Screening of engineered Pichia pastoris mutant with enhanced production of a functional rFIP-glu protein and investigating its potential bioactivities

An engineered Pichia pastoris GS115 with a FIP-glu gene was mutated using ultraviolet (UV) radiation, and a high-throughput screening method was established for screening of high-yield strains. Meanwhile, a preliminary study was conducted to determine the bioactivity of the rFIP-glu. Based on OD600 value and the mortality of engineered P. pastoris GS115, the best UV irradiation time was determined. Bradford method and SDS-PAGE method were employed to analyze the concentration and yield of rFIP-glu. Melanoma B16 cells were employed to evaluate the biological activities of rFIP-glu in vitro. Results showed that the protein yield of the best mutant #4-336 screened from 3680 mutant strains increased from 242 to 469 mu g ml(-1). In vitro assays of biological activity indicated that rFIP-glu had significant toxicity and possessed the ability to affect melanin content and enhance tyrosinase activity in B16 cells. In conclusion, an effective high-throughput screening approach was established for screening mutant strains. The screened mutant possesses a good ability to enhance the production of rFIP-glu, and recombinant proteins display a better biological activity on melanoma B16 cells. The engineered P. pastoris mutant seems promising as a potential source for industrial production of rFIP-glu and should be a candidate industrial strain for further study.