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1
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.
2
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
Full Text
3
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.
5
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.
Master of Science
6
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.
7
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
8
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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Previous issue date: 2006-03-16Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
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.
9
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
10
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
11
Drevet, Pascal. "Etude du système protéolytique intracellulaire d'une bactérie psychrotrophe du genre Arthrobacter". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376046391.
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Michel, Valérie. "Caracterisation de la reponse aux chocs thermiques d'une bacterie psychrotrophe d'alteration, pseudomonas fragi". Clermont-Ferrand 2, 1996. http://www.theses.fr/1996CLF21813.
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Les effets de chocs thermiques sur la croissance et la synthese proteique ont ete etudies chez pseudomonas fragi, bacterie psychotrophe d'alteration des aliments. Les cinetiques de synthese proteique ont ete caracterisees par autoradiographies des proteines intracellulaires marquees a la methionine-#3#5s et separees en electrophorese bidimensionnelle (e-2d). La croissance se poursuivait avec un taux caracteristique de la temperature finale du choc de facon immediate apres les chocs chauds de 5 a 20 ou 30c et de 28 a 34c, et apres 3 et 5 h de latence a la suite d'un transfert de 20 a 5c et de 30 a 5c. Les profils obtenus en e-2d apres les differents chocs ont revele des variations dans le niveau relatif de synthese de 20 a 37 proteines. Ces proteines ont ete repertoriees en fonction de leur poids moleculaire, point isoelectrique et de leur cinetique de variations en reponse a un choc thermique. Les principales proteines impliquees dans la reponse adaptative de p. Fragi a la temperature, ont ainsi ete caracterisees. Les genes de 3 d'entre elles, designees c7. 0, c8. 0, e7. 0, ont ete amplifies pas pcr et sequences. Ces proteines appartiennent a une famille d'activateur de faible masse moleculaire capables de se lier aux acides nucleiques dont le representant type est cspa, la proteine majeure de choc froid d'e. Coli, caracterisee comme un activateur transcriptionnel
13
Dai, Xian-zhu. "Studies on the folding of an outer membrane protein from a psychrotrophic bacterium, Shewanella livingstonensis Ac10". Kyoto University, 2012. http://hdl.handle.net/2433/157718.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第16927号
農博第1943号
新制||農||1001(附属図書館)
学位論文||H24||N4688(農学部図書室)
29602
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 小川 順, 教授 阪井 康能
学位規則第4条第1項該当
14
GRABSKA, JADWIGA. "Contribution a la determination de l'activite des lipases des bacteries psychrotrophes dans le lait cru". Paris, Institut national d'agronomie de Paris Grignon, 1986. http://www.theses.fr/1986INAPA003.
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Le principal objectif etait la recherche et la mise au point d'une methode de determination de l'activite lipasique des laits de collecte permettant de differencier la lipoproteine lipase naturelle et les lipases excretees par les bacteries psychrotrophes, notamment le genre pseudomonas. Ces toutes dernieres annees, plusieurs methodes ont ete proposees dans le but de detecter ces enzymes, le plus souvent presentes en faibles quantites en raison de leur thermoresistance. La complexite du milieu lait, avec la presence de proteines, de matieres grasses et celles d'une autre enzyme lipolytique, rend le probleme difficile. Une methode immunologique pour le dosage des lipases represente une solution particulierement interessante etant donne l'expansion que connaissent actuellement ces methodes
15
Girardot, Françoise. "Bases moléculaires de la croissance à basse température chez la bactérie psychrotrophe Arthrobacter globiformis SI55". Lyon 1, 1995. http://www.theses.fr/1995LYO10164.
