Abstract: In our previous work, we have isolated a protease-producing Pichia kudriavzevii yeast strain. This study was undertaken to use response surface methodology to optimize fermentation conditions for protease production by the strain. Protease activity in fermentation broth was investigated with respect to C/N ratio, MgSO4 and CaCl2 concentrations, and inoculum size. A quadratic polynomial model describing the effects of the fermentation conditions on protease production was established. The highest protease production of 2504.8 U/mL was achieved under the following conditions: C/N ratio of 2, 0.5 g/L MgSO4, 0.2 g/L CaCl2, and inoculum size of 6%, which was four times higher than before optimization. In addition, the established regression model was found to have good effectiveness in predicting protease production.

Key words: protease, corn steeping, optimization, response surface