초록
<P><B>Abstract</B></P> <P>This study investigated the effect of the methylmalonyl-CoA carboxyltransferase (MMC) of <I>Propionibacterium freudenreichii</I> on production of free fatty acid (FFA) in <I>Escherichia coli</I>. Overexpression of the MMC exhibited a 44% increase in FFA titer. Co-overexpression of MMC and phosphoenolpyruvate carboxylase (PPC), which supplies the MMC precursor, further improved the titer by 40%. Expression of malic enzyme (MaeB) led to a 23% increase in FFA titer in the acetyl-CoA carboxylase (ACC)-overexpressing cells, but no increase in the MMC-overexpressing cells. The highest FFA production in the MMC-overexpressing strain was achieved through the addition of aspartic acid, which can be converted into oxaloacetate (OAA), resulting in a 120% increased titer compared with that in the ACC-overexpressing strain. These findings demonstrate that MMC provides an alternative pathway for malonyl-CoA synthesis and increases fatty acid production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Methylmalonyl-CoA carboxyltransferase (MMC) bypass was introduced in <I>E. coli</I>. </LI> <LI> MMC bypass provides an alternative route for malonyl-CoA synthesis. </LI> <LI> MMC bypass alters precursor specificity for malonyl-CoA synthesis. </LI> <LI> MMC redirects carbon flux from the TCA cycle to FFA synthesis during bypass. </LI> <LI> Increasing precursor availability led to a 2.5-fold increase in FFA production. </LI> </UL> </P>