초록
<P>Malic acid is mainly used as an acidulant and taste enhancer in the beverage and food industry. Previously, a mutant strain <I>Thermobifida fusca</I> muC, obtained by adaptive evolution was found to accumulate malic acid on cellulose with low yield. In this study, the malic acid synthesis pathway in <I>T. fusca</I> muC was confirmed to be from phosphoenolpyruvate to oxaloacetate, followed by reduction of oxaloacetate to malate. To increase the yield of malic acid by the muC strain significantly, the carbon flux from pyruvate was redirected to oxaloacetate by expressing an exogenous pyruvate carboxylase (PCx) gene from <I>Corynebacterium glutamicum</I> ATCC 13032 in the chromosome of <I>T. fusca</I> muC‐16. The yield of malic acid in the engineered strain muC‐16 was increased by 47.9% compared to the parent strain muC. The muC‐16 strain was then grown on ∼100 g/L cellulose and the highest titer of malic acid was 62.76 g/L by batch fermentation. <I>T. fusca</I> muC‐16 strain converted milled corn stover to malic acid with the highest titer of 21.47 g/L with minimal treatment. © 2016 American Institute of Chemical Engineers <I>Biotechnol. Prog.</I>, 32:14–20, 2016</P>