Breeding Of Lactobacillus With High Lactic Acid Irradiated By Heavy Ion And The Optimization Of Fermentation Process

Lactobacillus is a kind of bacteria which could produce lactic acid by fermentation using glucose or lactose,it could provide the nutrition for human beings,regulate the formal flora in gastrointestinal tract keeping balance,and improve the immune capability.The ability to produce lactic acid is an important feature of lactic acid bacteria.The lactic acid high-production strain could shorten the fermentation time,enhance productivity,reduce production costs and improve economic performance compared with the original strain during the producing process.Therefore,screening the Lactobacillus with good performance and studying the growth characteristics of lactic acid bacteria have a great positive meaning for the industrial production of lactic acid bacteria products.So the object of this paper was that the Lactobacillus JT irradiated by heavy ion beam were screened by culture and through fermentation in test tube and acquire high-lactic acid produce mutant stain.And then,the ability of lactic acid high-production of mutant strain could be improved through the study of optimization of fermentation conditions.This research could provide a new strategy for strain breeding,and lay a theoretical foundation for the industrialization of the lactic acid bacteria application.The research studies were as follows:1.The result of original strain JT irradiated by heavy ion beam showed that a stable high-yield mutant strain,named JT10,which could produce 21.72 g/L of lactic acid with the yield increased by 43.65 %(P< 0.001)compared to the original strain(15.12 g/L).It was also proved that JT10 strain has good genetic stability by passage experiment.2.Through further screening 5 strains of mutant JT6,JT7,JT8,T9,JT10,finally be obtained.And by continuously 9 passages,the yield of lactic acid has good genetic stability,the highest yield of lactic acid acid producing strain JT10 is improved by 43.78% compared with the original strain(P < 0.001).3.The optimal culture conditions during the process of the fermentation were studied,the result showed that the optimal seed medium culture time is 16 h,the fermentation medium culture time is 22 h,inoculum dose is 5 %,initial pH value is 7 and the fermentation temperature is 37 ?.The result showed that the content of lactic acid of JT10 strain in optimal fermentation(24.07 g/L)was 10.82%(P < 0.01)higher than the mutant strain JT10 in original fermentation(21.72 g/L).This research established the screening method of the breeding of Lactic acid high-yieldstrains after being irradiated by heavy ion beam.Using this method,a mutant strain JT10 was selected.And via the optimization of fermentation conditions,the mutant strain JT10 was59.19 % higher yield of lactic acid than original strain JT.