Purification and Characterization of Phytase Produced by Aspergillus niger Isolated from Poultry Farm Soil Using Submerged Fermentation

Abstract

Phytase is used in feed processing as an exogenous supplement in monogastric animal feed. This study was aimed at determining phytase production capacity of Aspergillus niger isolated from poultry farm soil. A. niger was isolated from poultry farm soil using phytase screening medium (PSM) containing sodium phytate as substrate. Quantitative estimation of phytase production was carried out by submerged fermentation using 3 x 10 5 spores/100 mL PSM for 5 days at 30 o C and 150 rpm. The obtained crude phytase was purified using a combined purification process of ammonium sulphate precipitation and gel filtration chromatography using a 50 x 1.5 cm Sephadex G-75 column. The activity of the partially purified enzyme was assessed by subjecting it to varying pH, temperature, and nutrient conditions. The optimum temperature and pH were 50 o C and 6 respectively. The enzyme remained active for over 30 min at 70 o C and completely lost activity after 10 min at 80 o C. No activity was observed at 100 o C. The phytase produced with glucose as carbon source had higher activity (0.087 U/mL) than that produced with sucrose (0.018 U/mL). The A. niger isolate used in this study was unable to utilize ammonium sulphate as a source of nitrogen (no activity). This study establishes the potential of indigenous fungi for industrial phytase production.