【摘要】 为了考察苹果酸酶对厌氧混合酸发酵的影响,从E.coliDH5α中PCR扩增苹果酸酶(NAD+-dependent,E.C1.1.1.38)基因sfcA,插入质粒pTrc99a构建了表达质粒pTrc99a-sfcA,有氧和厌氧的条件下,IPTG诱导在E.coliFMJ39(ldh,pfl)中均获得大量表达。厌氧发酵结果表明,过量表达苹果酸酶会影响混合酸发酵中甲酸、乙酸、丁二酸途径。重组菌甲酸和乙酸的量分别比受体菌提高了17.58%和15.27%,丁二酸的量降低了26.87%,柠檬酸的量变化不大。实验证实即使pfl基因缺陷,高浓度的L-Thr和L-Ser也会诱导Tdc操纵元把丙酮酸转化为甲酸和乙酸。更多还原

【Abstract】 In order to investigate the effect of malic enzyme on anaerobic mixed acid fermentation,the gene encoding NAD+-dependent malic enzyme was amplified from E.coli DH5α genome by using PCR and cloned into vector pTrc99a to give an expression vector pTrc99a-sfcA.Malic enzyme was overproduced by E.coli FMJ39(ldh,pfl)harboring pTrc99a-sfcA under the condition of IPTG induction.The results of anaerobic fermentation indicated overexpression of malic enzyme would have influence on the pathway of formate,acetate and succinate of FMJ39.The concentration of formate and acetate was 17.58% and 15.27% higher than FMJ39,the succinate concentration was reduced by 26.87%.There was no obvious citrate concentration change.The experimental results also indicated that high concentration of L-Thr and L-Ser would induce the Tdc operon to convert pyruvate into formate and acetate even when pfl gene encoding the pyruvate formate lyase was inactivated.更多还原