Extremely low frequency magnetic field enhances glucose oxidase expression in Pichia pastoris GS115

GOX encoding gene from A. niger was expressed in P. pastoris GS115 employing methanol inducible AOX1 promoter. From resistant transformants to high zeocin concentrations, maximum GOX expressing transformant was isolated and used throughout the study. Optimal environmental conditions for achieving maximum glucose oxidase (GOX) production was determined by varying temperature (20-30 °C) and final methanol concentration from 0.25-1% (v/v). Maximum GOX production was obtained at 20 °C and 0.25% (v/v) final methanol concentration. Exposure carried out at extremely low frequencies ranging from 1 to 5 Hz and the field strength of 30-100 mT unceasingly. Biomass, GOX, protease productions and cell viability were examined in exposed and non-exposed groups every 12 h up to 96 h. Among different exposure conditions, the frequency of 2.8 Hz significantly increased GOX production and cell viability, decreased non-specific protease activity and improved biomass production regardless of changes in field intensity. Overall, supported by results, P. pastoris exposure to ELF-MF in certain circumstances could effectively further increase maximum production of GOX as achieved by optimized preliminary environmental parameters.