Screening and Breeding of High-yield Strains for Acid α-Amylase by UV Mutagenesis

[Objective] Bacillus amyloliquefaciens 5 was used as initial strain for preparation of protoplast and UV-mutagenesis in order to promote its acid α-amylase production.[Method] The preparation rate of protoplast could reach 94% with 20 mg/ml of lysozyme by enzymolysising for 90 min at 37 ℃.The mutant with the bigger ratio of hydrolyzation circle diameter to bacterial colony diameter was screened after UV mutagenesis so as to assay acid α-amylase activities.[Result] Mutant UV-329 with acid α-amylase activity of 267 U/ml was screened from a lot of mutants,with an increase of 254.2% over that of the initial strain.[Conclusion] UV mutagenesis for protoplast was an effective breeding method.