Production and purification of acid protease from the thermophilic fungus, Penicillium duponti K1014.

A thermophilic fungus, Penicillium duponti K1014, produced an acid protease in a submerged culture. Maximum enzyme production, in a 30-liter fermentor at a preselected optimum growth temperature of 50 C, occurred after 3 days. The productivity of the enzyme was associated with changes of viscosity and pH of culture broth during the growth. The acid protease was isolated from the culture filtrates and was purified ninefold by alcohol precipitation, column chromatography on O-(diethylaminoethyl)cellulose, batchwise treatment with O-(carboxymethyl)cellulose, and by gel filtration. The purified enzyme was homogeneous on disk electrophoresis and sedimentation analysis. The sedimentation constant s(20.w), calculated at a concentration of 0.64%, was 3.98S.