Assessment of Dissolved CO2 Levels on Growth, Succinic Acid Production, and Enzyme Activities of Mannheimia succiniciproducens MBEL55E

Abstract

Mannheimia succiniciproducens MBEL55E produces succinic acid in high concentrations. we quantitatively investigated the response of Mannheimia succiniciproducens MBEL55E to different levels of dissolved CO2 ranging from 0 to 260 mM. Yields for biomass and succinic acid on glucose were 1.49 and 1.52 times higher at 141 mM CO2 than those obtained from 8.74 mM CO2, respectively. Comparing the fermentation results with the levels of key enzyme activities, we found that the efficient carboxylation of phosphoenolpyruvate (PEP) to oxaloacetate, in which CO2-fixation occurs by both PEP carboxykinase (PckA) and PEP carboxylase (Ppc), allows M. succiniciproducens to produce substantial amounts of succinic acid. In particular, the activity of PckA was more than 50 times higher than those of Ppc and malic enzyme (SfcA).