Study on the screening high yield neutral-protease-producing strain by combing UV and nitrous acid mutagenesis

UV and HNO2 were successively used to promote the enzyme-activity of the neutral protease produced by a marine bacteria Exiguobacterium sp.SWJS2.Being directly exposed to 8W UV for 50 s with a vertical dimension of 20 cm,mutant strain UV-48 with a promotion of 21.32% were obtained after three turns of mutagenesis and then be applied into HNO2 mutagenesis for further promotion. Being diluted by 0.03 mol/L HNO2 for 8min,UV-48 was finally turned into HN-34 with a promotion of 13.97% than itself and 38.28% than the starting strain after three turns.After pass-generation tests for five times,the mutant strain HN-34 was proved to be genetically stable since the five relative enzyme-activity were all above 94%.