Polysaccharide degrading enzymes of a toxigenic strain of Aspergillus clavatus from Nigerian poultry feeds.

The factors responsible for the production and activities of polysaccharide degrading enzymes of a toxigenic strain of Aspergillus clavatus (ASC - IB 202) on an oat meal chaff (OMC) medium were studied. The enzymes assayed for were amylases, CM-cellulases, filter paper (FP)-cellulases, xylanases and dextranases. Amylase production by A. clavatus (ASC - IB 202) reached a peak within 48 h of incubation at 30 degrees C while optimal production of CM-cellulases occurred on day 6. The FP-cellulase and xylanase production did not reach a peak within the 10 day incubation period. Determination of dextranase activity showed optimal production and activity between days 6 and 8. When grown on varying sources of carbon at 30 degrees C, CM-cellulase production was only recorded on cellobiose, CM-cellulose and on the OMC medium. FP-cellulase production occurred on the microcrystalline cellulose and on the OMC medium. The other enzymes were produced to various extents on the carbon sources used. The best mycelial growth was recorded at 30 degrees C and pH 6.0. So also were the peak production of CM-cellulases and FP-cellulases. The xylanase and dextranase activity of the culture filtrate were optimally produced at 30 degrees C and pH 5.4. The potential health hazards which the presence of this toxigenic strain of Aspergillus clavatus on poultry feeds poses to farm animals including man are discussed.