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La croissance a basse temperature a ete etudiee chez la bacterie psychrotrophe arthrobacter globiformis si55. Elle fait intervenir des proteines particulieres appelees caps (cold acclimation proteins) qui persistent pendant toute la duree de la croissance au froid. D'autres proteines appelees csps (cold shock proteins) sont surexprimees transitoirement apres des chocs froids d'amplitude variee. L'analyse en afc (analyse factorielle des correspondances) de leur cinetique d'induction en fonction de la temperature de choc a permis de degager nettement trois groupes de proteines: un groupe de proteines specifiquement induites apres un choc froid de 25 a 4c, un groupe de proteines induites apres des chocs froids d'amplitude moyenne et un troisieme groupe de proteines presentes lors de tous les chocs thermiques etudies. L'implication des proteines de choc froid dans l'adaptation a la croissance aux bases temperatures a ete montree. Un gene appele cspagl codant pour une proteine de 67 acides amines et presentant 64% d'identite avec la proteine cs7,4, a ete clone et sequence. La proteine correspondante a ete identifiee comme etant la csp/cap a9. Elle est surexprimee par a. Globiformis dans l'heure qui suit un choc froid de 25 a 4c et persiste dans les cellules en croissance a 4c. Le blocage de la synthese des csps et caps empeche la reprise de la croissance apres un choc froid. La reponse au choc hypothermique apparait etre une reponse adaptative. De plus, la proteine cspagl est impliquee dans la reprise de la croissance apres un choc froid de 25 a 4c. Parmi les caps mises en evidence a 4c, se trouve une proteine de poids moleculaire similaire a la proteine h-ns et qui presente des epitopes communs avec elle
16
Trial, De Greef Nathalie. "Etude de l'effet de l'hydrolyse des caséines par des protéases de bacteries psychrotrophes sur la texture du yoghourt brassé". Montpellier 2, 2002. http://www.theses.fr/2002MON20001.
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Sugiura, Miwa. "Effects of eicosapentaenoic acid-containing phospholipids on the formation of membrane proteins from Shewanella livingstonensis Ac10". Kyoto University, 2018. http://hdl.handle.net/2433/235099.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第21379号
農博第2303号
新制||農||1071(附属図書館)
学位論文||H30||N5152(農学部図書室)
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 植田 充美, 教授 小川 順
学位規則第4条第1項該当
18
Felipus, Nadine Cristina. "Impacto do transporte a granel na qualidade microbiológica e físico-química e na composição do leite cru refrigerado em indústria de laticínios". Universidade do Estado de Santa Catarina, 2017. http://tede.udesc.br/handle/handle/2562.
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Milk is nutritionally complete, but a highly perishable food and its characteristics easily altered by the action of microorganisms and by the manipulation to which it is submitted. The quality and shelf life of the product that reaches the consumer is directly related to the raw material received for industrialization, and consequently to the conditions and practices carried out in obtaining, storing and transporting. The objective of this study was to evaluate the influence of transport of raw milk on the count of psychrotrophic microrganisms, total bacterial count, physical-chemical and compositional analyses of the refrigerated raw milk received in a dairy industry of Vale do Itajaí – SC, Brazil. Other objective of this study was to evaluate the use of the preservative azidiol ®, under controlled conditions and under field conditions, in the count of psychrotrophic microorganisms and in the total bacterial count of refrigerated raw milk. Two experiments were carried out. In the first one, samples were collected, with and without the use of the preservative azidiol®, in bulk tanks of 3 dairy farms, which were stored under laboratory refrigeration (7ºC) and analyzed at pre-defined times (0, 6, 12 and 24 hours). In the second experiment, samples were collected with and without the use of the azidiol® preservative in the raw milk capture at routes of a dairy (in the storage tanks of the farms, in the isothermal compartments of the trucks and in the storage silo of the industry), doing analysis at varying times. Data were analyzed by ANOVA, regression analysis, means comparison and multivariate factorial analysis. Samples collected without preservatives showed increasing psychrotrophic microrganisms counts and total bacterial count as the time between collection and analysis increased. In the samples conserved by azidiol ®, psychrotrophic microrganisms counts and total bacterial count remained constant during the time between collection and analysis. The transport of raw milk in bulk worsened the microbiological quality of the milk, but did not show influence on the compositional and physical-chemical results of the milk received in the industry. Poor hygiene conditions in storage rooms and in expansion tanks influenced the increase of psychrotrophic microrganisms counts and total bacterial count. This increase was also related to farms with lower production, but with less representative influence. It was observed a relation of milk transport in bulk in cleaner trucks with lower counts of psychrotrophic microorganisms. The transport route time and temperature increase during the transport increased counts of total bacteria and psychrotrophic bacteria, with more pronounced effect for total bacterial count
