초록
<P><B>Background</B></P><P>Current methods of ethanol production from lignocelluloses generate a mixture of sugars, primarily glucose and xylose; the fermentation cells are always exposed to stresses like high temperature and low nutritional conditions that affect their growth and productivity. Stress-tolerant strains capable of using both glucose and xylose to produce ethanol with high yield are highly desirable.</P><P><B>Results</B></P><P>A recombinant <I>Zymomonas mobilis</I> (<I>Z. mobilis)</I> designated as <I>HYMX</I> was constructed by integrating seven genes (<I>Pfu-sHSP, yfdZ, metB, xylA, xylB, tktA</I> and <I>talB</I>) into the genome of <I>Z. mobilis</I> CP4 <I>(CP4)</I> via Tn5 transposon in the present study. The small heat shock protein gene (<I>Pfu-sHSP</I>) from <I>Pyrococcus furious</I> (<I>P. furious</I>) was used to increase the heat-tolerance, the <I>yfdZ</I> and <I>metB</I> genes from <I>E. coli</I> were used to decrease the nutritional requirement. To overcome the bottleneck of <I>CP4</I> being unable to use pentose, xylose catabolic genes (<I>xylA, xylB, tktA</I> and <I>talB</I>) from <I>E. coli</I> were integrated into <I>CP4</I> also for construction of the xylose utilizing metabolic pathway.</P><P><B>Conclusions</B></P><P>The genomic integration confers on <I>Z. mobilis</I> the ability to grow in medium containing xylose as the only carbon source, and to grow in simple chemical defined medium without addition of amino acid. The <I>HYMX</I> demonstrated not only the high tolerance to unfavorable stresses like high temperature and low nutrient, but also the capability of converting both glucose and xylose to ethanol with high yield at high temperature. What’s more, these genetic characteristics were stable up to 100 generations on nonselective medium. Although significant improvements were achieved, yeast extract is needed for ethanol production.</P>