Mutation Breeding of a β-Mannanase-producing Endophytic Bacteria and its Enzymatic Characterization
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Abstract:
The mutagenic effects of the ultraviolet ray, diethyl sulfate's single factor and ultraviolet-diethyl sulfate compound mutagenesis on Bacillus subtilis HD-1 (54.6 U/mL) were studied. Results of enzyme activity showed that ultraviolet-diethyl sulfate compound mutagenesis was better. A mutant strain, named Bacillus subtilis UD-20 with high-level β-mannanase production was obtained after ultraviolet-diethyl sulfate compound mutagenesis from Bacillus subtilis HD-1 which was an endophytic bacteria screened from soybean seeds. The β-mannanase activity of Bacillus subtilis UD-20 increased 63.9% compared with that of the original strain Bacillus subtilis HD-1 (54.6 U/ml) and was stable during the generations. The optimal temperature for β-mannanase activity was 50 ℃ and the enzyme was stable up to 50 ℃. The optimal pH for enzyme activity was 7.0 and the enzyme demonstrated broad pH stability within a pH range of 5.0~8.0. The β-mannanase activity was activated by Fe2+ (113.2%) and Co2+ (131.7%), but strongly inhibited by Mn2+ (55.6%). The β-mannanase stability was increased by K+, Ca2+, Ba2+, among which Co2+ (150%) showed the best effect on the enzyme stability.
