Statistical experimental design for evaluation of medium components for lipase production by Rhizopus arrhizus MTCC 2233

The Plackett-Burman experimental design was used to evaluate the medium components for lipase production by Rhizopus arrhizus in submerged batch fermentation. Twelve medium components with three dummy variables were studied in this experimental design. The most significant variables affecting lipase production were found to be olive oil, peptone, KH₂PO₄, CaCl₂·2H₂O and MgSO₄·7H₂O. Maximum lipase activity (3.98 U mL^-1) and maximum cell mass concentration (5.62 g L^-1) were obtained using the optimised medium. Unstructured kinetic models were analysed to simulate the experimental values of cell growth, lipase activity and glucose concentration. The logistic model for cell growth, the Luedeking-Piret model for lipase production and a modified Luedeking-Piret model for substrate utilisation were found to accurately predict the fermentation kinetics. The estimated values of the kinetic model parameters, α and β, for lipase production indicate that the lipase production by R. arrhizus is growth-associated.