巴氏醋酸杆菌沪酿1.01乙醇氧化产醋酸关键酶的研究

Study on the key enzymes of ethanol oxidation and acetic acid production in Acetobacter pasteurianus HN 1.01

乙醇脱氢酶（ADH）和乙醛脱氢酶（ALDH）是巴氏醋酸杆菌乙醇氧化产醋酸的关键酶系。在分批发酵实验中,乙醇脱氢酶（ADH）和乙醛脱氢酶（ALDH）随时间呈动态变化,均于36h达到酶活峰值,分别为8.21U/mg和2.52U/mg,在整个过程中ADH的酶活始终高于ALDH。同时,酶系酶活较高时,产酸速率相应较高,酶活较低时,对应的产酸速率也较低。研究了底物乙醇对酶系的影响：在没有乙醇的发酵条件下,酶系的酶活水平较低,分别为0.38U/mg和0.28U/mg;1%~3%（v/v）乙醇浓度内,酶系酶活随着浓度的升高而升高,超过该范围,随着乙醇浓度的升高,酶活又开始受到抑制。研究了底酸对酶系的影响：在没有底酸的发酵条件下,ALDH酶活较低,ADH与ALDH的酶活之比最高达到了3.3倍（36h）;底酸的存在缩短了发酵时间,产酸速率加快,ADH和ALDH的酶活水平提高,ALDH的酶活最高达到了7.46U/mg。

Alcohol dehydrogenase（ADH） and aldehyde dehydrogenase（ALDH） are the key enzymes of ethanol oxidation and acetic acid production in Acetobacter pasteurianus.ADH and ALDH exhibited dynamic changes in acetic acid batch fermentation,and reached the peak after 36h with specific activities of 8.21U/mg and 2.52U/mg,respectively.Enzyme activity of ADH was always higher than that of ALDH in the whole fermentation process.The acetic acid production rate was high when the enzymes activities were high and vice versa.The effect of ethanol to the enzymes was studied：the two enzymes exhibited low activity when fermentation was performed in medium without ethanol,which was 0.38U/mg and 0.28U/mg,respectively. When performed in medium with 1% ~3% （v/v） ethanol,the enzymes activities were enhanced,and then were inhibited when the ethanol concentration was further raised.The effect of initial acetic acid was also studied：when fermentation was carried out in medium without initial acetic acid,ALDH activity was low,and ADH activity was 3.3 times （36h） higher than ALDH at most. The existence of initial acetic acid shortened the fermentation time and increased the acetic acid production rate,the activity of ADH and ALDH was enhanced accordingly,and the highest ALDH activity reached 7.46U/mg.