Effects of ATF2 Overexpression with BAT2 Deletion on the Higher Alcohols and Esters in Beer Yeast

Abstract

During the process of beer fermentation, higher alcohols and esters are two important substances influencing beer flavor. Deletion of BAT2 gene coding amino acid transaminase can effectively reduce production of higher alcohols. On the other hand, alcohol acetyltransferase (AATase) encoded by the ATF2 gene is one of the most important enzymes for acetate ester synthesis. The objective of this study is to construct engineered brewer’s yeast strains for moderate production of acetate esters and less yield of higher alcohols. The industrial beer yeast strain S5 was selected as the parental strain, by means of overexpressing ATF2 and knocking out BAT2 to appropriately increase the concentration of acetate and reduce the concentration of higher alcohols. The engineered strain S5-L, featuring partial BAT2 allelic genes replaced by the constructed ATF2 overexpression cassette, was obtained. The fermentation results indicated that the engineered strain S5-L had a moderate accrete of ethyl acetate compared with the parental strain. The concentration of ethyl acetate produced by the engineered strains S5-L increased to 7.6 mg L−1, about 1.28-fold higher than that produced by the parental S5 cells. The concentration of higher alcohols produced by the engineered strains S5-L reduced to 51.49 mg L−1, about 84.77% of the parental S5 cells. Isobutanol and propanol reduced to 8.30 and 9.72 mg L−1, which was 73.13% and 79.47% of that of the parental strain S5, respectively. Research on the beer yeast genes ATF2 and BAT2 influencing the generation amount of higher alcohol and volatile esters lays a foundation to improve the flavor and quality of beer.