Kinetic study on partial hydrolysis of palm oil catalyzed by Rhizomucor miehei lipase

Abstract

A kinetic study on partial hydrolysis for the production of diacylglycerol (DAG) catalyzed by Rhizomucor meihei (Lipase RM IM) was investigated. The optimum conditions were estimated to be 10% (w/w) catalyst with 5% (w/w) water content at 55 °C with stirring speed of 500 rpm based on the initial reaction velocity of 7.04 mmol/L/min. At optimum conditions, the DAG yield was 31 wt% after 6 h of reaction. The rheological properties of both untreated palm oil and DAG-enriched palm oil were also investigated and both exhibited Newtonian flow behavior with insignificant differences with respect to their viscosity and flow activation energy. Activation energy for the partial hydrolysis of palm oil was calculated to be 31.35 kJ/mol using Arrhenius equation. Morphological evaluation of enzyme particles revealed that high speed rate might devastate the enzyme particles as those particles were susceptible to mechanical force. A ping-pong bi-bi with substrate competitive inhibition by water kinetic model had been proposed to simulate the reaction kinetic of partial hydrolysis. The kinetic constants Vmax, Km (palm oil), Km (water) and Ki were evaluated to be 17.39 mmol/L/min, 0.55 mmol/L, 1.04 mmol/L and 2.68 mmol/L, respectively using non linear regression analysis with the computer program Microsoft Excel Solver. The model proposed was found to accurately represent the experimental data with determination coefficient R2 of 0.99.