Abstract: Lactobacillus brevis NCL912 is aγ-aminobutyric acid-producing strain isolated from fermented vegetables. In the present study, protein expression in Lb. brevis NCL912 was investigated at the proteomic level and the effect of sodium L-glutamate (L-MSG) on protein expression was also explored under acid stress by two-dimensional gel electrophoresis, mass spectroscopy and bioinformatics. Eleven spots of 26 differential expressed proteins from the culture with L-MSG and 8 spots of 25 proteins from the culture without L-MSG were identified. The results showed that Lb. brevis NCL912 might launch the common acid resistance systems such as protein synthesis, glycometabolism and stress proteins to protect the cells against acid stress, which was irrelevant to L-glutamate. Meanwhile, exogenous amino acids might change the expression of some of the proteins which were involved in cell membrane formation and signal transduction in media with L-glutamate, thus benefiting the survival and growth of the cells. Therefore, the acid resistance-responsive system is a very complex network system, which is related to not only exogenous amino acids, but also the expression of bacterial proteins.

Key words: Lactobacillus brevis NCL912, sodium L-glutamate, proteomics, acid stress