Saccharide production from methanol by transposon 5 mutants derived from the extracellular polysaccharide-producing bacterium Methylobacillus sp strain 12S

A CH3OH-utilizing bacterium that has the ability to produce extracellular polysaccharide (EPS) was isolated from a soil sample, and was identified as the obligate methylotroph Methylobacillus sp. strain 12S on the basis of its 16S. rDNA sequence and growth-substrate specificity. The EPS produced by strain 12S was purified and the sugar composition was analysed by CC-MS and HPLC to reveal that the EPS was a heteropolymer composed of glucosyl, galactosyl, and mannosyl residues in the molar ratio 3:1:1. In order to produce mono- and/or oligosaccharides by single-step fermentation from CH3OH, stain 12S was mutagenized by transposon 5. Among eleven EPS-deficient mutants, three strains were found to accumulate significant amounts of reducing sugars in the media. The amounts of the reducing sugars produced by the mutants (> ca. 700 mg glucose equivalent/l) were >11-22 times higher than those produced by the wild-type strain (<ca. 60 mg glucose equivalent/l). The CC-MS analysis showed that all the mutants accumulated glucose, erythrose, threose and a disaccharide-like compound in the media.