which is causing these fibers to degrade at an increased rate. This condition is further accelerated by heat and humidity induced permanent fiber swelling.
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Dong, Shuping. "Effects of acid hydrolysis conditions on cellulose nanocrystal yield and properties: A response surface methodology study." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/78102.

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Cellulose nanocrystals (CNCs) are frequently prepared by sulfuric acid hydrolysis of a purified cellulose starting material. CNC yields, however, are generally low, often below 20%. This study employs response surface methodology to optimize the hydrolysis conditions for maximum CNC yield. Two experimental designs were tested and compared: the central composite design (CCD) and the Box–Behnken design (BBD). The three factors for the experimental design were acid concentration, hydrolysis temperature, and hydrolysis time. The responses quantified were CNC yield, sulfate group density, ζ-potential, z-average diameter, and Peak 1 value. The CCD proved suboptimal for this purpose because of the extreme reaction conditions at some of its corners, specifically (1,1,1) and (–1,–1, –1). Both models predicted maximum CNC yields in excess of 65% at similar sulfuric acid concentrations (~59 wt %) and hydrolysis temperatures (~65 °C). With the BBD, the hydrolysis temperature for maximum yield lay slightly outside the design space. All three factors were statistically significant for CNC yield with the CCD, whereas with the BBD, the hydrolysis time in the range 60–150 min was statistically insignificant. With both designs, the sulfate group density was a linear function of the acid concentration and hydrolysis temperature and maximal at the highest acid concentration and hydrolysis temperature of the design space. Both designs showed the hydrolysis time to be statistically insignificant for the ζ-potential of CNCs and yielded potentially data-overfitting regression models. With the BBD, the acid concentration significantly affected both the z-average diameter and Peak 1 value of CNCs. However, whereas the z-average diameter was more strongly affected by the hydrolysis temperature than the hydrolysis time, the Peak 1 value was more strongly affected by the hydrolysis time. The CCD did not yield a valid regression model for the Peak 1 data and a potentially data-overfitting model for the z-average diameter data. A future optimization study should use the BBD but slightly higher hydrolysis temperatures and shorter hydrolysis times than used with the BBD in this study (45–65 °C and 60–150 min, respectively).
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Oyekola, Oluwaseun Oyekanmi. "The enzymology of sludge solubilisation under biosulphidogenic conditions : isolation, characterisation and partial purification of endoglucanases." Thesis, Rhodes University, 2004. http://hdl.handle.net/10962/d1003980.

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Endoglucanases play an important function in cellulose hydrolysis and catalyse the initial attack on the polymer by randomly hydrolysing the β-1,4 glucosidic bonds within the amorphous regions of cellulose chains. Cellulolytic bacteria have been isolated and characterised from the sewage sludge and the activation of several hydrolytic enzymes under biosulphidogenic conditions of sewage hydrolysis has been reported. The aims of this study were to: identify, induce production, locate and isolate, characterise (physicochemical and kinetic) and purify endoglucanases from anaerobic biosulphidogenic sludge. The endoglucanase activities were shown to be associated with the pellet particulate matter and exhibited a pH optimum of 6 and temperature optimum of 50 °C. The enzymes were thermally more stable when immobilised to the floc matrix of the sludge than when they were released into the aqueous solution via sonication. For both immobilised and released enzymes, sulphate was slightly inhibitory; activity was reduced to 84 % and 77.5 % of the initial activity at sulphate concentrations between 200 and 1000 mg/l, respectively. Sulphite was stimulatory to the immobilised enzymes between 200 and 1000 mg/l. Sulphide stimulated the activities of the immobilised endoglucanases, but inhibited activities of the soluble enzymes above 200 mg/l. The enzyme fraction did not hydrolyse avicel (a crystalline substrate), indicating the absence of any exocellulase activity. For CMC (carboxymethylcellulose) and HEC (hydroxylethylcellulose) the enzyme had K_m,app_ values of 4 and 5.1 mg/ml respectively and V_max,app_ values of 0.297 and 0.185 μmol/min/ml respectively. Divalent ions (Cu²⁺, Ni²⁺ and Zn²⁺) proved to be inhibitory while Fe²⁺, Mg²⁺ and Ca²⁺ stimulated the enzyme at concentrations between 200 and 1000 mg/l. All the volatile fatty acids studied (acetic acid, butyric acid, propionic acid and valeric acid) inhibited the enzymes, with acetic acid eliciting the highest degree of inhibition. Sonication released ~74.9 % of the total enzyme activities into solution and this was partially purified by PEG 20 000 concentration followed by DEAE-Cellulose ion exchange chromatography, which resulted in an appreciable purity as measured by the purification factor, 25.4 fold.
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Chassery, Aurélien. "Étude expérimentale et modélisation phénoménologique de l’hydrolyse de sodium tritié : influence des conditions opératoires sur la distribution du tritium dans les effluents." Phd thesis, Toulouse, INPT, 2014. http://oatao.univ-toulouse.fr/13934/1/chassery.pdf.

