Evaluation of chromogenic substrates for measurement of protease production by biocontrol strains of Trichoderma.

Four chromogenic substrates were compared, and methods were developed for measuring protease activity from fungi. Digestion of azoalbumin, a water-soluble substrate, resulted in dye release most closely proportional to enzyme activity. Substrates insoluble in water were advantageous for time-course studies, and azocoll was more sensitive to digestion and easier to handle than hide powder azure. The optimal pH was 7 for measurement of extracellular protease activity from the Trichoderma strains. Addition of calcium or serine protease inhibitors did not affect crude protease activity. The optimized protocol was used to demonstrate that specific activity of proteases produced by the strains of Trichoderma tested did not correlate with their known biocontrol ability.