To investigate the optimal medium for the production of a metagenome-derived β-galactosidase (ZQ114) by Pichia pastorisi, Plackett and Burman design was applied to screen the significance of eight medium compositions, and three factors (methanol, sorbitol and MgSO4.7H2O) were found to have significant effect on the production of ZQ114. Then, the steepest ascent method was further used to determine their optimal levels, and Box-Behnken design and response surface methodology were eventually adopted to derive a statistical model for optimizing the medium. The experimental results indicate that the optimum of three main factors was 10.43 g/L (methanol), 33.98 g/L (sorbitol), and 0.52 g/L (MgSO4.7H2O), respectively. The highest yield of ZQ114 using the optimal medium reached up to 14.94 U/mL with lactose as substrate, which was 2.57 times higher than that unoptimized. Also, the experimental data of 14.94 U/mL is basiclly accordant with the predicted value (14.68 U/mL).
Key words: β-Galactosidase, enzyme production, medium optimization, response surface methodology.
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