Purification, characterization, and cloning of a novel phytase with low pH optimum and strong proteolysis resistance from Aspergillus ficuum NTG-23.

A novel phytase was isolated from Aspergillus ficuum NTG-23 with a procedure involving ion-exchange chromatography on DEAE-cellulose, CM-cellulose and FPLC-gel filtration on Superdex 75. The protein exhibited a molecular mass of 65.5kDa in gel filtration and SDS-PAGE. It possessed an optimal pH of 1.3 and an optimal temperature of 67 degrees C, and manifested a K(m) of 0.295mM and a V(max) of 55.9nmol (phosphate)/min. Phytase activity was not significantly affected by metal ions such as Ca(2+), Mg(2+), Mn(2+), Zn(2+), but was slightly stimulated in the presence of EDTA. The phytase was stable at 60 degrees C with no obvious loss of activity upon its incubation at 70 degrees C for 20min. The enzyme exhibited a broad substrate selectivity and showed strong resistance toward pepsin and trypsin. The unique properties suggest that the phytase has the potential to be useful as an animal feed supplement. Copyright 2010 Elsevier Ltd. All rights reserved.