Research Of Improving Ethyl Caproate Production In Saccharomyces Cerevisiae By Strenthening Fatty Acid Synthesis

Ethyl caproate,an ethyl ester eliciting apple-like flavor,is the characteristic flavor of strong aromatic liquor,which is the most popular and best-selling liquor in China.Whether the ethyl caproate can be largely produced by Saccharomyces cerevisiae is important to the flavor quality of Chinese strong aroma liquor.To enhance the production of ethyl caproate,deletion of FAA1 and OPI1,overexpression of three fatty acid synthesis genes(ACC1,FAS1 and FAS2)were performed to improve the amount of its precursor acyl-CoA.The main research contents and results were as follows:(1)The FAA1-deletion mutant a5?FAA1 and OPI1-deletion mutant ?5?OPI1 were constructed.In liquid fermentation of corn hydrolysate,the production of ethyl caproate by a5?FAA1 and a5?OPI1 were 19.1%and 19.86%higher than that of parental strain a5 respectively,the ethyl octanoate production were improved by 63%and 56.31%.Furthermore,the production of caproic acid produced by a5?FAA1 and a5?OPI1 were improved by 8.0%and 12.4%.(2)The mutants a5F-ACC1 ? ?50-ACC1 were constructed by deletion of FAA1 and OPI1 respectively with overexpression of ACC1.In liquid fermentation of corn hydrolysate,the production of ethyl caproate by a5F-ACC1 and a50-ACC1 were 76.7%and 67.1%higher than that of parental strain a5 respectively,the production of other FAEEs(C8:0,C10:0,C1 2:0,C1 4:0 and C1 6:0)were improved in different degrees.Furthermore,the production of caproic acid produced by?5F-ACC1 and a5O-ACC1 were improved by 32.3%and 35.4%.(3)The mutants a5F-FAS1,a50-FAS,a5F-FAS2 and a50-FAS2 were constructed by deletion of FAA1 and OPI1 with overexpression of FAS1 and FAS2 accordingly.In liquid fermentation of corn hydrolysate,the production of ethyl caproate by a5F-FAS1 and a50-FAS1 were markedly 2.8-,and 1.75-fold higher than that of parental strain a5 respectively,the production of ethyl octanoate were improved by 2.97-and 2.77-fold.Furthermore,the production of caproic acid were improved by 2.55-and 2.62-fold in a5F-FAS1 and a50-FAS1.The ethyl caproate production by a5F-FAS2 and a50-FAS2 were increased by 19%and 30%than that of a5.however,there were no differences compared with a5AFAA1 ? a5AOPI1,the results indicated that overexpression of FAS2 gene individually had no obvious effect to improve the ethyl caproate production.In addition,it is the first time that this study found overexpression of FAS1 gene can improve the production of ethyl acetate in Chinese liquor,the production of ethyl acetate in a5F-FAS1 and a50-FAS1 were increased by 1.31-and 2.61-folds compared with parental strain a5 respectively.