Breeding of High-yield Alkaline Protease Producing Strain by Atmospheric and Room Temperature Plasma Mutagenesis

Abstract

To obtain alkaline protease producing strain with high-yield, the strain Bacillus subtilis was treated by atmospheric and room temperature plasma (ARTP) mutagenesis. The results showed that the strain had a higher positive mutation rate when the mutagenesis time was 50s. Finally, a high-yield mutant strain A59 was obtained after repeated mutagenesis by ARTP and enzyme activity increased by 23.38% from 6835U/mL to 8433U/mL. Then fermentation conditions of mutant strain were optimized by single-factor method and response surface method, and the optimum fermentation conditions were as follows: 3.6% soybean meal, 5.2% corn meal, 0.9115% Na2HPO4, 0.1593% Mg2+, 0.09% Tween-80 and 5% inoculation volume. Under the conditions of the verification experiment, the enzyme activity of the A59 strain reached 14026 U/mL, which was 2.05 times that of the original strain.