Production of Xylanase from Aspergillus sydowii Isolated from Irvingia gabonensis (African Mango) Fruit

This work reports xylanase production from Aspergillus sydowii isolated from spoiled Irvingia gabonensis fruit. Selection of the fungus was based on the production of maximum zone of clearing on agar containing 5% beech wood xylan. The influence of pure carbon substrates on enzyme production showed that the medium containing mannitol produced a maximum enzyme yield of 50.1 U/mg protein after incubation for 72 h. Enzyme productivity in this medium was much higher in a medium that contained only xylan (44.9 U/mg protein) as the sole carbon source. Nitrogen sources were tested for their abilities to stimulate enzyme production and the best enzyme production was observed in the medium containing peptone caused the production of specific enzyme activity of 41.2 U/mg protein after 72 h. The enzyme showed maximum activity (55 U/mg protein) at pH 4.0 and optimum stability at pH 3.0-5.0. Temperature activity profile of the enzyme showed best activity (68 U/mg protein) at 35oC. Best temperature stability occurred at 30-40oC. Dried agricultural residues were tested for their abilities to support xylanase production in media devoid of xylan. The overall best enzyme productivities of 97.8 and 92.6 U/mg protein were achieved after 72 h in the medium containing orange peel and mango peel respectively. These levels were much higher than that achieved when pure carbon sources or xylan alone were used for enzyme production.

 O. Nwokoro, S. G. Uwa