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L’hydrolyse contrôlée et progressive est une des solutions technologiques pour traiter le sodium tritié présent dans divers composants d’un Réacteur à Neutrons Rapides. Une étude expérimentale a été réalisée pour analyser et comprendre les phénomènes physico-chimiques mis en jeu lors de cette hydrolyse, fortement exothermique, et étudier l’influence des paramètres opératoires sur la répartition HT /HTO au sein de l’effluent liquide et de l’effluent gazeux générés. Les deux facteurs prédominants sont l’activité totale du sodium traité et le flux énergétique (J/s) dégagée par la réaction. Un modèle phénoménologique de l’hydrolyse de sodium tritié est proposé pour synthétiser les connaissances acquises et servir d’aide à la prédiction de la composition en tritium dans les effluents générés en vue de leur traitement.
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Books on the topic "Hydrolysis conditions"

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Canada, Atomic Energy of. Potentiometric and Laser Raman Study of the Hydrolysis of Uranyl Chloride Under Physiological Conditions and the Effect of Systematic and Random Errors on the Hydrolysis Constants. S.l: s.n, 1986.

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Book chapters on the topic "Hydrolysis conditions"

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Neureiter, Markus, Herbert Danner, Christiane Thomasser, Bamusi Saidi, and Rudolf Braun. "Dilute-Acid Hydrolysis of Sugarcane Bagasse at Varying Conditions." In Biotechnology for Fuels and Chemicals, 49–58. Totowa, NJ: Humana Press, 2002. http://dx.doi.org/10.1007/978-1-4612-0119-9_4.

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Wang, Kung-Tsung, and Shyh-Horng Chiou. "Peptide and protein hydrolysis by microwave irradiation: Kinetics and refinement of hydrolysis conditions for peptide-bond cleavage." In Amino Acids, 56–63. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-011-2262-7_7.

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Kim, Jun Seok, Y. Y. Lee, and Robert W. Torget. "Cellulose Hydrolysis Under Extremely Low Sulfuric Acid and High-Temperature Conditions." In Twenty-Second Symposium on Biotechnology for Fuels and Chemicals, 331–40. Totowa, NJ: Humana Press, 2001. http://dx.doi.org/10.1007/978-1-4612-0217-2_28.

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Ferrer, A., F. M. Byers, B. Sulbarán-De-Ferrer, B. E. Dale, and C. Aiello. "Optimizing Ammonia Processing Conditions to Enhance Susceptibility of Legumes to Fiber Hydrolysis." In Biotechnology for Fuels and Chemicals, 123–34. Totowa, NJ: Humana Press, 2002. http://dx.doi.org/10.1007/978-1-4612-0119-9_10.

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Ferrer, A., F. M. Byers, B. Sulbarán-de-Ferrer, B. E. Dale, and C. Aiello. "Optimizing Ammonia Processing Conditions to Enhance Susceptibility of Legumes to Fiber Hydrolysis." In Biotechnology for Fuels and Chemicals, 135–46. Totowa, NJ: Humana Press, 2002. http://dx.doi.org/10.1007/978-1-4612-0119-9_11.

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Ravallec-Ple, Rozenn, Laura Gilmartin, Alain Van Wormhoudt, and Yves Le Gak. "Influence of the Experimental Conditions on the Hydrolysis Process in Fish Hydrolysates." In Engineering and Manufacturing for Biotechnology, 51–58. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/0-306-46889-1_4.

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Du, Yang, and Junhua Chen. "Application of Handheld-Based Science Inquiry Experiment—Exploration of the Reaction Condition of Ferric Chloride Hydrolytic Action." In Lecture Notes in Electrical Engineering, 301–4. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-28744-2_37.

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"Hydrolytic Degradation." In Organic Chemistry of Drug Degradation, 16–47. The Royal Society of Chemistry, 2012. http://dx.doi.org/10.1039/bk9781849734219-00016.

