Dual-substrate inhibition kinetic studies for recombinant human interferon gamma producing Pichia pastoris

Pichia pastoris is considered as one of the prominent host extensively used as a platform for heterologous protein production. In the present study, the growth inhibition kinetics of recombinant P. pastoris expressing human interferon gamma was studied under different initial substrate concentrations of gluconate (10-100 g L^-1) and methanol (2-50 g L^-1) in modified FM22 medium. The highest specific growth rate of 0.0206 and 0.019 hr^-1 was observed at 60 g L^-1 of gluconate and 10 g L^-1 of methanol, respectively. Various three- and four-parametric Monod-variant models were chosen to analyze the inhibition kinetics. The model parameters as well as goodness of fit were estimated using nonlinear regression analysis. The three-parameter Haldane model was found to be best fit for both gluconate (R² = 0.95) and methanol substrate (R² = 0.96). The parameter sensitivity analysis revealed that µ_max, K_i, and K_s are the most sensitive parameters for both methanol and gluconate. Different substrate inhibition models were fitted to the growth kinetic data and the additive form of double Webb model was found to be the best to explain the growth kinetics of recombinant P. pastoris.