Abstract

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.