O leite é um alimento nutricionalmente completo, porém altamente perecível, tendo suas características facilmente alteradas pela ação de microrganismos e pela manipulação a que é submetido. A qualidade e tempo de prateleira do produto que chega ao consumidor estão diretamente relacionados à matéria-prima recebida para industrialização e, consequentemente, às condições e práticas realizadas na obtenção, armazenamento e seu transporte. Este estudo teve como objetivo a avaliação da influência do transporte do leite cru a granel sobre a contagem de microrganismos psicrotróficos, contagem bacteriana total, análises físico-químicas e composição do leite cru refrigerado recebido em uma indústria de laticínios da Região do Vale do Itajaí – SC. Também objetivou avaliar o uso do conservante azidiol®, em condições controladas e em condições a campo, na contagem de microrganismos psicrotróficos e na contagem bacteriana total de leite cru refrigerado. Foram realizados dois experimentos. No primeiro, foram coletadas amostras, com e sem o uso do conservante azidiol®, em tanques de expansão de três propriedades rurais, as quais foram armazenadas em laboratório e sob refrigeração (7ºC) e analisadas em tempos pré-definidos (0, 6, 12 e 24 horas). No segundo experimento foram coletadas amostras com e sem a adição do agente bacteriostático azidiol® em rotas de captação de matéria-prima de um laticínio (nos tanques de armazenamento das propriedades rurais, nos compartimentos isotérmicos dos caminhões e no silo de armazenamento da indústria), analisando-as em tempos variáveis. Os dados foram avaliados por análise de variância e de regressão, comparação de médias e pela técnica de análise multivariada fatorial. Amostras coletadas sem conservante demonstraram contagem de microrganismos psicrotróficos e CBT crescentes à medida que o tempo entre a coleta e a análise aumentava. Já nas amostras adicionadas do conservante azidiol® a contagem de microrganismos psicrotróficos e a CBT se mantiveram constantes durante o tempo entre a coleta e a análise. O transporte do leite cru a granel piorou a qualidade microbiológica do leite; porém, não demonstrou influência nos resultados das análises composicionais e físico-químicas do leite recebido na indústria. Condições ruins de higiene nas salas de armazenamento e nos tanques expansão influenciaram o aumento da contagem de microrganismos psicrotróficos e a CBT. Este aumento também foi relacionado com propriedades com menor produção de leite, porém, com influência menos representativa. Observou-se relação do transporte do leite a granel em caminhões mais limpos com menores contagens de microrganismos psicrotróficos. Maior tempo da rota de transporte e o aumento da temperatura do leite durante o transporte aumentaram as contagens de bactérias totais e de microrganismos psicrotróficos, sendo este efeito mais pronunciado para a CBT
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Reche, Natália Luiza Machado. "Influência do armazenamento do leite em resfriador por expansão direta sobre a contagem de micro-organismos e estabilidade da caseína". Universidade do Estado de Santa Catarina, 2013. http://tede.udesc.br/handle/handle/900.
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Previous issue date: 2013-11-28The milk is rich in proteins, lipids, water and carbohydrates, making it an excellent environment for bacterial contamination from different origins and for its proliferation. Bacterial multiplication depends on its capacity of adaptation to the environment and time available. In dairy farms, milk can be storage under cold in bulk tanks models of two and four milking capacity, with a chilling capacity of 50% and 25% respectively of its total volume, in each milking process. The use of cold storage in milk production reduced the occurrence of acid milk, however, increased the proliferation of psychrotrophic microorganisms. These microorganisms presents proteolytic capacity over casein without modifing the milk acidity. This proteolytic capacity could be responsible for unstable non-acid milk (UNAM). The purpose of this study was to evaluate the effect of the cold storage length of time and temperature of raw milk in