초록
<P><B>Background</B></P><P>Production of L-sorbose from D-sorbitol by <I>Gluconobacter oxydans</I> is the first step to produce L-ascorbic acid on industrial scale. The <I>sldhAB</I> gene, which encodes the sorbitol dehydrogenase (SLDH), was overexpressed in an industrial strain <I>G. oxydans</I> WSH-003 with a strong promoter, <I>P</I><SUB><I>tufB</I></SUB>. To enhance the mRNA abundance, a series of artificial poly(A/T) tails were added to the 3′-terminal of <I>sldhAB</I> gene. Besides, their role in <I>sldhAB</I> overexpression and their subsequent effects on L-sorbose production were investigated.</P><P><B>Results</B></P><P>The mRNA abundance of the <I>sldhAB</I> gene could be enhanced in <I>G. oxydans</I> by suitable poly(A/T) tails. By self-overexpressing the <I>sldhAB</I> gene in <I>G. oxydans</I> WSH-003 with an optimal poly(A/T) tail under the constitutive promoter <I>P</I><SUB><I>tufB</I></SUB>, the titer and the productivity of L-sorbose were enhanced by 36.3% and 25.0%, respectively, in a 1-L fermenter. Immobilization of <I>G. oxydans</I>-sldhAB6 cells further improved the L-sorbose titer by 33.7% after 20 days of semi-continuous fed-batch fermentation.</P><P><B>Conclusions</B></P><P>The artificial poly(A/T) tails could significantly enhance the mRNA abundance of the <I>sldhAB</I>. Immobilized <I>G. oxydans</I>-sldhAB6 cells could further enlarge the positive effect caused by enhanced mRNA abundance of the <I>sldhAB</I>.</P>