초록
<P><B>Abstract</B></P> <P>The efficient fermentative production of solvents (acetone, <I>n</I>-butanol, and ethanol) from a lignocellulosic feedstock using a single process microorganism has yet to be demonstrated. Herein, we developed a consolidated bioprocessing (CBP) based on a twin-clostridial consortium composed of <I>Clostridium cellulovorans</I> and <I>Clostridium beijerinckii</I> capable of producing cellulosic butanol from alkali-extracted, deshelled corn cobs (AECC). To accomplish this a genetic system was developed for <I>C. cellulovorans</I> and used to knock out the genes encoding acetate kinase (<I>Clocel_1892</I>) and lactate dehydrogenase (<I>Clocel_1533</I>), and to overexpress the gene encoding butyrate kinase (<I>Clocel_3674</I>), thereby pulling carbon flux towards butyrate production. In parallel, to enhance ethanol production, the expression of a putative hydrogenase gene (<I>Clocel_2243</I>) was down-regulated using CRISPR interference (CRISPRi). Simultaneously, genes involved in organic acids reassimilation (<I>ctfAB, cbei_3833/3834</I>) and pentose utilization (<I>xylR, cbei_2385</I> and <I>xylT, cbei_0109</I>) were engineered in <I>C. beijerinckii</I> to enhance solvent production. The engineered twin-clostridia consortium was shown to decompose 83.2g/L of AECC and produce 22.1g/L of solvents (4.25g/L acetone, 11.5g/L butanol and 6.37g/L ethanol). This titer of acetone-butanol-ethanol (ABE) approximates to that achieved from a starchy feedstock. The developed twin-clostridial consortium serves as a promising platform for ABE fermentation from lignocellulose by CBP.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An improved genetic system was developed for <I>Clostridium cellulovorans</I> DSM 743B. </LI> <LI> CRISPRi was shown to be an efficient tool for down-regulation of the expression of putative essential genes in <I>Clostridium</I>. </LI> <LI> The engineered consortium of <I>C. cellulovorans</I> DSM 743B and <I>C. beijerinckii</I> NCIMB 8052 produced 22.1g/L solvent by CBP. </LI> </UL> </P>