Optimization of the extraction condition for wheat bran esterase in aqueous two-phase systems by response surface analysis

The extraction of wheat bran esterase by aqueous two- phase system composed of PEG / ( NH4) 2SO4was studied.The effects of molecular weight and concentration of polyethylene glycol ( PEG) , the concentration of ( NH4) 2SO4concentration, pH value and NaCl addition etc. on the distribution coefficient, activity yield and purification factor were examined. Response surface methodology was employed to optimize this system. The results showed that the optimum conditions were PEG1000 21% ( m /m) , ( NH) 2SO418% ( m /m) and pH at 4.4.Under these conditions, the purification factor could reach to 2.9208, the average degree of purification factor of three times experiment reach to 2.9190, compared with predictive value the relative error was 0.06%.