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In this chapter, various hydrolytic mechanisms are discussed along with a number of factors that have an impact on the rate of hydrolysis, such as temperature, pH, steric hindrance, electronic properties of the substrate, and nature of the leaving group. The discussions are illustrated with approximately 50 examples of drugs containing various functional groups or moieties susceptible to hydrolytic degradation. These functional groups or moieties include ester, lactone, amide, β-lactam, carbamate, phosphates, phosphoramide, sulfonamide, imide, imine, acetal, hemiacetal, ether, and epoxide. The hydrolytic susceptibilities of these drugs are compared, whenever possible, by their hydrolysis activation energies in most cases. In cases where activation energies are not available in the literature, the enthalpy of activation and/or reaction rate constants are used for the comparison. Although such comparisons are of a semi-quantitative nature as the conditions for obtaining these kinetic parameters are not uniformly controlled, one can still get a good sense regarding the relative hydrolytic stability of the drugs discussed.
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Cheng, G., Y. Zhao, and C. Luo. "Experimental study on kitchen garbage hydrolysis conditions." In Energy, Environment and Green Building Materials, 199–202. CRC Press, 2015. http://dx.doi.org/10.1201/b18511-42.

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Tracey, M. R., R. P. Hsung, J. Antoline, K. C. M. Kurtz, L. Shen, B. W. Slafer, and Y. Zhang. "Hydrolysis of Imidazolium Chlorides under Basic Conditions." In Three Carbon-Heteroatom Bonds: Esters and Lactones; Peroxy Acids and R(CO)OX Compounds; R(CO)X, X=S, Se, Te, 1. Georg Thieme Verlag KG, 2005. http://dx.doi.org/10.1055/sos-sd-021-00345.

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Conference papers on the topic "Hydrolysis conditions"

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Wang, Hong-yan, Hong-hong Yi, Xiao-long Tang, Li-li Yu, Dan He, and Shun-zheng Zhao. "Effect of Preparation Conditions on Catalytic Hydrolysis of COS." In 2010 International Conference on Management and Service Science (MASS 2010). IEEE, 2010. http://dx.doi.org/10.1109/icmss.2010.5577157.

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Liu, M., J. Luo, and Y. Zeng. "Materials Corrosion in Hot Dilute Acidic Pre-Hydrolysis Biorefining Conditions." In MS&T19. TMS, 2019. http://dx.doi.org/10.7449/2019mst/2019/mst_2019_764_771.

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Liu, M., J. Luo, and Y. Zeng. "Materials Corrosion in Hot Dilute Acidic Pre-Hydrolysis Biorefining Conditions." In MS&T19. TMS, 2019. http://dx.doi.org/10.7449/2019/mst_2019_764_771.

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Groom, Taylor B., Michael P. Drolet, Jason Gabl, and Timothee L. Pourpoint. "Organic Acid–Promoted Hydrolysis of Ammonia Borane under Strained Conditions." In 2018 International Energy Conversion Engineering Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2018. http://dx.doi.org/10.2514/6.2018-4800.

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Dauknys, Regimantas, Aušra Mažeikienė, Anna Haluza, Illia Halauniou, and Victor Yushchenko. "Preliminary Investigation of Primary Sludge Hydrolysis." In Environmental Engineering. VGTU Technika, 2017. http://dx.doi.org/10.3846/enviro.2017.076.

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One of reasons of non-effective biological nutrient removal from wastewater is lack of readily biodegradable organic matter. This problem could be solved by application of sludge hydrolysis process. The conditions for hydrolysis of primary sludge could be created performing the recirculation of the primary sludge and ensuring the required sludge retention time. In the period of preliminary investigation, the following conditions were created in the primary sedimen-tation tank of Vitebsk WWTP: average sludge recirculation was 4.8 % of the inlet flowrate to the sedimentation tank and average SRT was 5 days. Obtained results showed that hydrolysis process allowed improving the ratio between organic matter and nutrients in wastewater.
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Ford, Sian, Katja Engel, Jeff Binns, Jennifer McKelvie, Josh Neufeld, and Gregory F. Slater. "Characterisation of the Rate of Phospholipid Hydrolysis Under Abiotic Conditions in Bentonite." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.726.

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Scott W Pryor and Nurun Nahar. "Impact of Dilute Acid Pretreatment Conditions and Enzyme System on Switchgrass Hydrolysis." In 2009 Reno, Nevada, June 21 - June 24, 2009. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2009. http://dx.doi.org/10.13031/2013.27175.

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"Optimization of ultrasound-assisted dilute acid hydrolysis conditions of tea processing waste." In 2016 ASABE International Meeting. American Society of Agricultural and Biological Engineers, 2016. http://dx.doi.org/10.13031/aim.20162456243.

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Germec, Mustafa, Kubra Tarhan, Ercan Yatmaz, Nedim Tetik, Mustafa Karhan, Ali Demirci, and Irfan Turhan. "Optimization of ultrasound-assisted dilute acid hydrolysis conditions of tea processing waste." In NABEC Papers. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2017. http://dx.doi.org/10.13031/nabec2017-009.

