초록
<P>A xylanase gene (<I>xyn</I>R8), obtained from the DNA of a pool of uncultured rumen microbes, was introduced <I>via</I> a plasmid into <I>Lactobacillus brevis</I>. The recombinant xylanase, with an estimated molecular weight of 32 KDa, was expressed in the transformants and showed obvious xylanase activity (0.412 U ml<SUP>−1</SUP>) against oat-spelt xylan in broth when compared to the wild-type <I>Lactobacillus brevis</I> ATCC367. The transformants all shared a similar ability to utilize and metabolize xylooligosaccharides. When a selected transformant was inoculated into modified MRS medium containing xylan as the main carbon source, the cell density reached 2.20 × 10<SUP>9</SUP> CFU ml<SUP>−1</SUP> on day 4, while the wild-type strain without the plasmid containing the recombinant xylanase did not grow at all under the same conditions. After fermentation, 1.70 g l<SUP>−1</SUP> of lactic acid and 0.44 g l<SUP>−1</SUP> of ethanol were present in the culture supernatant of the strain containing the recombinant xylanase. These results indicate that <I>Lactobacillus brevis</I> containing the xylanase gene is capable of directly saccharifying and fermenting xylan to produce lactic acid in one step. This strain will enable the development of a feasible and economical approach to the production of lactic acid directly from xylan.</P> <P>Graphic Abstract</P><P><I>Lactobacillus brevis</I> containing the xylanase gene is capable of directly saccharifying and fermenting xylan to produce lactic acid in one step. This strain will enable the development of a feasible and economical approach to the production of lactic acid directly from xylan.<BR><IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1gc15169j'><BR></P>