Arndt Annette, Auchter Marc, Ishige Takeru, Wendisch Volker F, Eikmanns Bernhard J
Institute of Microbiology and Biotechnology, University of Ulm, Ulm, Germany.
J Mol Microbiol Biotechnol. 2008;15(4):222-33. doi: 10.1159/000107370. Epub 2007 Aug 13.
Corynebacterium glutamicum grows on a variety of carbohydrates and organic acids as single or combined sources of carbon and energy. Here we show the ability of C. glutamicum to grow on ethanol with growth rates up to 0.24 h(-1) and biomass yields up to 0.47 g dry weight (g ethanol)(-1). Mutants of C. glutamicum deficient in phosphotransacetylase (PTA), isocitrate lyase (ICL) and malate synthase (MS) were unable to grow on ethanol, indicating that acetate activation and the glyoxylate cycle are essential for utilization of this substrate. In accordance, the expression profile of ethanol-grown C. glutamicum cells compared to that of glucose-grown cells revealed an increased expression of genes encoding acetate kinase (AK), PTA, ICL and MS. Furthermore, the specific activities of these four enzymes as well as those of alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) were found to be high in ethanol-grown and low in glucose-grown cells. Growth of C. glutamicum on a mixture of glucose and ethanol led to a biphasic growth behavior, which was due to the sequential utilization of glucose before ethanol. Accordingly, the specific activities of ADH, ALDH, AK, PTA, ICL and MS in cells grown in medium containing both substrates were as low as in glucose-grown cells in the first growth phase, but increased 5- to 100-fold during the second growth phase. The results indicate that ethanol catabolism in C. glutamicum is subject to carbon source-dependent regulation, i.e., to a carbon catabolite control.
谷氨酸棒杆菌能够利用多种碳水化合物和有机酸作为单一或混合的碳源和能源。在此我们展示了谷氨酸棒杆菌在乙醇上生长的能力，其生长速率高达0.24 h⁻¹，生物量产量高达0.47 g干重/（g乙醇）⁻¹。缺乏磷酸转乙酰酶（PTA）、异柠檬酸裂解酶（ICL）和苹果酸合酶（MS）的谷氨酸棒杆菌突变体无法在乙醇上生长，这表明乙酸激活和乙醛酸循环对于利用该底物至关重要。相应地，与在葡萄糖上生长的细胞相比，在乙醇上生长的谷氨酸棒杆菌细胞的表达谱显示，编码乙酸激酶（AK）、PTA、ICL和MS的基因表达增加。此外，发现这四种酶以及乙醇脱氢酶（ADH）和乙醛脱氢酶（ALDH）的比活性在乙醇生长的细胞中较高，而在葡萄糖生长的细胞中较低。谷氨酸棒杆菌在葡萄糖和乙醇的混合物上生长导致双相生长行为，这是由于葡萄糖在乙醇之前被顺序利用。因此，在含有两种底物的培养基中生长的细胞中，ADH、ALDH、AK、PTA、ICL和MS的比活性在第一个生长阶段与在葡萄糖生长的细胞中一样低，但在第二个生长阶段增加了5至100倍。结果表明，谷氨酸棒杆菌中的乙醇分解代谢受到碳源依赖性调节，即受到碳分解代谢物控制。