bulk tanks of two and four milking models on psychrotrophic bacterial count (PBC), casein stability in alcohol test and occurrence of UNAM. The study was conducted in 19 dairy farms in two rehearsal and each farm had a direct expansion bulk milk tank of two or four milking models. Dairy farms with an interval of four milking between milk transportation to the processing industry were selected, thus the milk had a 36 hours of cold storage in the dairy farm. Samples were collected before and after each milking for bacterial total count (BTC), physical-chemical analysis and PBC. Samples of 12 from a total of 19 dairy farms were collected for casein quantification. The length of time of cold storage did not affect the BTC and PBC (P > 0,05). The bulk tank model only affected the PBC (P < 0,05), presenting a lower mean tank s model of two milking when compared with models of four milking (3,61±0,104 and 4,00±0,120 CFU/mL(log10)). The PBC did not affected the casein fractions, however the length of time of cold storage affected the қ and β casein fraction concentrations. The reductions in these casein fractions did not affect the casein stability in the alcohol test. The length of time of cold storage affected the casein stability (P < 0,05) in the alcohol test without affecting the UNAM occurrence. Bulk tanks, when used properly in concern of raw milk volume to be chilled, allow the BTC and PBC rates to remain stable. The length of time of cold storage does not affect BTC and PBC but affects the casein concentration and casein stability in the alcohol test without affecting the UNAM occurrence
O leite é um meio nutritivo facilmente colonizado por bactérias de diferentes origens, com taxa de proliferação condicionada à capacidade do micro-organismo adaptar-se ao ambiente e do tempo disponível. Na propriedade rural o leite pode ser armazenado por até 48 horas em tanques de expansão direta modelo de duas ou quatro ordenhas, os quais diferem na capacidade de resfriamento a cada ordenha, respectivamente, esses equipamentos são capazes de resfriarem 50% e 25% de seu volume a cada ordenha. A conservação do leite sob resfriamento pode não ser suficiente para o controle de micro-organismos psicrotróficos, os quais apresentam atividade proteolítica sobre a caseína sem alterar a acidez do leite, podendo ser um fator desencadeador do leite instável não ácido (LINA). O objetivo do presente estudo foi avaliar o efeito do tempo e temperatura de estocagem do leite cru em tanques de expansão direta modelos de duas e quatro ordenhas sobre a contagem bacteriana total (CBT) e contagem de bactérias psicrotróficas (CBP), assim como, determinar o efeito do tempo e da CBP sobre a estabilidade da caseína ao teste do álcool e a ocorrência de LINA. O experimento foi conduzido em 19 propriedades leiteiras localizadas nas regiões Serrana e Meio-oeste Catarinense, as quais possuíam equipamentos de refrigeração do leite por expansão direta modelo duas ou quatro ordenhas com taxa de ocupação de no mínimo 60%. Nas propriedades rurais foram avaliadas informações referentes ao intervalo de 36 horas entre a captação de leite a granel para a indústria de laticínios, as quais incluíam monitoramento temperatura leite, temperatura ambiente e umidade relativa do ar, aplicação de questionários aos responsáveis pela ordenha e coletas de amostras de leite antes e após a cada ordenha para análise de CBT, CBP, composição e teste físico-químicos (pH, acidez titulável e concentração alcoólica), sendo que em 12 das propriedades as frações de caseína foram quantificadas em duplicata. O tempo de estocagem do leite cru não afetou a CBT e CBP (P > 0,05). O modelo de tanque de expansão afetou somente a CBP (P < 0,05), com média inferior para amostras de leite de tanques de duas ordenhas em relação a quatro ordenhas (3,61±0,104 e 4,00±0,120 UFC/mL(log10)). A CBP não afetou as frações das caseínas e caseína total, entretanto, o tempo de estocagem do leite cru reduziu (P < 0,05) a concentração das frações қ e β da caseína e caseína total. A redução das frações de caseína não demonstrou efeito sobre a estabilidade do leite ao teste do álcool. O tempo de estocagem reduziu a (P < 0,05) a estabilidade do leite ao teste do álcool, entretanto não cursou com o aumentou a ocorrência de LINA. Conclui-se que tanques de resfriamento por expansão, utilizados dentro de suas especificações quanto ao volume de leite a ser resfriado, permitem a manutenção da CBT e CBP . O tempo de estocagem não afeta a CBT e CBP, entretanto reduz a concentração de caseína e a estabilidade do leite ao teste do álcool, sem alterar a ocorrência de LINA
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Liu, Chin-Chun y 劉芹君. "Isolation of Psychrotrophic Bacteria in the Coastal Area of Shalun, Tamshui". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/13844082927179602188.
