Proteomic analysis of the response to NaCl stress of Lactobacillus bulgaricus.

Lactobacillus bulgaricus is commonly used in dairy products as a starter culture. Its viability during freeze-drying is of commercial interest. Here a significant (p < 0.05) improvement in survival rate of L. bulgaricus ATCC 11842 was achieved during freeze-drying when it was prestressed with 2 % (w/v) NaCl for 2 h in the late growth phase. To understand the mechanism of this stress-related viability improvement in L. bulgaricus, protein synthesis was analyzed by 2D difference gel electrophoresis. Nine protein spots were significantly altered by NaCl and were subsequently identified by peptide mass fingerprinting. The functions of the proteins included stress-related protein synthesis, amino acid biosynthesis, nucleotide biosynthesis, sugar metabolism, transport systems, and vitamin biosynthesis. These findings provide a considerable background regarding the NaCl stress response of L. bulgaricus.