Production and selection of mutants of Leuconostoc mesenteroides constitutive for glucansucrases.

After chemical mutagenesis using ethyl methane sulfonate, we isolated mutants constitutive for glucansucrases from Leuconostoc mesenteroides NRRL B-512FM, B-1142, and B-1355. Those mutants produced glucansucrases when grown on D-glucose as well as on sucrose. They produced higher glucansucrase activities (3 to 22 times) when grown on D-glucose than the parent strains grown on sucrose. Glucansucrases from mutants B-1355C and B-1142C grown on glucose formed glucans that were highly resistant to Penicillium dextranase hydrolysis. Mutant B-512FMC dextransucrase formed the same kind of dextran as the parent strain; however, it showed higher thermal stability, even when dextran was absent.