Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
J Biosci Bioeng. 2013 Jan;115(1):32-6. doi: 10.1016/j.jbiosc.2012.07.017. Epub 2012 Aug 16.
Wild-type Acetobacter aceti NBRC 14818 possesses genes encoding isocitrate lyase (aceA) and malate synthase (glcB), which constitute the glyoxylate pathway. In contrast, several acetic acid bacteria that are utilized for vinegar production lack these genes. Here, an aceA-glcB knockout mutant of NBRC 14818 was constructed and used for investigating the role of the glyoxylate pathway in acetate productivity. In medium containing ethanol as a carbon source, the mutant grew normally during ethanol oxidation to acetate, but exhibited slower growth than that of the wild-type strain as the accumulated acetate was oxidized. The mutant grew similarly to that of the wild-type strain in medium containing glucose as a carbon source, indicating that the glyoxylate pathway was not necessary for glucose utilization. However, in medium containing both ethanol and glucose, the mutant exhibited significantly poorer growth and lower glucose consumption compared to the wild-type strain. Notably, the mutant oxidized ethanol nearly stoichiometrically to acetate, which was retained in the medium for a longer period of time than the acetate produced by wild-type strain. The features of the aceA-glcB knockout mutant revealed here indicate that the lack of the glyoxylate pathway is advantageous for industrial vinegar production by A. aceti.
野生型醋化醋杆菌 NBRC 14818 拥有编码异柠檬酸裂解酶 (aceA) 和苹果酸合酶 (glcB) 的基因，这些基因构成了乙醛酸途径。相比之下，用于生产醋的几种醋酸菌缺乏这些基因。在这里，构建了 NBRC 14818 的 aceA-glcB 敲除突变体，并用于研究乙醛酸途径在乙酸产量中的作用。在含有乙醇作为碳源的培养基中，突变体在乙醇氧化为乙酸的过程中正常生长，但随着积累的乙酸被氧化，其生长速度比野生型菌株慢。突变体在含有葡萄糖作为碳源的培养基中的生长与野生型菌株相似，表明乙醛酸途径不是葡萄糖利用所必需的。然而，在含有乙醇和葡萄糖的培养基中，突变体的生长明显比野生型菌株差，葡萄糖消耗也较低。值得注意的是，突变体几乎将乙醇氧化为乙酸，而乙酸比野生型菌株产生的乙酸在培养基中保留的时间更长。这里揭示的 aceA-glcB 敲除突变体的特征表明，乙醛酸途径的缺失有利于醋化醋杆菌的工业醋生产。
