Effect of environmental conditions on the productivity and activity of proteases from aspergillus niger and aspergillus terreus grown on whey

ABSTRACT

Nine-day old culture of A. niger and A. terreus achieved the maximum yield of proteases in response to initial pH 5.25 and 6.15, respectively. Maximum activity was recorded at pH 8 for alkaline proteases from both fungi whereas acid protease from A. niger expressed maximum activity at pH 5. Alkaline proteases from A. niger and A. terreus expressed 2 pKa values at pH 6.1 or 8.9 and pH 7.0 or 8.7, respectively; while, acid protease from A. niger exhibited these values at pH 4.2 and 6.6. Phosphate buffer at 0.02-0.1 M favored the accumulation of the enzyme in the culture of A. niger, a phenomenon that was observed with A. terreus at 0.01 M or in the absence of phosphate buffer. The temperature optima for the formation of proteases were 25 and 28C for A. niger and A. terreus, respectively. However, the biosynthesis of proteases was always associated with the growth of both fungi. Temperature optima were 50, 40 and 40C for alkaline proteases from A. niger and A. terreus and acid protease from A. niger, respectively. Activation energies were 17.0, 6.9 and 12.6 kJ mol-1 for the above-mentioned enzymes in the same sequence indicating that protease from different Aspergilli or even from the same individual have different properties