Enzyme-catalysed synthesis of plant steryl laurate in non-aqueous media using salt hydrate pairs and its characterisation

The objective of this work was to produce plant steryl esters with lipase-catalysed esterification using salt hydrate pairs in n-hexane and study its cholesterol-lowering properties. The optimum reaction conditions investigated were the lipase variety (Candida rugosa lipase), fatty acid variety (laurate acid), water activity (aw = 0.764 [Na2SO4/Na2SO4·10H2O]), temperature (45 °C), and enzyme load (10%). The following kinetic parameters were determined: Vmax = 18.41 mmol/min/mg; KA,acid = 0.00407 M; KB,sterol = 0.00447 M; KiA,acid = 0.00205 M; KiB,sterol = 0.00865 M. These data showed that the bioreaction followed the Michaelis-Menten equation with a Ping-Pong Bi-Bi mechanism. FT-IR and MS analyse were adopted to confirm the chemical structure of synthesized plant steryl laurate. Compared with plant sterols, the isolated plant steryl laurate had low melting temperature and higher solubility. The cholesterol-lowering property of plant steryl laurate was also evaluated and demonstrated to decrease serum total cholesterol and low-density lipoprotein cholesterol.