Tomar A, Eiteman M A, Altman E
Center for Molecular BioEngineering, Department of Biological and Agricultural Engineering, University of Georgia, Athens GA 30602, USA.
Appl Microbiol Biotechnol. 2003 Jul;62(1):76-82. doi: 10.1007/s00253-003-1234-6. Epub 2003 Feb 26.
We compared pyruvate accumulation in six strains of Escherichia coli and their corresponding ppc mutants. Each strain contained a mutation of a gene involved in the pathway to acetate synthesis. Strains with mutations in genes encoding the pyruvate dehydrogenase complex generally exhibited the greatest pyruvate accumulation of which CGSC6162 (an aceF mutant) and CGSC6162 Delta ppc were studied in greater detail in controlled fermenters. Both CGSC6162 and CGSC6162 Delta ppc accumulated greater than 35 g/l pyruvate in a medium supplemented with acetate. We observed pyruvate mass yields from glucose of 0.72 in CGSC6162, with volumetric productivities above 1.5 g l(-1) h(-1). For CGSC6162 Delta ppc, we observed pyruvate yields of 0.78 and volumetric productivities above 1.2 g l(-1) h(-1). CGSC6162 consumed all initially supplied acetate, while CGSC6162 Delta ppc first consumed and then generated acetate during the course of a 36 h fermentation. Acetate generation and pyruvate oxidase activity was pH- and temperature-dependent, with a pH of 7.0 and the lowest temperature studied (32 degrees C) favoring the greatest pyruvate generation. Lactate was an unexpected by-product even though measured lactate dehydrogenase (LDH) activity was very low.
我们比较了六株大肠杆菌及其相应的ppc突变体中丙酮酸的积累情况。每株菌株都含有一个参与乙酸合成途径的基因突变。编码丙酮酸脱氢酶复合体的基因突变的菌株通常表现出最大程度的丙酮酸积累，其中对CGSC6162（一个aceF突变体）和CGSC6162 Delta ppc在受控发酵罐中进行了更详细的研究。在添加了乙酸盐的培养基中，CGSC6162和CGSC6162 Delta ppc积累的丙酮酸均大于35 g/l。我们观察到CGSC6162中葡萄糖生成丙酮酸的质量产率为0.72，体积产率高于1.5 g l⁻¹ h⁻¹。对于CGSC6162 Delta ppc，我们观察到丙酮酸产率为0.78，体积产率高于1.2 g l⁻¹ h⁻¹。CGSC6162消耗了所有最初供应的乙酸盐，而CGSC6162 Delta ppc在36小时的发酵过程中先消耗然后生成乙酸盐。乙酸盐的生成和丙酮酸氧化酶活性与pH和温度有关，pH为7.0且研究的最低温度（32℃）有利于产生最大量的丙酮酸。尽管测得的乳酸脱氢酶（LDH）活性非常低，但乳酸却是一种意外的副产物。