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碩士國立陽明大學
微生物暨免疫學研究所
88
In this thesis, we sampled seawater and sediment at the seaside of northern Taiwan and studied several novel microbial strains isolated from the sample. Among all isolates, seven pure strains were picked for further study, and they are designated as strains SR1~SR7 respectively. By using various classification methods, such as morphology, physiological properties, biochemical tests, GC content, and 16S rRNA sequence comparison, strains SR1~SR7 are classified into known categories. Strains SR1~SR7 are all Gram-negative, motile, polar-flagellated, aerobic, rod-shaped eubacteria and can grow in nutrient media containing 0.5%~12% of NaCl. Sodium ion is essential for growth. Strains SR1~SR7 are psychrotrophs and able to grow at 4 oC with optimal growth at 20~25 oC. They are neutrophilic and cannot ferment glucose in the Hugh-Leifson test. All of them are oxidase-positive and catalase-positive. They can produce caseinase and lipase, but not agarase, chitinase, and urease. Some strains of them are able to hydrolyze starch and gelatin. Strains SR1~SR7 cannot reduce nitrate, and their G+C contents of the chromosome DNA are 43%、46%、43~44%、41~42%、46%、48%、47% respectively. The 16S rRNA sequences of our strains are similar to Pseudoalteromonas spp.. Phenotypes of our strains are also close to that of Pseudoalteromonas spp.. Consequently, we propose that strains SR1~SR7 belong to genus Pseudoalteromonas. They are probably new species in the genus Pseudoalteromonas.
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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". Thesis, 1987. http://hdl.handle.net/1957/27089.
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Heat resistant sporeforming psychrotrophic bacteria were
isolated from raw milk samples from 59 Grade A farms in Oregon.
Forty-nine of the 59 (83%) raw milk samples in this survey
contained sporeforming psychrotrophic bacteria; isolates from
twenty-four (40%) of the samples exhibited proteolytic properties. Populations of sporeforming psychrotrophic bacteria ranged
from <10 to >10,000 CFU/mL for all samples. One hundred-two
isolates were identified as Bacillus species. Twelve different
Bacillus species were identified with B. licheniformis being the
most predominate (18% of the samples) and B. laterosporus the
least frequently isolated species, (2%). Fifty-eight percent of
the bacilli isolates produced a bitter off-flavor and putrid
odor, while 42% produced a fruity and/or rancid off-flavor when
inoculated into sterile whole milk. Based on biochemical
activity tests, 83% of the thermoduric isolates hydrolysed
casein while 56% were proteolytic (in litmus milk), 57% demonstrated
lipolytic activity and 31% produced acid in litmus milk. Forty-eight isolates that tested positive for proteolysis were
evaluated quantitatively for activity, which ranged from 0.93 to
1.93 units (expressed as mM of alanine). Isolates of Bacillus
cereus var. mycoides demonstrated significantly higher
(p>0.05) proteolytic activity than other Bacillus species
isolated.Graduation date: 1988
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Sun, Jun-Ning y 孫君寧. "The biodiversity of psychrotrophic bacteria from the soil of high-elevation regions in Yushan National Park". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/e5bwvm.
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碩士國立臺灣大學
海洋研究所
105
Most of the Earth’s biosphere is permanently cold environment, which temperature is lower than 5 °C, including alpine and polar regions which constitute 25 % of the world’s land surface area, and deep sea, etc. Many psychrotrophs have been isolated from these cold environments. There isn’t any permanently cold environment in Taiwan, for the reason that Taiwan is situated in the subtropical zone. However, the high elevation regions (over 3,000 m) in the Yushan National Park are classified as frigid zones. Therefore, psychrotrophs may abundantly exist in those cold habitats. The purpose of this study was to investigate the compositions and diversity of psychrotrophs in the soil of the high elevation regions of Yushan. Another aim was to find out the novel psychrotrophs existing in the soil of the high elevation regions of Yushan. The soil samples were collected from the different vegetation in the regions of Main, North (3,600 – 3,700 m) and West Peaks (3,402 – 3,518 m) of Yuhsan. This study was conducted using bacterial enumeration and isolation by plate method, detecting the phenotypic characteristics, and the 16S rRNA gene sequences, and constructing the phylogenetic tree by neighbor-joining method. The results revealed that the bacterial abundance of psychrotrophs in the soil of the high elevation regions of Yushan ranged from 2.8 × 106 to 3.5 × 107 (CFU/g wet wt.). About 97 % of isolates were psychrotolerant bacteria. Analysis of the 16S rRNA sequences revealed that 86.7 %, 9.5 %, 1.9 % and 1.9 % of isolates could be divided to four phyla namely Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, respectively. The isolates further distributed into 18 genera, Pseudomonas, Janthinobacterium, Rahnella, Rouxiella, Acinetobacter, Duganella, Flavobacterium, Stenotrophomonas, Collimonas, Variovorax, Luteibacter, Dyella, Caballeronia, Serratia, Arthrobacter, Paenibacillus, Rhodococcus, Oerskovia. In this study, Pseudomonas was the predominant genus (45.7%), follwed by Rahnella (11.4 %) and Janthinobacterium (9.5 %). The result of psychrotrophs composition revealed that the diversity of genera in the regions of West Peak (15 genera) was higher than that in the regions of Main and North Peaks. The result also indicated that Pseudomonas widely distributed in the soil of the high elevation regions of Yushan. Additionally, the sequences similarity of strain H2 in this study and its related type species was lower than 97 %. It meant that strain H2 might have the potential to be proposed as a novel species. According to the result of phylogenetic tree, strain H2 might be a novel species of the genus Glaciimonas.
