Production and some properties of extracellular phytase from Thermomyces lanuginosus IMI 096218 on rice flour as substrate

Thermophilic fungi Thermomyces lanuginosus IMI 096218 strain produces phytase enzyme on rice flour in submerged fermentation. The maximal activity was achieved on the 4th day of fermentation using 5 (w/v)% rice flour and at 220-rpm agitation speed. Additionally, the enzyme production was enhanced by supplementation of 0.1% Tween-80 detergent into fermentation medium. The phytase was purified about 9.1 fold with yield of 5.1%. The optimal pH and temperature of the purified phytase enzyme were pH 5.5 and 70 degrees C, respectively. The half-life times of enzyme at temperature 54-58 degrees C and pH range 5.0-7.5 were longer than 100 min. Kinetic parameters of phytase on sodium-phytate substrate were determined by linear Lineweaver-Burk plot: K-M=0.285 mM, v(max)=0.126 mM/min, and Hanes-Woolf plot: K-M=0.312 mM, v(max)=0.132 mM/min, respectively. The presence of 5 mM Zn2+, Ag+, Co2+ and Cu2+ ions strongly inhibited the enzyme reaction. The residual activities were 55%, 49%, 38% and 34% respectively. This phytase can be considered as a potential candidate in animal feeding as well as in the production of some intermediates for clinical applications.