Breeding study of Lactobacillus Thermophilics induced by X- ray for L- lactic acid production

In order to obtain a lactic acid bacteria strain to more suitable for industrial production and to improve the production efficiency. The Lactobacillus thermophilus which irradiated by X- ray were screened by calcium carbonate- bromocresol purple plate and submerged fermentation in shaking flask. The results showed that a stable high- yield mutant strain,named SR7,could produce 22 g / L of L- lactic acid on average with the yield increase of 15.04%,compared to the original strain.It was also proved that SR7 strain had good genetic stability by repeating experiments.