Based on statistical designs, minimal salts medium, commonly used for yeast cultivation, was optimized to maximize GAP promoter-mediated phytase production by recombinant Pichia pastoris grown on glycerol. A Plackett-Burman design was followed to screen medium components to determine those that significantly affected phytase production. Of the 8 components studied, the concentrations of K2SO4, CaSO4•2H2O and MgSO4•7H2O were identified as having a significant effect. These three components were subsequently optimized by response surface methodology using a central composite design. The optimal concentrations of the three components, leading to a maximal extracellular phytase activity of 161.64 U/ml, were K2SO4 13.25g/l, CaSO4•2H2O 1.03g/l and MgSO4•7H2O 17.94g/l. The activity measured in cultures using optimized growth medium is significantly higher than the 73.31 U/ml measured in cultures using standard minimal salts media. The theoretical phytase yields predicted by the developed model were very close to experimentally obtained values.
Optimization of expression conditions for a novel NZ2114-derived antimicrobial peptide-MP1102 under the control of the GAP promoter in Pichia pastoris X-33
