Expression of recombinantPichia pastoris X33 phytase for dephosphorylation of rice bran fermented liquid

Abstract

TheAspergillus ficuum phytase genephyA was overexpressed inPichia pastoris X33 after replacing Buffered glycerol-complex medium (BMGY medium) using 1% (v/v) glycerol with fresh Buffered methanol-complex medium (BMMY medium) using 1% (v/v) methanol (on daily basis) as carbon sources. The phytase activity increased evidently with the induction time, and reached 200 U mL⁻¹ after 9 days of induction. We examined the possibility of employing thus obtained phytase to recover phosphorus from the fermented liquid of rice bran. When the 0.1 M sodium acetate buffer was replaced with de-ionised water (pH 5.5±0.1) as an enzyme reaction solution, there was an increase in the phosphorus recovery with respect to time and reached 1.31% after 24 h incubation contributing to 81% release of inorganic P from the rice bran phytate. Studies on hydrolysis of rice bran phytate by the addition of different concentrations of phytase ranging from 0–200 U mL⁻¹ produced through the recombinant yeast shows no significant effect in the rate of phytate hydrolysis at enzyme activities of 200, 100, 50 U mL⁻¹. However, rate of hydrolysis varied significantly at 20, 5, 0 U mL⁻¹ enzyme concentrations.