초록
<P><I>Clostridium cellulovorans</I> DSM 743B can produce butyrate when grown on lignocellulose, but it can hardly synthesize butanol. In a previous study, <I>C. cellulovorans</I> was successfully engineered to switch the metabolism from butyryl-CoA to butanol by overexpressing an alcohol aldehyde dehydrogenase gene <I>adhE1</I> from <I>Clostridium acetobutylicum</I> ATCC 824; however, its full potential in butanol production is still unexplored. In the study, a metabolic engineering approach based on a push-pull strategy was developed to further enhance cellulosic butanol production. In order to accomplish this, the carbon flux from acetyl-CoA to butyryl-CoA was pulled by overexpressing a trans-enoyl-coenzyme A reductase gene (<I>ter</I>), which can irreversibly catalyze crotonyl-CoA to butyryl-CoA. Then an acid reassimilation pathway uncoupled with acetone production was introduced to redirect the carbon flow from butyrate and acetate toward butyryl-CoA. Finally, xylose metabolism engineering was implemented by inactivating <I>xylR</I> (<I>Clocel_0594</I>) and <I>araR</I> (<I>Clocel_1253</I>), as well as overexpressing <I>xylT</I> (<I>CA_C1345</I>), which is expected to supply additional carbon and reducing power for CoA and butanol synthesis pathways. The final engineered strain produced 4.96 g/L of <I>n</I>-butanol from alkali extracted corn cobs (AECC), increasing by 235-fold compared to that of the wild type. It serves as a promising butanol producer by consolidated bioprocessing.</P><BR>[FIG OMISSION]</BR>