Purification and Characterization of Phytase from Fruit Bodies of Local mushroom Pleorotus ostreatus Grown by Solid State Fermentation

Abstract

Phytase produced from an edible local mushroom P.ostreatus11L was purified in three steps, in precipitation with ammonium Sulfate (saturation ratio70%), the specific activity of phytase increased from 0.38u/mg protein in crude extract to 0.77 u/mg protein with purification of 2.03 fold and  the enzyme yield was 92.05%, in ion exchange chromatography(DEAE-cellulose) step, specific activity was 3.6 u/mg protein with purification of 9.47 fold  with a yield of 71. 82%. In the last step, with gel filtration chromatography using Sephadex G75 which gave the highest specific activity reached 7.5 U/mg with the purification folds arrived to 19.74 and enzyme yield was 42.61%. The results showed that there is only one band appeared in SDS-PAGE technique indicating a high purity of phytase enzyme , the purified phytase behaved as a monomeric protein with a molecular mass of about 25.12 kDa . The phytase was active over a broad range of incubation temperature (20 - 50ºC), maximal activity was 0.83 unit/ml when phytase incubated at 30ºC while the enzyme has thermal stability over a broad range of temperatures (20-60ºC) for one h since more than 50 % of the relative enzyme activity was retained after incubation. Phytase was active over a broad range of pH (4-8), maximal activity was 0.81unit/ml when phytase incubated at pH 6 followed by 0.79 unit/ml when phytase incubated at pH 5 without significant differences between them. In addition , the enzyme was full stable at pH 5 and 6 for 1 h of incubation at 37^oC. phytase activity didn’t reach 70% at the other pH values. Hence it is inferred that the phytase was active over a broad range of  pH 4-8. Among various metal ions, only MgSO₄ has a syregenic effect with phytase activity in which activity increased as residual activity was 117.36% , while CuSO4 and ZnCl were the most inhibitory agents for P.ostreatus phytase.