The storage and transportation of raw milk at low temperatures promote the growth of psychrotrophic bacteria and the production of thermo-stable enzymes, which pose great threats to the quality and shelf-life of dairy...The storage and transportation of raw milk at low temperatures promote the growth of psychrotrophic bacteria and the production of thermo-stable enzymes, which pose great threats to the quality and shelf-life of dairy products. Though many studies have been carried out on the spoilage potential of psychrotrophic bacteria and the thermo-stabUities of the enzymes they produce, further detailed studies are needed to devise an effective strategy to avoid dairy spoilage. The purpose of this study was to explore the spoilage potential of psychrotrophic bacteria from Chinese raw milk samples at both room temperature （28 ℃） and refrigerated temperature （7 ℃）. Species of Yersinia, Pseudomonas, Serratia, and Chryseobacterium showed high proteolytic activity. The highest proteolytic activity was shown by Yersinia intermedia followed by Pseudomonas fluorescens （d）. Lipolytic activity was high in isolates of Acinetobacter, and the highest in Acinetobacter guillouiae. Certain isolates showed positive ^-galactosidase and phospholipase activity. Strains belonging to the same species sometimes showed markedly different phenotypic characteristics. Proteases and lipases produced by psychrotrophic bacteria retained activity after heat treatment at 70, 80, or 90 ℃, and proteases appeared to be more heat-stable than lipases. For these reasons, thermo-stable spoilage enzymes produced by a high number of psychrotrophic bacterial isolates from raw milk are of major concern to the dairy industry. The results of this study provide valuable data about the spoilage potential of bacterial strains in raw milk and the thermal resistance of the enzymes they produce.展开更多
Microorganisms living in polar zones play an important part as the potential source of organic activity materials with low temperature characteristics in the bio-technological applications. A psychrotrophic bacterium ...Microorganisms living in polar zones play an important part as the potential source of organic activity materials with low temperature characteristics in the bio-technological applications. A psychrotrophic bacterium (strain Ar/w/b/75°/10/5) , producing cellulose at low temperatures during late-exponential and early-stationary phases of cell growth, was isolated from sea ice-covered surface water in Chuckchi Sea, Arctic. This bacterium, with rod cells, was Gram-negative, slightly halophilic. Colony growing on agar plate was in black. Optimum growth temperature was 15℃. No cell growth was observed at 351 or above. Optimum salt concentration for cell growth was between 2 and 3 % of sodium chloride in media. Maximal cellulase activity was detected at a temperature of 35℃ and pH8. Cellulase was irreversibly inactivated when incubated at 55℃ within 30 min. Enzyme can be kept stable at the temperature no higher than 25℃. Of special interest was that this bacterium produced various extracellular enzymes including cellulase, amylase, agar hydrolase and protease, at low or moderate temperature conditions, which is certainly of it potential value for applications.展开更多
The aim of this research work was to explore psychrotrophic microbes from soil sample of NyAlesund, Svalbard, arctic region and to investigate their potential use as an effective tool for industrial application. A nov...The aim of this research work was to explore psychrotrophic microbes from soil sample of NyAlesund, Svalbard, arctic region and to investigate their potential use as an effective tool for industrial application. A novel psychrotrophic bacterial strain showed good growth on minimal medium containing lipid as the only carbon source. Microbiological characterisation of the isolate showed that it was a gram negative rod. The strain was tested for the production of extracellular lipase enzyme. The enzymes were partially purified by 90% saturated ammonium sulfate and dialysis for desalting. The bacterium was identified as Pseudomonas sp ADT3 by 16S rRNA amplification and sequencing which had been deposited in the NCBI GenBank with accession number JX914667. Phylogenetic tree was also constructed with MEGA5 software and showed the highest level of sequence similarity with Pseudomonas sp. HC3-13 strain. The microorganism had a growth optimum at pH 8.0 and temperature 22°C. Optimization of different parameters e.g. temperature, pH, incubation time, cofactors etc. was performed for the extracellular lipase activity. The hydrolytic activity of the enzyme was enhanced 5 times by Pb2+ but strongly inhibited by heavy metals Hg2+ as well as EDTA and β-mercaptoethanol. For the molecular weight estimation of enzyme SDS-PAGE was done which showed an inducible band of approximately 13.9 KDa. Activity staining and mass spectrometry techniques were also performed.展开更多
