Statistical evaluation of medium components by Plackett-Burman experimental design and kinetic modeling of lipase production by Pseudomonas fluorescens

Abstract

The evaluation of medium components for lipase production by Pseudomonas fluorescens in submerged batch fermentation was studied using Plackett-Burman experimental design. Twelve medium components with three dummy variables were studied in this experimental design. The most significant variables affecting lipase production were found to be glucose, olive oil, yeast extract, dipotassium hydrogen phosphate and ferrous sulphate heptahydrate. Maximum lipase activity of 3.32 U mL⁻¹ and maximum cell mass concentration of 2.15 g L⁻¹ was obtained in the 32 h of fermentation using the optimized medium under optimized conditions of 30ºC, with an initial pH of 7.0 at 120 rpm. Various unstructured kinetic models were analyzed to simulate the experimental values of cell growth, lipase activity and glucose concentration. Logistic model for cell growth, Luedeking-Piret model for lipase production and modified Luedeking-Piret model for substrate utilization were found to predict the fermentation profile more accurately with high determination coefficient (R²) values of 0.9893, 0.9314 and 0.9765, respectively. The estimated values of the kinetic model parameters, α and β for lipase production clearly indicate that the lipase production by P. fluorescens is growth-associated.