Glycine betaine transport conditions of Lactobacillus delbrueckii subsp. bulgaricus in salt induced hyperosmotic stress

Glycine betaine (GB) is a naturally occurring osmolyte that helps cells adapt to osmotic stress. In this study, the osmoprotective role of GB in Lactobacillus delbrueckii subsp. bulgaricus 34.5 under salt stress was investigated. A concentration of 0.2 m NaCl provided sufficient osmotic constraint while allowing the cells to survive. Under conditions of salt stress, Lactobacillus bulgaricus 34.5 continued to proliferate in the presence of GB, and the optimum growth was seen at 1.2 mm GB. The optimum culture conditions for L. bulgaricus 34.5 were 37 °C and pH 6.0 for 24 h. In addition, intracellular GB content increased in response to salt stress, and the extent of GB transport in L. bulgaricus 34.5 under high salt concentrations depended on the culture conditions. In conclusion, GB played a protective role in alleviating the detrimental effect of salt on L. bulgaricus 34.5.