Screening of strains producing nuclease P1 by compound mutation of LiCl and ion beam

For meeting the needs of high-yield industrial production strains of nuclease P1,use LiCl and ion beam mutation ways to do research on Penicillium citrinum.The mutation conditions were optimized by fatality rate and positive mutation rate.The optimum mutation concentration of LiCl is 1.4%,the optimal fl uence of ion beam is 10 keV,1.5×1015 ions/cm2.Then the two ways were combined to do compound mutation,one high-yield mutant L-I-4-f was obtained.The enzyme activity of the strain is 1166 U/mL,which is nearly 45.8% highter than the original strain d-3-12.Several passages and separation experiments show that the heredity of mutants was stable.