Ammar Ehab Mohamed, Jin Ying, Wang Zhongqiang, Yang Shang-Tian
William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 140 West 19th Avenue, Columbus, OH, 43210, USA.
Appl Microbiol Biotechnol. 2014 Sep;98(18):7761-72. doi: 10.1007/s00253-014-5836-y. Epub 2014 May 31.
Propionic acid is currently produced mainly via petrochemicals, but there is increasing interest in its fermentative production from renewable biomass. However, the current propionic acid fermentation process suffers from low product yield and productivity. In this work, the gene encoding phosphoenolpyruvate carboxylase (PPC) was cloned from Escherichia coli and expressed in Propionibacterium freudenreichii. PPC catalyzes the conversion of phosphoenolpyruvate to oxaloacetate with the fixation of one CO2. Its expression in P. freudenreichii showed profound effects on propionic acid fermentation. Compared to the wild type, the mutant expressing the ppc gene grew significantly faster, consumed more glycerol, and produced propionate to a higher final titer at a faster rate. The mutant also produced significantly more propionate from glucose under elevated CO2 partial pressure. These effects could be attributed to increased CO2 fixation and resulting changes in the flux distributions in the dicarboxylic acid pathway.
丙酸目前主要通过石化产品生产，但利用可再生生物质进行发酵生产的兴趣日益浓厚。然而，目前的丙酸发酵过程存在产品产量和生产率较低的问题。在这项工作中，编码磷酸烯醇丙酮酸羧化酶（PPC）的基因从大肠杆菌中克隆出来，并在费氏丙酸杆菌中表达。PPC催化磷酸烯醇丙酮酸转化为草酰乙酸，并固定一个二氧化碳。它在费氏丙酸杆菌中的表达对丙酸发酵产生了深远影响。与野生型相比，表达ppc基因的突变体生长明显更快，消耗更多甘油，并以更快的速度产生更高终浓度的丙酸盐。在升高的二氧化碳分压下，该突变体从葡萄糖中产生的丙酸盐也显著更多。这些影响可归因于二氧化碳固定增加以及二羧酸途径中通量分布的变化。
