[Effects of mixed carbon sources on glucose oxidase production by recombinant Pichia pastoris]

Glucose oxidase (GOD) is an important industrial enzyme with many potential applications. In order to increase the production and productivity of GOD by recombinant Pichia pastoris GS115, we investigated the feeding strategies of mixed carbon sources during induction phase, based on results of the optimization of initial cell and methanol concentration on GOD production. The optimal initial cell and methanol concentration were 100 g/L and 18 g/L. During induction phase, the mixed-carbon-sources strategies showed that glycerol, sorbitol or mannitol co-feeding with methanol could enhance GOD production. With mannitol co-feeding (20:1(W/W)), the maximum GOD production and maximum GOD productivity reached 711.3 U/mL and 4.60 U/(mL x h) after an induction period of 156 h. Compared to the control, the enhancements of GOD production and productivity were 66.3% and 67.9%, respectively. Meanwhile, we found an appropriate mannitol co-feeding strategy that would not inhibit the expression of promote. The activity of alcohol oxidase was 8.8 U/g, which was enhanced by 69.2% compared to the control (5.2 U/g). We can use the same optimization process to improve the production of other proteins from recombinant Pichia pastoris by changing the fermentation parameters.