Autolysis of Lactobacillus sanfranciscensis

Autolysis of Lactobacilus sanfranciscensis in phosphate buffer was strain-d ependent and maximal in the exponential growth phase and at pH 5.6. It decr eased to 15% of the maximum at pH 4.5. In culture medium, autolysis did not correspond to the cell death rate because the low pH reached after ferment ation limited it markedly. Appreciable autolysis was only found when buffer ing citrate or fumarate were added to the culture medium. Leakage of peptid ases from cells to the culture medium confirmed the autolysis. Renaturating SDS-PAGE showed an autolytic profile composed of four clean lytic bands of ca. 102, 87, 76.5 and 61.5 kDa, This profile was observed in all strains a nd did not vary with the growth phase or with the use of the crude cell-env elope or crude extracts. Sourdough fermentations lasting 24-48 h showed no differences in the leakage of peptidases when strains which differed greatl y for autolysis were compared. However, if citrate was added to the dough i t enhanced the release of intracellular peptidases by fast autolytic strain s because of the less acidic conditions which favored microbial autolysis d uring sourdough fermentation.