초록
<P>It is increasingly attractive to engineer cyanobacteria for bulk production of chemicals from CO<SUB>2</SUB>. However, cofactor bias of cyanobacteria is different from bacteria that prefer NADH, which hampers cyanobacterial strain engineering. In this study, the key enzyme <SMALL>D</SMALL>-lactate dehydrogenase (LdhD) from <I>Lactobacillus bulgaricus</I> ATCC11842 was engineered to reverse its favored cofactor from NADH to NADPH. Then, the engineered enzyme was introduced into <I>Synechococcus elongatus</I> PCC7942 to construct an efficient light-driven system that produces <SMALL>D</SMALL>-lactic acid from CO<SUB>2</SUB>. Mutation of LdhD drove a fundamental shift in cofactor preference towards NADPH, and increased <SMALL>D</SMALL>-lactate productivity by over 3.6-fold. We further demonstrated that introduction of a lactic acid transporter and bubbling CO<SUB>2</SUB>-enriched air also enhanced <SMALL>D</SMALL>-lactate productivity. Using this combinational strategy, increased <SMALL>D</SMALL>-lactate concentration and productivity were achieved. The present strategy may also be used to engineer cyanobacteria for producing other useful chemicals.</P>