Issue 7, 2011

The direct conversion of xylan to lactic acid by Lactobacillus brevis transformed with a xylanase gene

Abstract

A xylanase gene (xynR8), obtained from the DNA of a pool of uncultured rumen microbes, was introduced via a plasmid into Lactobacillus brevis. 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−1) against oat-spelt xylan in broth when compared to the wild-type Lactobacillus brevisATCC367. 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 × 109 CFU ml−1 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−1 of lactic acid and 0.44 g l−1 of ethanol were present in the culture supernatant of the strain containing the recombinant xylanase. These results indicate that Lactobacillus brevis 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.

Graphical abstract: The direct conversion of xylan to lactic acid by Lactobacillus brevis transformed with a xylanase gene

Article information

Article type
Paper
Submitted
14 Feb 2011
Accepted
03 May 2011
First published
08 Jun 2011

Green Chem., 2011,13, 1729-1734

The direct conversion of xylan to lactic acid by Lactobacillus brevis transformed with a xylanase gene

C. Hu, D. Chi, S. Chen and Y. Chen, Green Chem., 2011, 13, 1729 DOI: 10.1039/C1GC15169J

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