Kinetic studies on the transesterification of sunflower oil with 1-butanol catalyzed by Rhizomucor miehei lipase in a biphasic aqueous-organic system

• Sunflower oil transesterification with 1-butanol was investigated.
• Reactions were carried in a biphasic system (water – n-hexane).
• Free Rhizomucor miehei lipase was used as the catalyst.
• Inhibition from 1-butanol was observed.
• The experimental data were successfully modelled with the Ping-Pong Bi–Bi mechanism.

The kinetics of sunflower oil transesterification with 1-butanol using a homogeneous lipase (Rhizomucor miehei) in an aqueous-organic biphasic system were studied in a stirred batch reactor set-up. An initial screening study was performed to optimize relevant process conditions (enzyme concentration, stirring speed, 1-butanol to oil ratio). A kinetic model was developed based on concentration time profiles. Important reaction parameters were the oil concentration in n-hexane, the enzyme concentration, the 1-butanol to oil molar ratio; the organic to an aqueous solvent volume ratio, the temperature, the pH setting using a phosphate buffer and the agitation rate. The experimental data were modelled using the Ping Pong Bi Bi mechanism with non-competitive inhibition by 1-butanol and a term for irreversible enzyme deactivation during reaction. Agreement between model and experiments was good (R2 = 0.99, average error 4.2%).