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Fu, Ching-Fan y 傅靜凡. "Isolation Characterization of Psychrotrophic Histamine-producing Bacterium in Seafoods". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/64066131233869518034.
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碩士國立澎湖科技大學
食品科學研究所
101
Abstract Histamine fish poisoning usually results from the ingestion of fish containing high levels of histamine. Histamine is formed in fish by certain bacteria that can decarboxylate histidine. Most of the histamine-producing bacteria are mesophilic, strict temperature control is important in the prevention of histamine fish poisoning. However, the presence of psychrophilic histamine-producing bacteria also causes the accumulation of histamine at low temperatures. To study those psychrophilic histamine-producing bacteria,27 strains were isolated from Scomber australasicus (mackerel) and Rachycentron canadum (cobia) by HDC gene detection and low temperature screening in this study.All of them were demonstrated as histamine-producing bacteria by histamine immunoassay test kit. In addition to histamine, most of the them were able to produce putrescine and cadaverine . 27 isolated strains were identified as Photobacterium sp, Pseudomonas sp, Psychrobacter sp , Vibrio fischeri by 16S rDNA sequence analysis. In the present study, 5f28 strain(Vibrio fishcheri) and 9f14 strain (Photobacterium phosphoreum) were inoculated into different broth,(TSBNH, mackerel and cobia broth), and examined their behavior during storage at low and room temperature (5℃ and 25℃).In mackerel broth, histamine levels arrived at 582 ppm by 5f28 and 735 ppm by 9f14 at 5℃ in 2 day. In 8 day, the amounts of histamine were 901 ppm and 912 ppm, respectively. These data indicate that histamine accumulation in fish during low temperature storage by psychrotrophic histamine-producing bacteria could be hazards in food safety.
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MIKULOVÁ, Magda. "Psychrotrofní lipolytické bakterie a obsah volných mastných kyselin v bazénových vzorcích syrového kravského mléka". Doctoral thesis, 2012. http://www.nusl.cz/ntk/nusl-115843.
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The objective of the study was to analyze the relationship of psychrotrophic lipolytic bacteria in bulk samples of cow?s raw milk and their metabolic activity based on the content of free fatty acids and identifying the factors that may influence their levels. The contents of free fatty acids (FFA) and counts of total bacteria, psychrotrophic lipolytic bacteria (PLiBC) and somatic cells were determined in 150 samples of cow?s bulk raw milk on 20 farms with three different milking technologies in South Bohemia during 2008?10. FFA were determined using an extraction-titration method. Within the compared technologies, the highest mean values of FFA (38,8 mmol?kg-1; P<0,001) and PLiBC (696 CFU?ml?1) were observed on farms with pipeline milking in stalls. The lowest mean FFA level (15,4 mmol?kg-1) was determined on farms with an automatic milking system. Medium values were determined on farms with parlour milking. From the aspect of the inhibition of an increase in psychrotrophic bacteria, and mainly in psychrotrophic lipolytic bacteria in conditions of cold storage of raw milk the temperature of 4°C seems optimum as it markedly inhibits the growth of mesophilic and psychrotrophic bacteria and at the same time the increase in the values of free fatty acids is slower at this temperature compared to the temperatures of 6,5 and 10°C.
