A Novel Method for the Detection of Protease and the Development of Extracellular Protease in Early Growth Stages of Lactobacillus delbrueckii ssp. bulgaricus

A novel method of rapid detection using microplate wells with casein and calcium ions was developed for measuring protease activity. This new method is based on the theory that the hydrolysis by the proteases reduces the turbidity of the solution without coagulation. The three Lactobacillus delbrueckii ssp. bulgaricus strains that were tested secreted a protease with activity that reached its maximum 4 to 8 h after incubation (log phase) and then decreased rapidly. The new method allows the protease activity to be detected and measured more rapidly, easily, and economically than do other methods with fluorescent reagents or radioisotopes, and the new method is especially useful for analyzing large numbers of test samples (e.g., chromatographically fractionated eluates).