초록
<P><B>Abstract</B></P> <P> <I>Klebsiella oxytoca</I> KMS005 (∆<I>adhE</I>∆<I>ackA</I>-<I>pta</I>∆<I>ldhA</I>) was metabolically engineered to improve 2,3-butanediol (BDO) yield. Elimination of alcohol dehydrogenase E (<I>adhE</I>), acetate kinase A-phosphotransacetylase (<I>ackA-pta</I>), and lactate dehydrogenase A (<I>ldhA</I>) enzymes allowed BDO production as a primary pathway for NADH re-oxidation, and significantly reduced by-products. KMS005 was screened for the efficient glucose utilization by metabolic evolution. KMS005-73T improved BDO production at a concentration of 23.5±0.5g/L with yield of 0.46±0.02g/g in mineral salts medium containing 50g/L glucose in a shake flask. KMS005-73T also exhibited BDO yields of about 0.40–0.42g/g from sugarcane molasses, cassava starch, and maltodextrin. During fed-batch fermentation, KMS005-73T produced BDO at a concentration, yield, and overall and specific productivities of 117.4±4.5g/L, 0.49±0.02g/g, 1.20±0.05g/Lh, and 27.2±1.1g/gCDW, respectively. No acetoin, lactate, and formate were detected, and only trace amounts of acetate and ethanol were formed. The strain also produced the least by-products and the highest BDO yield among other <I>Klebsiella</I> strains previously developed.</P> <P><B>Highlight</B></P> <P> <UL> <LI> <I>K. oxytoca</I> KMS005-73T (∆<I>adhE</I>∆<I>ackA-pta</I>∆<I>ldhA</I>) improved BDO yield (up to 0.49g/g). </LI> <LI> Only acetate and ethanol (<2.5g/L in total) as by-products were detected. </LI> <LI> The fermentation was performed in low salt medium thus lowering BDO production cost. </LI> <LI> The costs of downstream processing and waste disposal would be also decreased. </LI> </UL> </P>