Expression,Purification and Bioactivity Analysis of Porcine Epidermal Growth Factor in Recombinant Pichia pastoris by High-Density Fermentation

The recombinant Pichia pastoris strain infected with pPIC9-pEGF/GS115 for expression of strain porcine epidermal growth factor was high cell density cultured in a 5.5 L fermentor.Following pre-fermentation and reaching D600 nm density to 150,the yeast cells were induced by addition of methanol,which elevated cell density D600 nm to 315.As the result,the medium concentration of secreted pEGF reached 300 mg/L.The pEGF fermentation product was purified to 90% by ultrafiltration,His-tag affinity column chromatography and dialysis.In vitro biological activity test results showed that the expressed pEGF fusion protein could enhance significantly the proliferation of BALB/c 3T3 cells.The above results demonstrated successful preparation of biologically active pEGF by the P.pastoris eukaryotic expression system.