适量产乙酸酯酿酒酵母菌株的选育

Breeding of Saccharomyces cerevisiae strains with appropriate yield of acetate esters

乙酸乙酯、乙酸异戊酯等酯类物质是白酒中重要的风味物质,含量过低会导致酒体风味寡淡,而过高会破坏整体香气的平衡。实验室前期以工业酿酒酵母AY12的单倍体a45为出发菌株,构建了低产高级醇高产酯酿酒酵母菌株a45-AWT,但其存在乙酸异戊酯含量过高的问题,影响白酒品质。通过过表达编码乙酸异戊酯水解酶的基因IAH1的方法,可达到调控高产酯酵母乙酸异戊酯产量的目的。采用胞内同源重组的方法,在a45-AWT菌株的Gal80位点过表达IAH1基因,获得a45-BAI菌株。模拟白酒发酵结果表明,与高产酯酵母a45-AWT相比,a45-BAI的乙酸异戊酯的质量浓度仅为10.73 mg/L,降低了83.2%,乙酸乙酯和乙酸异戊酯的质量浓度比提高了87.3%。该研究通过调节酯合成、分解途径成功选育了具有高产乙酸乙酯、适量产乙酸异戊酯低产高级醇性状的酿酒酵母菌株,为白酒酿造用菌的选育提供了新思路。

Ethyl acetate and isoamyl acetate are two important volatile flavor substances in Chinese Baijiu.Low concentration of ester could not give Baijiu the characteristic taste,while the flavor of Baijiu was also damaged by hyper-production of ester.In previous work,ATF1 overexpression with BAT2 deletion in Saccharomyces cerevisiae a45(a45-AWT)enhanced the content of acetate esters and decreased the content of higher alcohols.However,the concentration of isoamyl acetate was quite high,thereby causing negative effects on the quality of Baijiu.In this work,isoamyl acetate hydrolyzing esterase coding gene IAH1 was deleted to evaluate the effect on the content of acetate esters and higher alcohols in Baijiu.The strain a45-AWT was used as the parental strain.IAH1 was overexpressed and a45-BAI strain was obtained.Fermentation analysis showed that the isoamyl acetate production of a45-BAI was only 10.73 mg/L,which was decreased by 83.2%.The proportion of ethyl acetate and isoamyl acetate of strain a45-BAI was increased by 87.3%.In this study,The strain with high yield of ethyl acetate was constructed by regulating the of ester biosynthesis and biolysis.It could moderate production of isoamyl acetate and low production of higher alcohols.The results provided new strategies for strain breeding.