本文主要研究了不同酸浓度和pH值下清香型、浓香型和酱香型大曲的酯化酶催化合成乙酸乙酯、乳酸乙酯、己酸乙酯和丁酸乙酯的不同特性。结果显示，随着酸浓度的升高，三种香型大曲催化合成乙酸乙酯、己酸乙酯的酶活力均是先升高后降低的趋势，催化合成乳酸乙酯的酶活力随乳酸浓度的升高降低；而催化合成丁酸乙酯的酶活力变化趋势三种香型大曲有所不同，清香型和浓香型大曲的酶活力随丁酸浓度的升高先升高后降低，酱香型大曲的酶活力则是逐渐升高。清香型、浓香型和酱香型大曲催化合成乙酸乙酯的最适pH均为4.0，催化合成乳酸乙酯的最适pH分别为7.0、7.0、8.0，催化合成己酸乙酯的最适pH分别为5.0、4.0、4.5，催化合成丁酸乙酯的最适pH分别为4.5、4.0和3.0。综上，不同香型大曲酯化酶的催化特性各有不同，且每种酯的合成都有其合适的酸浓度和pH范围。

The different characteristics of esterifying enzyme catalytic synthesis of ethyl acetate, ethyl lactate, ethyl hexanoate and ethyl butyrate in light-flavor Daqu, strong- flavor Daquand maotai-flavor Daqu were studied in this paper under the different acid concentration (or pH). The results showed that the esterifying enzymes activities of three kinds of Daqu increased at first and then decreased with the increase of acid concentration in catalyzing and synthesizing ethyl acetate, ethyl caproate, the enzyme activity decreased with the increase of lactic acid concentration in catalyzing and synthesizing ethyl lactate. However, the variation tendency of enzyme activity was different in three kinds of Daqu in catalyzing and synthesizing ethyl butyrate. As the butyric acid increased, the enzyme activity of light-flavor Daqu and strong- flavor Daqu increased at first and then decreased, while the enzyme activity of maotai-flavor Daqu increased gradually. For light-flavor Daqu, strong- flavor Daqu and maotai-flavor Daqu, the optimum pH in catalyzing and synthesizing ethyl acetate all were 4.0; the optimum pH in catalyzing and synthesizing ethyl lactate were 7.0, 7.0, 8.0, respectively; the optimum pH in catalyzing and synthesizing ethyl caproate were 5.0, 4.0, 4.5, respectively; the optimum pH in catalyzing and synthesizing ethyl butyrate were 4.5, 4.0, 3.0, respectively. In conclusion, the characteristics of esterifying enzymes of three kinds of Daqu were different, and the synthesis of eash ester had its proper acid concentration and pH range.

国家重点研发计划（2016YFD0400505）；中国博士后科学基金面上项目（2017M611169）