Enhancement of cell viability and alkaline polygalacturonate lyase production by sorbitol co-feeding with methanol in Pichia pastoris fermentation

Alkaline polygalacturonate lyase (PGL) production by Pichia pastoris GS115 was used as a model to study the mechanism and strategy for enhancing heterologous protein production. In order to enhance cell viability and volumetric recombinant protein productivity, sorbitol, which had been confirmed to be a non-repressive carbon source, was added together with methanol during the induction phase. The resultant PGL activity was up to 1593 U mL−1, which was enhanced 1.85-fold compared to the control (863 U mL−1) cultured with sorbitol added at a constant rate of 3.6 g h−1 L−1 after an induction period of 100 h. Further results revealed that an appropriate sorbitol co-feeding strategy not only decreased the cell mortality to 8.8% (the control is about 23.1%) in the end of fermentation, but also reduced the proteolytic degradation of PGL.