The oxidation of acetaldehyde: an issue remained unclear in the acetic acid fermentation

醋酸菌发酵生产醋酸是一种典型的微生物转化乙醇生产醋酸的过程。本研究对醋酸菌巴氏醋杆菌中乙醛脱氢酶（ALDH）催化乙醛氧化为醋酸的特性进行了遗传和生化分析。结果表明，A.巴氏杆菌具有两种ALDH复合物：典型的ALDH复合物对乙酸发酵是必需的，而旁系同源的ALDH复合物对乙酸发酵的贡献较小。两种ALDH复合物的最适pH和对乙醛的亲和力不同。旁系同源的ALDH被纯化为由三个亚基组成的复合物，但典型的ALDH似乎是不稳定的，易于分解成亚基水平。

Acetic acid fermentation by acetic acid bacteria is a typical microbial transformation from ethanol to acetic acid. The present study conducted genetic and biochemical analyses on aldehyde dehydrogenase (ALDH) catalyzing oxidation of acetaldehyde into acetic acid in Acetobacter pasteurianus, a member of acetic acid bacteria. It was shown that A. pasteurianus has two kinds of ALDH complexes: canonical one is essential for acetic acid fermentation, but paralogous one less contributes to that. Two ALDH complexes were different from each other as to pH optima and affinities to acetaldehyde. The paralogous ALDH was purified as complex consists of three subunits, but canonical ALDH seemed to be unstable and prone to be decomposed into subunit level.