The purification and activities of an alkaline protease of Aspergillus clavatus from Nigerian poultry feeds.

Optimal growth and extracellular protease production by Aspergillus clavatus Des. was recorded at 30 degrees C and between days 5 and 7 of the 8-day incubation period. Purification of this enzyme was achieved by a combination of ultrafiltration, alcoholic precipitation and fractionation on DEAE-cellulose and Sephadex-G.200. A single peak of an alkaline protease was subsequently obtained with a 9-fold increase in specific activity and a final recovery value of 26.2%. The enzyme had optimal activity at 37 degrees C and a pH of 7.8. The enzyme did not degrade leucine amide, hippurylphenylalanine and hippurylarginine indicating lack of exo-protease activity. However, endo-protease activity led to a rapid hydrolysis of gelatin with optimal activity at 40 degrees C and pH 7.8. The high incidence of A. clavatus on Nigerian poultry feeds vis-a-vis the potential health risks posed to farm animals is discussed.