The occurrence and the detection system of mesophilic and psychrotrophic aerobic sporulating microorganisms （MPAS） in raw cow＇s milk were studied. Samples of raw cow＇s bulk tank milk were taken 21 times in 14 farm...The occurrence and the detection system of mesophilic and psychrotrophic aerobic sporulating microorganisms （MPAS） in raw cow＇s milk were studied. Samples of raw cow＇s bulk tank milk were taken 21 times in 14 farms during one year. Basis of the method for MPAS assessment is the milk sample inactivation at the temperature 80-82 ℃ for 30 minutes followed by incubation in cultivation dishes at 30 -4- 1 ℃ for 3 days-mesophilic aerobic sporulates （MAS）, and at 6.5 .4- 1 ℃ for 10 days-psychrotrophic aerobic sporulates （PAS）. The total count of MPAS was within the span 2.5-340 CFU/mL （colony forming units）. Average plate count of MPAS was 59.4 CFU/mL with variation coefficient 93.1%. MPAS count found in the same dishes at incubation for mesophilic and subsequently strictly psychrophilic microorganisms （MAS ＋ SPAS） which enables to exclude overestimation of results by sporulates able to grow at both incubation temperatures was on average 56.9 CFU/mL what represents 95.8% out of the number of sums of individual dishes at two temperatures （MAS ＋ PAS）. Correlation coefficient of these two types of results r = 0.99 gives evidence of close dependence that is expressed by linear regression equation y = 0.9773x. We can consider the method using at first 30 .4- 1 ℃ and subsequently 6.5 -4-1℃ （MAS ＋ SPAS） as more correct than the method with the opposite order of cultivation temperatures because of better regression coefficient of linear dependence and higher correlation coefficient in relation to the sum of independent incubations （MAS ＋ PAS）.展开更多
[Objectives]This study was conducted to investigate the influence mechanisms of microbial succession in raw milk under cold storage at different temperatures.[Methods]A raw milk sample was collected from a local large...[Objectives]This study was conducted to investigate the influence mechanisms of microbial succession in raw milk under cold storage at different temperatures.[Methods]A raw milk sample was collected from a local large-scale farm in Tangshan and divided into four treatment gradients:a control group(M)rapidly frozen at-80℃,and three experimental groups stored at 4℃(T),6℃(F),and 8℃(Y),respectively.A time series experiment was carried out according to time intervals of 24,48 and 72 h in each experimental group.Traditional microbial culture methods and 16S rRNA high-throughput sequencing were combined to analyze the dynamic changes in microbial abundance and structural variation.[Results]Plate counting revealed significantly lower total bacterial count and psychrotrophic bacteria in the 4℃storage group within 24 h compared with other treatment groups(P<0.01),confirming that maintaining low-temperature cold chain integrity and controlling treatment time(<24 h)can effectively inhibit microbial metabolic activity.16S rRNA sequencing analysis revealed high initial microbial diversity in raw milk,with dominant genera being Lactococcus,Acinetobacter,and Pseudomonas.Low-temperature treatment effectively reduced theαdiversity index of the microbial community.During the later stage of cold storage at 4℃,the relative abundance of Pseudomonas increased to over 90%,making it the dominant bacterial genus.[Conclusions]This study has significant application value for maintaining the quality of milk and dairy products and prolonging their shelf life.展开更多
A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlor...A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.展开更多
