Purification and characterization of phytase from Aspergillus fumigatus Isolated from African Giant Snail (Achatina fulica)

Phytase, an enzyme that catalyzes the stepwise hydrolysis of phytate into phosphorous and organophosphate compound and capable of reducing environmental pollution and metal chelating effect of phytate was purified from Aspergillus fumigatus isolated from African Giant Snail (Achatina fulica). The crude phytase was subjected to ammonium sulphate precipitation, DEAE Sephacel and Sephacryl S-200. Physicochemical parameters of the enzyme were investigated. Approximately 45%-fold purification was achieved with an overall recovery of 15%. The purified phytase had optima temperature and pH activity at 40 degrees C and pH 6 respectively with a marked activity of 83% and 78% at pH 8.0 and 9.0 respectively. It retained over 80% of its initial activity after 6 h at pH 4.0 - 7.0 with a 48% remaining activity at 50 degrees C after 1 h incubation time. Vmax and Km were determined to be 35.7 mu mol/min and 7.2 mM respectively. The phytase activity was enhanced in the presence of Ca2+, Cu2+ and Fe2+, but was greatly inhibited by Zn2+, Hg2+, Al3+, sodium dodecyl sulphate (SDS) and urea. The results showed that phytase produced from A. fumigatus may contribute significantly to the phytate degrading enzyme system in African giant snail and may serve a useful commercial purpose.