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Hochstetter, Gilles, and Patrick Dang. "Correlation Between Hydrolysis and the Ultimate Mechanical Properties of Polyamides in Offshore Conditions." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79976.

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Knowledge of mechanical properties of polymers used in the field of very technical applications is crucial for guaranteeing the safety of those applications. This is particularly true for pressure sheaths of offshore flexible pipes. For polyamide 11 (PA-11), which has been used for 30 years in the field of oil & gas applications, the decrease of its mechanical properties due to hydrolysis can be monitored by the decrease of the molecular weight, or Corrected Inherent Viscosity (CIV). According to API 17TR2 a design limit of CIV = 1.2 has been established for the use of PA-11 in dynamic applications. This design limit includes a safety factor, related to the kinetics of the molecular weight decrease of the PA-11, between CIV = 1.2 and the end of life criteria (CIV = 1.05). We show, in this paper, that this kinetic shall be established with tests enabling to precisely determine the near-equilibrium CIV value. This supposes sufficiently long-term ageing experiments at high temperatures. As a consequence, for any new polyamide, the time to reach the CIV of 1.2 can’t be considered as a sufficient design factor. Moreover, the safety factor for a new polyamide should be carefully estimated. Therefore, the complete characterization of the mechanical behaviour should be done in relation with the ageing time and temperature. Only at this condition, one can expect to be able to establish a new and correct end of life criterion for a new polyamide based on mechanics. In a second time, this criterion could be linked to some physico-chemical parameters. We point out that the maximum elongation evolution of the material with the molecular weight couldn’t be considered as sufficiently precise to conclude about the mechanical resistance of the aged material for flexible pipe application. We thus present in this paper a new mechanical protocol.
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Reports on the topic "Hydrolysis conditions"

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Lers, Amnon, and Pamela J. Green. LX Senescence-Induced Ribonuclease in Tomato: Function and Regulation. United States Department of Agriculture, September 2003. http://dx.doi.org/10.32747/2003.7586455.bard.

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Natural leaf senescence, which occurs even when growth conditions are near optimal, has a negative influence on yield. Postharvest induced senescence contributes to the losses of quality in flowers, foliage, and vegetables. Strategies designed to control the senescence process in crop plants could therefore have great applied significance. However, the successful design of such strategies requires a better insight into the senescence machinery and control in higher plants. A main feature of senescence is the hydrolysis of macromolecules by hydrolases of various types such as ribonucleases (RNases) and proteases. Previously we had identified and characterized the tomato LX RNase gene demonstrating its transcript to be highly and specifically induced during senescence. This reported study was focused on LX but also had broadened our research to other senescence-associated nucleic acids degrading enzymes to learn about their function and the regulation of their encoding genes. Beside tomato we used parsley and Arabidopsis for the study of: the bi-functional nuclease which has a role in senescence. The study of different senescence- associated nucleases in few plant systems will allow a more general view on function and regulation of these enzymes in senescence. The specific original proposed objectives included: 1. Study the consequences of alterations in LX RNase level on tomato leaf senescence and general development; 2. Analyze stimuli which may participate in senescence-specific activation of the LX gene; 3. Clone the senescence-associated BFNI nuclease gene homologue from tomato. 4. Further characterize the sequences required for senescence-specific gene expression. Homozygous transgenic plants in which LX gene was either inhibited or over-expressed were generated. In both of these LX mutated plants no major phenotypic consequences were observed, which may suggests that LX is not essential for plant growth under optimal growth conditions. Lack of any abnormalities in the LX over-expressing lines suggests that special system exist to allow function of the RNase only when needed. Detailed analyses of growth under stress and consequences to RNA metabolism are underway. We have analyzed LX expression on the protein level demonstrating that it is involved also in petal senescing. Our results suggest that LX is responding to complex regulation involving developmental, organ dependent factors and responds differently to hormonal or environmental stimuli in the different plant organs. The cloned 1.4 kb promoter was cloned and its analysis revealed that probably not all required elements for senescence induction are included. Biochemical analysis of senescence-associated be-functional nucleases in the different plants, tomato, parsley and Arabidopsis, suggests they belong to a sub-class within the type I plant nucleases. The parsley PcNUC1/2 nuclease protein was purified from senescing leaves its and activity was studied in vitro revealing endo-, double strand, nucleolytic activity and exo-nucleolytic activity. Its encoding gene was cloned and found to be induced on the mRNA level. The promoter of the related Arabidopsis BFNI nuclease was shown in both tomato and Arabidopsis to be able and direct senescence-specific expression suggesting that, at least part, the gene is regulated on the transcriptional level and that the mechanism for this senescence-specific regulation is conserved between different plants. Few plants in which the BFNI gene is mutated were identified which are subjected now to detailed analysis. Our results suggest that the senescence-related nucleic acid degrading enzymes share similarities in both function and regulation between different plants and possibly have important functions in processes un-related to senescence. Still, the function of these enzymes, at least in some cases is not essential to plant development under optimal growth conditions. We are now at the stage which permits in depth investigation of the specific functions and mode of molecular regulation of senescence-associated nucleases with the aid of the research tools developed. The isolated senescence-specific promoter, shown to be active in heterologous plant system, could be utilized in agricultural-related biotechnological applications for retardation of senescence.
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Lers, Amnon, E. Lomaniec, S. Burd, A. Khalchitski, L. Canetti, and Pamela J. Green. Analysis of Senescence Inducible Ribonuclease in Tomato: Gene Regulation and Function. United States Department of Agriculture, February 2000. http://dx.doi.org/10.32747/2000.7570563.bard.