[Objective] The research aimed to initially study degradation effect of the CODc, in sewage by two psychrotrophs. [Method] Two psychrotrophs were isolated from the activated sludge of wastewater treatment plant in Tia...[Objective] The research aimed to initially study degradation effect of the CODc, in sewage by two psychrotrophs. [Method] Two psychrotrophs were isolated from the activated sludge of wastewater treatment plant in Tianjin Konggang Economic Area. CODc, degradation ability of the screened psychrotroph was analyzed in simulated domestic wastewater at 6℃. [Result] K 36 was identified as Comamonas testosterone, and K 38 was identified as Serratia fonticola. CODcr degradation abilities of the two strains were different in test. COOcr removal rates of the K 36 and K 38 respectively reached up to 23% and 53%. The measured result of growth rate suggested that two psychrotrophs both had high activities at low temperature. [ Conclusion] K 36 and K 38 had potentials in wastewater treatment application.展开更多
The diversity and cold adaptation of endophytic fungi associated with five dominant plant species collected from the Baima Snow Mountain(altitude 4,000–4,300 m),Southwest China,were investigated.A total of 604 cultur...The diversity and cold adaptation of endophytic fungi associated with five dominant plant species collected from the Baima Snow Mountain(altitude 4,000–4,300 m),Southwest China,were investigated.A total of 604 culturable endophytic fungi were isolated from 800 stems and leaf segments.The colonization rate of endophytic fungi in the five plant species ranged from 54%to 91%,and the colonization rate of endophytic fungi in the stems was significantly higher(87%)than that in the leaves(67%)(X∼2045.172,P<0.001,chi-squared test).Based on the morphological characteristics and the ITS sequence analysis,the isolates were identified to 43 taxa,of which Cephalosporium,Sirococcus,Penicillium and Aspergillus were the dominant genera,and their relative frequencies were 14.06%,12.58%,9.44%and 7.95%,respectively.The Shannon-Weiner diversity indices and the Sorenson’s coefficient similarity indices of the endophytic fungi from the five plant species ranged from 1.25 to 2.70 and 0.53 to 0.67,respectively.Growth temperature tests indicated that 75%of the isolates from the Baima Snow Mountain were psychrotrophs and 14%were the transitional type between psychrotrophs and mesophiles,whereas all of the isolates from the Yuanjiang Dry-hot Valley were mesophiles,which suggested that the endophytes from the Baima Snow Mountain possess a remarkable ability to adapt to cold environments.展开更多
基金Project supported by the National Natural Science Foundation of China(No.31772080)the Major Science and Technology Projects of Zhejiang Province(No.2015C02039),China
文摘The storage and transportation of raw milk at low temperatures promote the growth of psychrotrophic bacteria and the production of thermo-stable enzymes, which pose great threats to the quality and shelf-life of dairy products. Though many studies have been carried out on the spoilage potential of psychrotrophic bacteria and the thermo-stabUities of the enzymes they produce, further detailed studies are needed to devise an effective strategy to avoid dairy spoilage. The purpose of this study was to explore the spoilage potential of psychrotrophic bacteria from Chinese raw milk samples at both room temperature （28 ℃） and refrigerated temperature （7 ℃）. Species of Yersinia, Pseudomonas, Serratia, and Chryseobacterium showed high proteolytic activity. The highest proteolytic activity was shown by Yersinia intermedia followed by Pseudomonas fluorescens （d）. Lipolytic activity was high in isolates of Acinetobacter, and the highest in Acinetobacter guillouiae. Certain isolates showed positive ^-galactosidase and phospholipase activity. Strains belonging to the same species sometimes showed markedly different phenotypic characteristics. Proteases and lipases produced by psychrotrophic bacteria retained activity after heat treatment at 70, 80, or 90 ℃, and proteases appeared to be more heat-stable than lipases. For these reasons, thermo-stable spoilage enzymes produced by a high number of psychrotrophic bacterial isolates from raw milk are of major concern to the dairy industry. The results of this study provide valuable data about the spoilage potential of bacterial strains in raw milk and the thermal resistance of the enzymes they produce.
基金This work was supported in part by State Oceanic Administration(No.99614)the State Ministry of Science and Technology(No.2001 DIA50040 6)National Nature Science Foundation of China(No.40006010).