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Lee, Yung-Hua y 李永華. "Identification of gene controlling extracellular protease production from a Psychrotrophic Bacterium Pseudomonas sp. P90". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/84962456987608232763.
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碩士國立中興大學
植物學系
89
Recent resrarch reports that several exo-enzyme activity of genus Pseudomonas were regulated by two-component regulatory system composed of lemA/gacA gene. Pseudomonas sp. P90 which is a psychotrophic bacterium isolated from Ta-Ta-Ja Taiwan in Mountain had both exocellular protease and lipase activity. After mutagenizing with mini transposon pUT-Tn5/(pfm)Tc a strain P90A2 without exocellular protease and lipase activity were isolated. According to the result of Northern blot, the loss of protease activity was due to no transcription of protease gene but not prohibition of secretion. When analyzed the insertion site of the tetracycline resistance gene of transposon in P90A2 chromosomal DNA, We could find three open reading frames (ORF) in a nucleotide sequence of 2691-bp which spanned to the insertion site. When cloned this DNA fragment and analyzed it’s possible gene expression in maxi-cell, one protein with a molecular weight of about 50 kDa was found. This size was in close agreement with the value calculated for e deduce polypeptide product of ORF hypo450, one of the three open reading frame. The alignment analysis of amino acid sequences showed that the deduced polypeptide product of ORF hypo450 was similar to a few hypothetical proteins of several bacteria. Although it had no similarity with LemA and GacA in amino acid sequence, it had many amino acid sites related to tyrosine kinase function, instead a histidine protein kinase like LemA. Therefore, whether the gene product of ORF hypo450 is belonging to HPK or RR of two component regulatory system, or another independent regulatory protein, need further confirmation.
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CHIUN, CHIU WEI y 邱偉鈞. "Metalloprotease from the psychrotrophic bacterium Pseudomonas sp. P90:gene cloning and enzyme purification and characterization". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/83297037934669534717.
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碩士國立中興大學
植物學系
88
Abstract Pseudomonas sp. P90, a gram-negative psychrotrophic bacterium we isolated in the Taiwan Mountain Ta-Ta-Ja about 2700 M alt, secretes a thermostable protease into the culture medium. To clone this protease gene, we used PCR to amplify a part of the protease gene. A plasmid carrying this PCR product and ori was integrated via homologous recombination to the chromosome of wild type P90, and then the chromosome was digested with restriction enzyme followed by self-ligation by treatment with T4 DNA ligase. A clone obtained, pZP1, contained a 6.0-kb insert. Nucleotide sequence analysis of this insert showed highly identity in amino acid sequence to other bacterium eg. Pseudomonas sp. 、 Serratia marcescens and Erwinia chryanthemi witch encodes metalloprotease, inhibitor gene and transporter gene. Then we used pZP1SHP that was made by pZP1 to obtain complete protease gene via homologous recombination again. 3096 bp nucleotide sequences that contained the complete sequences of Pseudomonas sp. P90 protease gene, inhibitor gene and part of transporter gene we obtained. The protease was purified from the culture supernatant of P90 by affinity ion-exchange chromatography with a DEAE-cellulose column and gel filtration on Sephadex G-100. This protease has a molecular weight of about 47 kDa and the optimum temperature and pH for the maximum activity was 40℃and pH 8.0 respectively. In the inhibiter experiment, it was inhibited by EDTA or EGTA . Addition of divalent metal ions like Mg2+、Ca2+、Co2+ and Mn2+ could recover the protease activity of the EDTA treated protease. Therefore, it is a kind of metalloprotease. In this study, a mutant P90A2 that lost the activity of protease and lipase was isolated by transposon (pUT-Tn5 (pfm)/Tc) mutagenesis. For this reasons, we guessed that the protease gene was clustered with the gene for lipase.
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石靜慧. "Cloning and characterization of genes controling extracellular protease production from a psychrotrophic bacterium pseudomonas sp.P90". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/41382392034130884251.
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Huei-Ming, Lin y 林惠敏. "Analysis and Comparison of Gene Regulating Extracellular Protease Production from a Psychrotrophic Bacterium Pseudomonas sp. P90". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/07643297878005290674.
