Study on ~(60)Coγ-Ray Irradiation Mutation of Bacillus subtils natto

摘要

Soybean meal (SBM) was widely used as raw material in plant protein industry. Bacillus subtilis natto was the beneficial bacteria of generating a variety of protease, which could degrade plant protein of SBM, so as to improve the hydrolysis degree (DH) of plant protein. Bacillus subtilis natto was commonly treated by ultraviolet ray(UV), Lithium chloride(LiCl), nitrosoguanidine (NTG), diethyl sulphate (DES) at home and abroad, but it had not been reported that bacillus natto was treated by ~(60)Coγ gamma rays (~(60)Coγ). Different dosages of ~(60)Coγ irradiation and 0.85 % Lithium chloride were used as mutagen in treating Bacillus subtils natto HRBX0. Result showed that when 400 Gy dosage was used, which led to a 95 % spore death rate with the positive mutation rate 14.5 %, good mutagenic effect occured. DH of defatted SBM in solid-state fermentation of the mutant HRBX6 increased from original 19.5 % to 30.6 %, increased by 56.9 %. It showed a good genetic stability and stably DH of defatted SBM with the experiments of the mutant after continuous cultivation for five generations and obviously exceeded the original strain. It showed that ~(60)Coγ was an effective factor of mutagenic breeding of Bacillus subtilis natto.