Effect of Nitrogen Source on Freeze-dried Resistance of Lactobacillus delbrueckii subsp. bulgaricus B61-3

In this study, the utilization of 16 nitrogen sources of Lactobacillus delbrueckii subsp. bulgaricus B61-3 were determined, and the types and amounts of nitrogen sources that can improve the freeze-drying tolerance of the strain were screened out. More importantly, the effects of nitrogen source modification on the fermentation performance, cell morphology and enzyme activities of freeze-dried powder of the strain were investigated. The results showed that 30 g/L of bovine bone peptone improved the freeze-drying survival rate from 9.68% to 18.90%, and increased fermentation activity by 22.15% compared with the control group. Changed cell size and morphology of the cultured cells of bovine bone peptone were also observed by electron microscope. Cell cultured in bovine bone peptone medium represented a short rod with smooth surface, and the ratio of length to diameter or area to volume decreased significantly (P