Purification and Characterization of Phytase Enzyme Extracted from Aspergillus niger SF58 and its Application in Cereal Dephytinization

Abstract

Phytases are the group of enzymes that catalyze phytate hydrolysis and release a utilizable form of inorganic phosphorus. So, they are used to improve the nutritive value of animal feed. The current study aims to purify, characterize the phytase enzyme, and to study its application in cereal dephytinization. Molecular identification of the fungal isolate was achieved using the 18S rRNA and phytase activity was determined using phytic acid as substrate. Phytase from Aspergillus niger SF58 was purified using dialysis and Sephadex G 100 column chromatography to get enzyme recovery and purification fold of 72.74% and 2.303, respectively. The purity of purified phytase was confirmed through SDS-PAGE technique which showed a one protein band corresponding to phytase activity at 22 kDa. The optimum reaction time for phytase activity was revealed to be 15 min, whereas the optimal temperature and pH values were found to be 60 o C and pH 5.5. The purified enzyme was able to retain 46.93% of its initial activity after 4 months of storage at 4 o C. Metal ions (Co 2+ , Cu 2+ , Mn 2+ , Fe 2+ , Zn +2) acted as activators for the purified phytase, whereas Mg 2+ , Ni 2+ and Al 3+ served as inhibitors. The purified phytase showed the highest substrate specificity toward wheat bran, followed by the wheat flour, soybean , and corn-flower, respectively. The use of Aspergillus niger SF58 phytase in dephytinization of wheat bran and soybean indicated the possibility of applying the enzyme to increase the nutritional values of feed and food additives.