|Title:||Expression of recombinant Pichia pastoris X33 phytase for dephosphorylation of rice bran fermented liquid||Authors:||Ming-Hui Chang
|Keywords:||phytase;Pichia pastoris X33;phosphorus;rice bran;SDS-PAGE||Issue Date:||2008||Publisher:||Springer||Journal Volume:||58||Journal Issue:||2||Start page/Pages:||233-238||Source:||Annals of Microbiology||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.
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