Optimization of abiotic factors for improved growth and extracellular production of recombinant fungal phytase in sesame hairy root cultures

Abstract

The effects of various abiotic factors, including polyethylene glycol (PEG), silver nitrate (AgNO3) and potassium phosphate (KH2PO4) on biomass growth, extracellular production of recombinant fungal phytase and its transcription activity by realtime RT-PCR were examined with transformed sesame hairy roots. The PEG treatments decreased both biomass growth (80.5≈82.3%) and phytase production (82.1≈96.4%) at all concentrations tested, except 1.0 g/L PEG, which increased biomass growth to 112.4% of that of the control. The AgNO3 treatments also resulted in reduced biomass growth (77≈92%) and phytase production (84.4≈96.3%) at all concentrations applied except 1.5 mg/L AgNO3, at which biomass was increased to 109.6% of that of untreated roots. The potassium phosphate treatments increased biomass growth, production of recombinant fungal phytase and its transcription until a concentration of 340 mg/L was attained, and at 510 mg/L a rapid decrease was observed in all of the aforementioned parameters. Combined treatments of PEG (1 g/L) and AgNO3 (1.5 mg/L) exhibited both positive and negative influences on biomass growth and production and transcription of the recombinant fungal phytase when medium containing 170 and 340 mg/L of potassium phosphate were used, respectively. The addition of PEG alone to culture medium containing potassium phosphate at both of the aforementioned concentrations decreased biomass while increasing production and transcription of recombinant fungal phytase. Conversely, the addition of AgNO3 alone to culture medium increased biomass but decreased production and transcription of fungal phytase. Throughout these experiments, the most effective treatment for enhanced biomass growth, and enhanced production and transcription of recombinant fungal phytase was attained when the 1 g/L PEG and 1.5 mg/L AgNO3 were combined in medium containing 340 mg/L potassium phosphate.