Breeding of Lactic Acid High Producing Bacillus UZ-3-15 by UV Mutation

In order to obtain lactic acid high producing strains,the study used Bacillus Z-3-1 which was obtained before as original strain for stepwise mutation by UV irradiation was carried out.Conditions for mutagenesis were 30 W UV lamp,30 cm irradiation distance and irradiation dose of 150 s.In the experiment,the preliminary screening of mutant strains was implemented first through calcium-dissolving,and 19 strains with bigger transparent circle diameters in the MRS-CaCO3 medium were obtained in the preliminary screening.Then the secondary screening of 19 strains was done,and one lactic acid high producing strain named UZ-3-15 was obtained by the titration method for determination of lactic acid in the fermented broth,which produced 7 times more lactic acid than its parent strain in the NB medium.