The activities of partially purified acid proteases of thermotolerant Aspergillus species from post harvest oil palm kernels

Abstract

AbstractThe production and activities of extracellular acid proteases of Aspergillus fumigatus Fres and Aspergillus nidulans (Eidam) Wint were studied. Both species grew readily on the palm kernel oil‐peptone medium resulting in peak protease production and biomass accumulation occurring within the incubation period of 10 dys. Partial purification of the crude protease from the culture filtrate of A. fumigatus on DEAE‐cellulose and on Sephadex G‐200 gave a single active protease peak being eluted with thF protein front at A280‐A 47‐fold purification was achieved with a recovery value of 2.1 %. The specific activity (22.4 U/mg protein) of A. fumigatus protease was much higher than that of A. nidulans protease (11.4 U/mg protein). Also, A. fumigatus protease was most active at 40 °C and pH 5.8 on casein and on gelatin. A. nidulans protease acted best at 45 °C and pH 5.4 on similar substrate. The proteases from both fungi showed no exoprotease activity when used to hydrolyze leucine amide, hippuryl phenylalanine and hippuryl arginine.