. Five-microliter aliquots of each cell suspension at 108 CFU/ml were then inoculated on the plates,
which were incubated at 37oC for 5 d.
The proteolysis activity in the plates was visualized 24–48 h after staining with amido black solution
(amido black 0.5%, glacial acetic acid 49.5%, and distilled water 50%).2