Study of glycerol-methanol and sorbitol-methanol mixed feed strategies for recombinant hPDGF-BB production in Pichia pastoris

Abstract

The recombinant human platelet-derived growth factor type BB (rhPDGF-BB) protein has been approved by FDA for diabetic foot ulcer treatment due to its function of stimulating cell proliferation and wound healing. In this study, the production of rhPDGF-BB from Pichia pastoris is studied in a 7.5 L fermentation using methanol as carbon source and inducer in induction phase. The specific growth rate of the recombinant strain reduced 1.833-fold and rhPDGF-BB productivity reduced 2.13-fold compared to at 0.5 L. To improve growth and protein expression of the strain in induction phase, the mixed feed strategy, in which glycerol or sorbitol was co-fed with methanol at three different molar ratios (1:1, 1:2 and 1:3) was conducted. Using the mixture of glycerol and methanol at the molar ratio 1:2 and the mixture of sorbitol and methanol at the molar ratio 1:3 increased the productivity of rhPDGF-BB protein 1.32-fold (280,48 mg/L) and 1.24-fold (264,15 mg/L), respectively, higher than using only methanol in the induction phase of the fermentation process.