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碩士國立中興大學
植物學系
90
Prokaryotes can respond to a variety of environmental stimuli by means of systems generally composed of two proteins. The first protein is sensory kinase, which has sensor function and kinase activity. The second protein is response regulator. In the genus Pseudomonas, a conserved two-component regulatory system consisting of the GacS and GacA has a decisive role in the control of the production of extracellular enzymes, antibiotics or toxins. Previously, Pseudomonas sp. P90, a gram-negative psychrotrophic bacterium isolated from Ta-Ta-Ja Mountain of middle Taiwan, can produce extracellular proteolytic and lipolytic activity. We designed a pair of primers based on the strickly conserved region of GacS and GacA amino acid sequences, in order to use PCR to identity P90. The results revealed that P90 has gacS and gacA gene. Previously, following transposon pUT-Tn5(pfm)/Tc mutagenesis, an extracellular protease- and lipase-negative mutant, P90A2, was isolated from P90. When we analyzed the insertion site of the tetracycline resistance gene of transposon in P90A2 chromosomal DNA, we could find an open reading frame (ORF) with 1350 bp, designated ORF hypo450. We analyzed the transcript of ORF hypo450 by RT-PCR, the results suggested that ORF hypo450 has no transcript with the size similar to that of the ORF hypo450 coding region. We cloned the pET21a vector with ORF hypo450, then purified the fusion protein and made into serum. Western blotting analysis of total protein separated by SDS-PAGE demonstrated that there is no hypo450 protein in wild type P90. Further, proteolytic activity was not restored to protease- and lipase-negative mutants harboring broad-host-range vector which containing 2619 bp DNA fragment of ORF hypo450 fragment. But the proteolytic activity and lipolytic activity of the mutants（P90A2 and P90pOK421）, was restored by double crossover the ORF hypo450 by homologous recombination. Therefore, we inferred that beside the GacS and GacA, ORF hypo450 also regulated the expression of the extracellular protease and lipase activity of P90.
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Lee, Hui-Chen y 李慧貞. "Lipolytic enzyme from the Psychrotrophic Bacterium Pseudomonas sp. P116：Gene Cloning and enzyme Purification and Characterization". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/45086069506887322912.
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碩士國立中興大學
植物學系
89
In this study, Pseudomonas sp. P116, a gram-negative psychrotrophic bacterium displays extracellular lipolytic and proteolytic activities,was isolated from Ho-Huan Mountain of middle Taiwan. Following shotgun cloning, a DNA fragment containg lipolytic enzyme gene was obtained and sequenced. Analysis of the complete nucleotide sequence of this fragment revealed an open reading frame of 930 nucleotids, which may encode a sequence of 310 amino acids. Alignment comparison showed this amino sequence was homologous to the lipase/esterase of Pseudomonas aeruginosas PAO1 and Bacillus halodurans. Both extracellular lipase and protease have been purified from the culture supernatant of P116 with DEAE-cellulose column. SDS-PAGE revealed their molecular weight were 33 kDa and 50 kDa , respectively. Results of enzymatic activity analysis indicated the optimal temperature and pH for lipase are 35℃and pH 7.0, and for Protease are 37℃and pH 7.0, respectively.
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Vithanage, Nuwan R. "Mapping the thermo-tolerant proteases in ultra high temperature (UHT) treated milk using molecular approaches". Thesis, 2017. https://vuir.vu.edu.au/34726/.
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Refrigerated storage of raw milk selects for psychrotrophic bacterial genera such as Pseudomonas (mainly Pseudomonas fluorescens), Bacillus, Acinetobacter, Hafnia, Klebsiella, Rahnella, Stenotrophomonas and Aeromonas, Serratia, which are disseminated by means of feed, faeces, bedding material, soil, air, water and milking and processing equipment at the farming and processing environments. These bacteria produce a wide range of extracellular proteases that are resistant to the current heating regimes used in Ultra High Temperature (UHT) processing, typically 135-150 °C for 2-10 s. The residual bacterial proteases can lead to the development of quality defects in UHT milk, including bitterness, increased viscosity, sedimentation and age gelation, all of which, cause spoilage and shelf-life deterioration during ambient storage and transportation of UHT milk and dairy products.