Mutation and Optimization of Culture Conditions of Ammonia-degrading Bacteria in Mariculture Affluent

High-yield strains YS5,YW5 and YL3 were developed from original bacteria—ZS7,ZW38 and ZL5 mutagenized by a microwave and NTG.The mutant strain YS5 had enzyme activity of 2.471×103 U/ml,increasing by almost 2.2 times at the condition of pH 6.8~8.0,and temperature of 37 ℃.The YW5 and YL3 were found to increase in generation rate of nitrite almost by 1.5 times and 1.7 times of 3.39 mg/(L·d) for YW5 and 3.05 mg/(L·d) for YL3.