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Natural leaf senescence has a negative influence on yield. Postharvest induced senescence contributes to the losses of quality in flowers, foliage, and vegetables. Strategies designed to control the senescence process in crop plants could therefore have great applied significance. Senescence is regulated by differential gene expression yet, functional characterization of the genes specifically induced and study of their expression control, is still in its infancy. Study of senescence-specific genes is required to allow identification of regulatory elements participating in senescence-induced expression and thus provide insights into the genetic regulation of senescence. A main feature of senescence is the hydrolysis of macromolecules by hydrolases of various types such as RNases and proteases. This study was aimed a analysis of senescence-inducible RNases in tomato with the following objectives: Isolation of senescence-inducible RNase cDNA clones; Expression analyses of RNase genes during senescence; Identification of sequences required for senescence-induced gene expression; Functional analyses of senescence-inducible RNases. We narrowed our aims somewhat to focus on the first three objectives because the budget we were awarded was reduced from that requested. We have expanded our research for identification senescence-related RNase/nuclease activities as we thought it will direct us to new RNase/nuclease genes. We have also carried out research in Arabidopsis and parsley, which enabled us to draw mire general conclusions. We completed the first and second objectives and have made considerable progress on the remaining two. We have defined growth conditions suitable for this research and defined the physiological and biochemical parameters characteristic to the advance of leaf senescence. In tomato and arabidopsis we have focused on natural leaf senescence. Parsley was used mainly for study of postharvest senescence in detached leaves. We have identified a 41-kD a tomato nuclease, LeNUCI, specifically induced during senescence which can degrade both RNA and DNA. This activity could be induced by ethylene in young leaves and was subjected to detailed analysis, which enabled its classification as Nuclease I enzyme. LeNUCI may be involved in nucleic acid metabolism during tomato leaf senescence. In parsley senescing leaves we identified 2 main senescence-related nuclease activities of 41 and 39-kDa. These activities were induced in both naturally or artificially senescing leaves, could degrade both DNA and RNA and were very similar in their characteristics to the LeNUCI. Two senescence-induced RNase cDNAs were cloned from tomato. One RNase cDNA was identical to the tomato LX RNase while the second corresponded to the LE RNase. Both were demonstrated before to be induced following phosphate starvation of tomato cell culture but nothing was known about their expression or function in plants. LX gene expression was much more senescence specific and ethylene could activate it in detached young leaves. LE gene expression, which could be transiently induced by wounding, appeared to be activated by abscisic acid. We suggest that the LX RNase has a role in RNA catabolism in the final stage of senescence, and LE may be a defense-related protein. Transgenic plants were generated for altering LX gene expression. No major visible alterations in the phenotype were observed so far. Detailed analysis of senescence in these plants is performed currently. The LX promoter was cloned and its analysis is performed currently for identification of senescence-specific regulatory elements. In Arabidopsis we have identified and characterized a senescence-associated nuclease 1 gene, BFN1, which is highly expressed during leaf and stem senescence. BFN1, is the first example of a senescence- associated gene encoding a nuclease I enzyme as well as the first nuclease I cloned and characterized from Arabidopsis. Our progress should provide excellent tools for the continued analysis of regulation and function of senescence-inducible ribonucleases and nucleases in plants. The cloned genes can be used in reverse genetic approaches, already initiated, which can yield a more direct evidence for the function of these enzymes. Another contribution of this research will be in respect to the molecular mechanism, which controls senescence. We had already initiated in this project and will continue to identify and characterize regulatory elements involved in senescence-specific expression of the genes isolated in this work.
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