Abstract:[background] The Gram-negative Methylobacterium has the ability to grow in the low-carbon compound (such as methane, methanol, formaldehyde and so on) substrate with one carbon atom or no C−C bond, and synthesizes various metabolites such as amino acids, industrial enzymes, cofactors, polyhydroxyalkanoates (PHAs), polysaccharides, and carotenoids. [Objective] In this study, mutation of mutS gene in Methylobacterium sp. MB200 was performed, and targeted induction was conducted with stresses to yield mutant strains that can tolerate high concentration of methanol or formaldehyde. [Methods] The mutS deletion strain MB200sTB was constructed by triparental mating, and the concentration of methanol and formaldehyde in the culture medium was gradually increased to induce targeted mutations. Electrotransformation was used to yield complementary transformants. [Results] MB200sTB with mutS deletion was successfully constructed, and the methanol-tolerant MB200sHBc and formaldehyde-tolerant MB200sHBq were obtained. The methanol tolerance of MB200sHBc was greatly improved compared with that of the wild strain MB200. To be specific, the tolerant methanol concentration raised from 8 g/L to 44 g/L and the growth kept unchanged. In the presence of 0.45g/L formaldehyde as carbon source, the growth of MB200sHBq was 1.69 folds higher than that of MB200. [Conclusion] Through targeted induction of mutS deletion mutants, strains with high methanol tolerance and potential application prospect in production can be obtained.