文摘Microorganisms living in polar zones play an important part as the potential source of organic activity materials with low temperature characteristics in the bio-technological applications. A psychrotrophic bacterium (strain Ar/w/b/75°/10/5) , producing cellulose at low temperatures during late-exponential and early-stationary phases of cell growth, was isolated from sea ice-covered surface water in Chuckchi Sea, Arctic. This bacterium, with rod cells, was Gram-negative, slightly halophilic. Colony growing on agar plate was in black. Optimum growth temperature was 15℃. No cell growth was observed at 351 or above. Optimum salt concentration for cell growth was between 2 and 3 % of sodium chloride in media. Maximal cellulase activity was detected at a temperature of 35℃ and pH8. Cellulase was irreversibly inactivated when incubated at 55℃ within 30 min. Enzyme can be kept stable at the temperature no higher than 25℃. Of special interest was that this bacterium produced various extracellular enzymes including cellulase, amylase, agar hydrolase and protease, at low or moderate temperature conditions, which is certainly of it potential value for applications.
文摘The aim of this research work was to explore psychrotrophic microbes from soil sample of NyAlesund, Svalbard, arctic region and to investigate their potential use as an effective tool for industrial application. A novel psychrotrophic bacterial strain showed good growth on minimal medium containing lipid as the only carbon source. Microbiological characterisation of the isolate showed that it was a gram negative rod. The strain was tested for the production of extracellular lipase enzyme. The enzymes were partially purified by 90% saturated ammonium sulfate and dialysis for desalting. The bacterium was identified as Pseudomonas sp ADT3 by 16S rRNA amplification and sequencing which had been deposited in the NCBI GenBank with accession number JX914667. Phylogenetic tree was also constructed with MEGA5 software and showed the highest level of sequence similarity with Pseudomonas sp. HC3-13 strain. The microorganism had a growth optimum at pH 8.0 and temperature 22°C. Optimization of different parameters e.g. temperature, pH, incubation time, cofactors etc. was performed for the extracellular lipase activity. The hydrolytic activity of the enzyme was enhanced 5 times by Pb2+ but strongly inhibited by heavy metals Hg2+ as well as EDTA and β-mercaptoethanol. For the molecular weight estimation of enzyme SDS-PAGE was done which showed an inducible band of approximately 13.9 KDa. Activity staining and mass spectrometry techniques were also performed.
文摘The occurrence and the detection system of mesophilic and psychrotrophic aerobic sporulating microorganisms （MPAS） in raw cow＇s milk were studied. Samples of raw cow＇s bulk tank milk were taken 21 times in 14 farms during one year. Basis of the method for MPAS assessment is the milk sample inactivation at the temperature 80-82 ℃ for 30 minutes followed by incubation in cultivation dishes at 30 -4- 1 ℃ for 3 days-mesophilic aerobic sporulates （MAS）, and at 6.5 .4- 1 ℃ for 10 days-psychrotrophic aerobic sporulates （PAS）. The total count of MPAS was within the span 2.5-340 CFU/mL （colony forming units）. Average plate count of MPAS was 59.4 CFU/mL with variation coefficient 93.1%. MPAS count found in the same dishes at incubation for mesophilic and subsequently strictly psychrophilic microorganisms （MAS ＋ SPAS） which enables to exclude overestimation of results by sporulates able to grow at both incubation temperatures was on average 56.9 CFU/mL what represents 95.8% out of the number of sums of individual dishes at two temperatures （MAS ＋ PAS）. Correlation coefficient of these two types of results r = 0.99 gives evidence of close dependence that is expressed by linear regression equation y = 0.9773x. We can consider the method using at first 30 .4- 1 ℃ and subsequently 6.5 -4-1℃ （MAS ＋ SPAS） as more correct than the method with the opposite order of cultivation temperatures because of better regression coefficient of linear dependence and higher correlation coefficient in relation to the sum of independent incubations （MAS ＋ PAS）.
