Kinetic and docking study of synthesis of glyceryl monostearate by immobilized lipase in non-aqueous media

Abstract

Glyceryl monostearate is extensively used as an emulsifier in many industries. Mono acylation of glycerol was carried out by utilizing immobilized Candida antarctica lipase B (Cal B) as a biocatalyst and vinyl stearate as an acyl donor. Different reaction parameters, such as selection of lipases from various sources (like Candida antarctica, Candida rugosa, and Mucor meihei) and their quantity, shaking speed, temperature, substrate concentration, and reusability were studied in detail to achieve excellent conversion. Overall, 98% conversion of glycerol was obtained at a mole ratio of 1:1 of glycerol to vinyl stearate, using 12 mg of immobilized Cal B at 45 °C for 3 h. The mechanism of the given reaction was anticipated based on the results of the Lineweaver-Burk plots. It was found that the reaction followed the Ping-Pong Bi Bi mechanism with inhibition of glycerol. As it was a kinetically controlled synthesis, different kinetic constants were estimated by non-linear regression analysis. The activation energy for Cal B was found to be 10.3 kcal/mol. Further, biocatalyst can be reused up to four catalytic cycles with an average four percent loss of activity. A molecular docking study was done to find out the confirmation of substrates and their binding positions in an enzyme. It was noticed that the reaction proceeds through acyl-enzyme complex formation followed by the transfer of that acyl group to another substrate.