In this study attempts were made to investigate the effect of extremely low frequency magnetic field (ELF-MF) on expression of glucose oxidase gene from Aspergillus niger Z-25 in Pichia pastoris GS115 at optimal environmental conditions. 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 5Hz and the field strength of 30-100mT unceasingly. Biomass, GOX, protease productions and cell viability were examined in exposed and non-exposed groups every 12h up to 96h. Among different exposure conditions, the frequency of 2.8Hz 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.
Keywords: Cell viability; Extremely low frequency magnetic field; Glucose oxidase; Non-specific protease activity; Pichia pastoris.
Copyright © 2017 Elsevier Inc. All rights reserved.