Cross protection can undermine the effectiveness of control measures on foodborne pathogens,and therefore brings major implications for food safety.In this work,the capacity of Salmonella Enteritidis to mount ethanol ...Cross protection can undermine the effectiveness of control measures on foodborne pathogens,and therefore brings major implications for food safety.In this work,the capacity of Salmonella Enteritidis to mount ethanol tolerance following acid adaptation was characterized by analysis of cell viability and cell membrane property.It was observed that preadaptation to pH 4.5 significantly(P<0.05)increased the tolerance of log-phase cells to ethanol;in contrast,stationary-phase cells displayed reduced ethanol tolerance after acid adaptation.However,acid adaptation did not cause cell leakage and morphological change in both log-phase and stationary-phase S.Enteritidis.Fatty acid analysis further revealed that the amount of C_(14:0),C_(17:0 cyclo) and C_(19:0 cyclo) fatty acids was increased,while that of C_(16:1ω7c) and C_(18:1ω7c) fatty acids was decreased,respectively,in response to acid adaptation,regardless of bacterial growth phase.Notably,acid adaptation significantly(P<0.05)increased the proportion of C_(16:0) fatty acid in log-phase cells,but this effect did not occur in stationary-phase cells.Moreover,exogenous addition of C_(16:0) fatty acid to stationary-phase acid-adapted cultures was able to enhance bacterial ethanol tolerance.Taken together,C_(16:0) fatty acid is involved in the growth-phase-dependent protective effect of acid adaptation on ethanol tolerance in S.Enteritidis.展开更多
Saccharomyces cerevisiae is the main yeast used in the winemaking industry.Its innate glucophilicity provokes a discrepancy in glucose and fructose consumption during alcoholic fermentation of grape must,which,combine...Saccharomyces cerevisiae is the main yeast used in the winemaking industry.Its innate glucophilicity provokes a discrepancy in glucose and fructose consumption during alcoholic fermentation of grape must,which,combined with the inhibitory effect of ethanol accumulated in the fermentation broth,might lead to stuck or sluggish fermentations.In the present study,we realized an Adaptive Laboratory Evolution strategy,where an alcoholic fermentation of a 20 g/L fructose broth was followed by cell selection in a high ethanol concentration environment,employed in two different S.cerevisiae strains,named CFB and BLR.The evolved populations originated from each strain after 100 generations of evolution exhibited diverse fermentative abilities.One evolved population,originated from CFB strain,fermented a synthetic broth of 100 g/L glucose and 100 g/L fructose to dryness in 170 h,whereas the parental strain did not complete the fermentation even after 1000 h of incubation.The parameters of growth of the parental and evolved populations of the present study,as well as of the ethanol tolerant populations acquired in a previous study,when grown in a synthetic broth of 100 g/L glucose and 100 g/L fructose,were calculated through a kinetic model,and were compared to each other in order to identify the effect of evolution on the biochemical behavior of the strains.Finally,in a 200 g/L fructose synthetic broth fermentation,only the evolved population derived from CFB strain showed improved fermentative behavior than its parental strain.展开更多
基金supported by the National Key Research and Development Program of China(2019YFE0119700)the National Natural Science Foundation of China(32001797)+1 种基金the Science and Technology Innovation Agricultural Project of Shanghai Science and Technology Commission(19391902100)the Natural Science Foundation of Shanghai(22ZR1429900).
文摘Cross protection can undermine the effectiveness of control measures on foodborne pathogens,and therefore brings major implications for food safety.In this work,the capacity of Salmonella Enteritidis to mount ethanol tolerance following acid adaptation was characterized by analysis of cell viability and cell membrane property.It was observed that preadaptation to pH 4.5 significantly(P<0.05)increased the tolerance of log-phase cells to ethanol;in contrast,stationary-phase cells displayed reduced ethanol tolerance after acid adaptation.However,acid adaptation did not cause cell leakage and morphological change in both log-phase and stationary-phase S.Enteritidis.Fatty acid analysis further revealed that the amount of C_(14:0),C_(17:0 cyclo) and C_(19:0 cyclo) fatty acids was increased,while that of C_(16:1ω7c) and C_(18:1ω7c) fatty acids was decreased,respectively,in response to acid adaptation,regardless of bacterial growth phase.Notably,acid adaptation significantly(P<0.05)increased the proportion of C_(16:0) fatty acid in log-phase cells,but this effect did not occur in stationary-phase cells.Moreover,exogenous addition of C_(16:0) fatty acid to stationary-phase acid-adapted cultures was able to enhance bacterial ethanol tolerance.Taken together,C_(16:0) fatty acid is involved in the growth-phase-dependent protective effect of acid adaptation on ethanol tolerance in S.Enteritidis.
文摘Saccharomyces cerevisiae is the main yeast used in the winemaking industry.Its innate glucophilicity provokes a discrepancy in glucose and fructose consumption during alcoholic fermentation of grape must,which,combined with the inhibitory effect of ethanol accumulated in the fermentation broth,might lead to stuck or sluggish fermentations.In the present study,we realized an Adaptive Laboratory Evolution strategy,where an alcoholic fermentation of a 20 g/L fructose broth was followed by cell selection in a high ethanol concentration environment,employed in two different S.cerevisiae strains,named CFB and BLR.The evolved populations originated from each strain after 100 generations of evolution exhibited diverse fermentative abilities.One evolved population,originated from CFB strain,fermented a synthetic broth of 100 g/L glucose and 100 g/L fructose to dryness in 170 h,whereas the parental strain did not complete the fermentation even after 1000 h of incubation.The parameters of growth of the parental and evolved populations of the present study,as well as of the ethanol tolerant populations acquired in a previous study,when grown in a synthetic broth of 100 g/L glucose and 100 g/L fructose,were calculated through a kinetic model,and were compared to each other in order to identify the effect of evolution on the biochemical behavior of the strains.Finally,in a 200 g/L fructose synthetic broth fermentation,only the evolved population derived from CFB strain showed improved fermentative behavior than its parental strain.
