초록
<P><B>Abstract</B></P> <P> <I>Propionibacterium freudenreichii</I> subsp. <I>shermanii</I> naturally forms propionic acid as the main fermentation product with acetate and succinate as two major by-products. In this study, overexpressing the native propionyl-CoA:succinate CoA transferase (CoAT) in <I>P. shermanii</I> was investigated to evaluate its effects on propionic acid fermentation with glucose, glycerol, and their mixtures as carbon source. In general, the mutant produced more propionic acid, with up to 10% increase in yield (0.62 vs. 0.56g/g) and 46% increase in productivity (0.41 vs. 0.28g/Lh), depending on the fermentation conditions. The mutant also produced less acetate and succinate, with the ratios of propionate to acetate (P/A) and succinate (P/S) in the final product increased 50% and 23%, respectively, in the co-fermentation of glucose/glycerol. Metabolic flux analysis elucidated that CoAT overexpression diverted more carbon fluxes toward propionic acid, resulting in higher propionic acid purity and a preference for glycerol over glucose as carbon source.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Propionyl-CoA:succinate CoA transferase (CoAT) was overexpressed in <I>P. shermanii</I>. </LI> <LI> More propionate and less acetate and succinate were produced by the mutant. </LI> <LI> Up to 10% increase in yield and 46% increase in productivity were obtained. </LI> <LI> CoAT overexpression also increased glycerol consumption and product purity. </LI> <LI> This is the first report on overexpressing CoAT for enhanced propionate production. </LI> </UL> </P>