Hydrolysis of vegetable oils and triglycerides by thermotolerant and zoopathogenic species of Aspergillus from Nigerian palm produce.

The ability of Aspergillus fumigatus Fres. and Aspergillus nidulans (Eidam) Wint obtained from Nigerian palm produce to degrade vegetable oils and triglycerides and the production and activity of their extracellular lipases were studied. Both species readily hydrolysed palm oil and palm kernel oil among others liberating free fatty acids in the process. Good growth with mycelia production of both fungi were also recorded on the triglycerides used as sources of carbon at 37 degrees C with the best results obtained on palmitic and oleic acids, the predominant fatty acids in palm oil. Extracellular lipases were detected in the culture filtrates of both fungi within 48 h of incubation on an oat-meal chaff medium at 37 degrees C. Peak enzyme production occurred within the 10-day incubation period. The lipases of both fungal species were most active at a pH of 5.6 and a temperature of 45 degrees C. The best glyceride for assaying the lipase activities of these fungi was trihexanoin while palm oil was a better vegetable oil than the conventional groundnut oil used for the same purpose. Because of the zoopathogenic nature of these fungi, attention is drawn to the potential health risks which their presence on the palm products where they were obtained pose to the consumers.