基金Supported by Tangshan Talent Funding Project(A202202005)Dairy Industry Revitalization Major Technological Innovation Project of Hebei Key Research and Development Program(19227516D)High-level Talents Funding Project of Hebei Province(A201803034).
文摘[Objectives]This study was conducted to investigate the influence mechanisms of microbial succession in raw milk under cold storage at different temperatures.[Methods]A raw milk sample was collected from a local large-scale farm in Tangshan and divided into four treatment gradients:a control group(M)rapidly frozen at-80℃,and three experimental groups stored at 4℃(T),6℃(F),and 8℃(Y),respectively.A time series experiment was carried out according to time intervals of 24,48 and 72 h in each experimental group.Traditional microbial culture methods and 16S rRNA high-throughput sequencing were combined to analyze the dynamic changes in microbial abundance and structural variation.[Results]Plate counting revealed significantly lower total bacterial count and psychrotrophic bacteria in the 4℃storage group within 24 h compared with other treatment groups(P<0.01),confirming that maintaining low-temperature cold chain integrity and controlling treatment time(<24 h)can effectively inhibit microbial metabolic activity.16S rRNA sequencing analysis revealed high initial microbial diversity in raw milk,with dominant genera being Lactococcus,Acinetobacter,and Pseudomonas.Low-temperature treatment effectively reduced theαdiversity index of the microbial community.During the later stage of cold storage at 4℃,the relative abundance of Pseudomonas increased to over 90%,making it the dominant bacterial genus.[Conclusions]This study has significant application value for maintaining the quality of milk and dairy products and prolonging their shelf life.
文摘A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.
基金Supported by Excellent Talent Support Plan Project in New Century, Ministry of Education,China(NCET-09-0586)Special Project of the Science Research in Public Welfare Industry,Ministry of Water Resources,China (201101018,201201114)Special Item of the National International Science and Technology Cooperation(S2013BGR0244)
文摘[Objective] The research aimed to initially study degradation effect of the CODc, in sewage by two psychrotrophs. [Method] Two psychrotrophs were isolated from the activated sludge of wastewater treatment plant in Tianjin Konggang Economic Area. CODc, degradation ability of the screened psychrotroph was analyzed in simulated domestic wastewater at 6℃. [Result] K 36 was identified as Comamonas testosterone, and K 38 was identified as Serratia fonticola. CODcr degradation abilities of the two strains were different in test. COOcr removal rates of the K 36 and K 38 respectively reached up to 23% and 53%. The measured result of growth rate suggested that two psychrotrophs both had high activities at low temperature. [ Conclusion] K 36 and K 38 had potentials in wastewater treatment application.
基金supported by the Natural Science Foundation of Yunnan Province and the Science Foundation of Yunnan Educational Committee(2011Y381).
文摘The diversity and cold adaptation of endophytic fungi associated with five dominant plant species collected from the Baima Snow Mountain(altitude 4,000–4,300 m),Southwest China,were investigated.A total of 604 culturable endophytic fungi were isolated from 800 stems and leaf segments.The colonization rate of endophytic fungi in the five plant species ranged from 54%to 91%,and the colonization rate of endophytic fungi in the stems was significantly higher(87%)than that in the leaves(67%)(X∼2045.172,P<0.001,chi-squared test).Based on the morphological characteristics and the ITS sequence analysis,the isolates were identified to 43 taxa,of which Cephalosporium,Sirococcus,Penicillium and Aspergillus were the dominant genera,and their relative frequencies were 14.06%,12.58%,9.44%and 7.95%,respectively.The Shannon-Weiner diversity indices and the Sorenson’s coefficient similarity indices of the endophytic fungi from the five plant species ranged from 1.25 to 2.70 and 0.53 to 0.67,respectively.Growth temperature tests indicated that 75%of the isolates from the Baima Snow Mountain were psychrotrophs and 14%were the transitional type between psychrotrophs and mesophiles,whereas all of the isolates from the Yuanjiang Dry-hot Valley were mesophiles,which suggested that the endophytes from the Baima Snow Mountain possess a remarkable ability to adapt to cold environments.
