초록
<P><I>Gluconobacter oxydans</I> is known to be a suitable candidate for producing xylitol from <SMALL>d</SMALL>-arabitol. In this study, the enzyme responsible for reducing <SMALL>d</SMALL>-xylulose to xylitol was purified from <I>G. oxydans</I> NH-10 and characterized as xylitol dehydrogenase. It has been reported that XDH depends exclusively on NAD<SUP>+</SUP>/NADH as cofactors with a relatively low activity, which was proposed to be the direct reason for its limiting the overall conversion process. To better produce xylitol, an engineered <I>G. oxydans</I> PXPG was constructed to coexpress the XDH gene and a cofactor regeneration enzyme (glucose dehydrogenase) gene from <I>Bacillus subtilis</I>. Activities for both enzymes were more than twofold higher in the <I>G. oxydans</I> PXPG than in the wild strain. Approximately 12.23 g/L xylitol was obtained from 30 g/L <SMALL>d</SMALL>-arabitol by resting cells of the engineered strain with a conversion yield of 40.8%, whereas only 7.56 g/L xylitol was produced by the wild strain with a yield of 25.2%. These results demonstrated that increasing the XDH activity and the cofactor NADH supply could improve the xylitol productivity notably.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jafcau/2013/jafcau.2013.61.issue-11/jf304983d/production/images/medium/jf-2012-04983d_0006.gif'></P>