清香型大曲酯化酶活力的研究

摘要

The effects of lactic acid concentration and pH on esterifying enzymes activity were discussed.The results showed that,the lactic acid concentration had great effect on esterifying enzymes activity of Daqu.When the lactic acid concentration was low,the esterifying enzymes showed synthesis effect,catalysing ethyl lactate (lactic acid less than 8 g/L) and ethyl acetate (lactic acid less than 16 g/L) synthesis.When the lactic acid concentration was high,the esterifying enzymes showed hydrolysis effect,so the ester was decomposed into acid and alcohol.pH showed significant effect on esterifying enzymes decomposition activity of Daqu,the decomposition of the ester was mainly chemical decomposition at pH 2.0,and chemical decomposition and esterifying enzymes decomposition both play a role at pH 3.0-6.0.The optimum pH for ethyl acetate synthesis by esterifying enzymes was 4.0,which produced 188.8 mg/L ethyl acetate at 100 h,and for the pH 5.0 buffer,it produced 182.6 mg/L ethyl lactate at 100 h.%研究了乳酸质量浓度和pH对清香型大曲酯化酶活力的影响,结果表明,乳酸质量浓度对大曲酯化酶活力有很大影响,当乳酸质量浓度较低时,大曲中的酯化酶表现为合成作用,分别在低于8g/L和16g/L时催化乳酸乙酯和乙酸乙酯的合成;当乳酸质量浓度较高时,酯化酶表现为水解作用,将酯分解为相应酸和醇;pH对大曲酯化酶酯分解活力影响显著,在pH值为2.0时,酯的分解主要为化学分解,在pH值为3.0～6.0时,化学分解和酯化酶分解都起作用.实验发现在pH值为4.0时大曲酯化酶催化乙酸乙酯合成的活力最强,100h时乙酸乙酯质量浓度达188.8 mg/L;pH值为5.0时催化乳酸乙酯合成的活力最强,100h时乳酸乙酯质量浓度达182.6 mg/L.