Expression of recombinant Pichia pastoris X33 phytase for dephosphorylation of rice bran fermented liquid

Abstract

The Aspergillus ficuum phytase gene phyA was overexpressed in Pichia 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.