Enzymatic synthesis of Isopropyl stearate, a cosmetic emollient: optimisation and kinetic approach

Isopropyl stearate is used in cosmetics and personal care products as an emollient. The current work highlights the biocatalytic synthesis of isopropyl stearate in the absence of organic solvent. The reaction parameters were studied by one factor at a time method to evaluate the different factors, namely enzyme loading, molar ratio, temperature, and agitation speed. The maximum conversion of 93.89% was achieved at 3% (w/w) enzyme loading, 70°C temperature, and 1:2 acid to alcohol ratio with 200 rpm. The activation energy calculated for the esterification reaction was 10.59 kJ/mol. The Random Bi-Bi kinetic model with dead-end inhibition was suggested and validated for the enzymatic process.