Construction And Fermentation Of FAA1 Gene Knockout Yeast Strain

Esters are key odorants that provide "fruity" aroma in beer.Esters of matter what determines the quality of beer,in beer contains numerous esters material chain fatty acid ethyl ester are major contributors to the beer good flavor,is an important carrier of beer aroma,mainly including,octanoic acid ethyl ester,ethyl caproate decanoic acid ethyl ester,which with the fresh fennel aroma,ethyl caproate and octanoic acid ethyl ester with a sweet apple aroma,Ethyl decanoate has a rose scent.Ester synthesis pathway in yeast mainly through the beginning,the way is starting point by the sugar glucose metabolic pathways into acetyl coenzyme A,in carboxylase and alcohol acyltransferase by corresponding alcohols and under the action of acyl coenzyme A in synthesis of ester,in this way to generate chain fatty acid ethyl ester by acetyl-co A carboxylase content.In this paper,the effects of the expression of long-chain saturated fatty acid acyl-coa synthetase encoding gene FAA1 in Saccharomyces cerevisiae on the yield of mid-chain fatty acid ethyl ester were studied.The long-chain saturated fatty acid acyl-co A synthase encoded by FAA1 gene is mainly responsible for absorbing exogenous long-chain fatty acids and converting them into acyl-Co A.The long-chain acyl Co A synthase in yeast produces negative feedback inhibition to acetyl Co A carboxylase.The higher the content of long-chain Acyl Co A synthase is,the lower the content of acetyl Co A carboxylase is,which leads to the decrease of the production of medium chain fatty acid ethyl ester ethyl ester.Industrial beer yeast strain TCCC 31194 was selected as the research object to explore the effect of FAA1(Sc FAA1,Seub FAA1)gene knockout on saccharomyces cerevisiae beer fermentation capacity.FAA1 ΔX,FAA1 ΔY and FAA1 ΔXΔY were constructed.The results showed that the deletion of Sc FAA1 and Seub FAA1 genes had no significant effect on the fermentation capacity of S.cerevisiae,but the deletion of Seub FAA1 genes significantly increased the number of yeast and the metabolic rate of sugar in beer at the early stage of fermentation.Fermentation results showed that Sc FAA1 and Seub FAA1 gene knockout had no effect on the content of aromatic alcohols in beer.The fermentation results of FAA1ΔXΔY double knockout strain showed that the metabolism of chain fatty acid ethyl ester in FAA1 ΔXΔY double knockout strain could be affected.The contents of C6-C10 fatty acid ethyl ester such as caproate ethyl ester,capryate ethyl ester and capric acid ethyl ester in beer fermentation broth were increased to 56.23%,47.12% and 26.34%,respectively.The contents of ethyl acetate and iso-amyl acetate increased by 32.37% and 49.25%,respectively.This is due to the elimination of FAA1 gene to remove the negative feedback inhibition of long chain acyl Co A synthase on acetyl Co A carboxylase,thereby increasing the production of medium chain fatty acid ethyl ester.