Optimization of immobilization conditions of Thermomyces lanuginosus lipase on olive pomace powder using response surface methodology

In this work, microbial lipase from Thermomyces lanuginosus was immobilized onto olive pomace. Response surface methodology was used to optimize the conditions for the maximum activity and to understand the significance and interaction of the factors affecting the specific activity. 5-level-3-factor central composite design was employed to evaluate the effects of immobilization parameters such as enzyme concentration (3–15%, v/v), pH (5.0–9.0) and buffer concentration (20–100 mM) on the specific activity of immobilized lipase. Quadratic polynomial equation was obtained for predicting specific activity of immobilized lipase. The predicted specific activity was 6.00 μmol p-NP/mg enzyme min under the optimal conditions. Verification experiment (6.21 μmol p-NP/mg enzyme min) confirmed the validity of the predicted model. Immobilized lipase was used to determine operational stability and it indicated that immobilized lipase was stable retaining more than 80% residual activity after being used repeatedly for 10 consecutive batches of pomace oil transesterification.