earticle

영어

Mannheimia succiniciproducens MBEL55E, a capnophilic rumen bacterium, produces succinic
acid in high concentrations as a fermentation end product under anaerobic conditions. In this
study we quantitatively investigated the response of Mannheimia succiniciproducens MBEL55E to different levels of dissolved CO2 ranging from 0 to 260 mM. The cells could not grow below 8.74 mM of dissolved CO2, indicating that there is a threshold level of CO2 to sustain the growth of M. succiniciproducens. 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). The results provide useful information for the design of effective bioprocesses by maximizing CO2 availability and also for the rational metabolic engineering by optimizing metabolic fluxes to improve succinic acid production[This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MOST) (2005-01294). Further supports by the LG Chem Chair Professorship, IBM SUR program, Microsoft, and by the KOSEF through the Center for Ultramicrochemical Process Systems are appreciated.].