Ethyl ester production with immobilized lipase in tin modified SBA‐15: Effect of the support characteristic and reaction conditions

Abstract

This study investigated the use of immobilized lipase in SBA‐15 and pore‐expanded SBA‐15 surface modified with tin, denoted as SnS23B (mean pore size of 21.6 nm) and SnS8B (with mean pore size of 9.6 nm), respectively, to produce ethyl esters. The effects of various reaction parameters, including biocatalyst type, oil (refined and degummed soybean oil), water addition, oil‐to‐ethanol molar ratio, immobilized lipase concentration, agitation speed, reaction temperature, and glycerol addition, were examined. The optimal conditions were found to be the use of SnS23B as the biocatalyst, degummed soybean oil as the substrate, 1% (w/w oil) water, 1:3 oil‐to‐ethanol molar ratio, 5% (w/w oil) immobilized lipase, 800 rpm agitation speed, and 25°C reaction temperature. The presence of glycerol negatively impacted the reaction. Under the optimal conditions, the mass percent of ethyl ester obtained was 98.2% ± 0.16. The immobilized lipase showed stability, as no lipase activity was detected upon removing the biocatalyst from the reaction. However, the biocatalyst lost 50% of its activity after 10 successive reactions, likely due to thermal deactivation and lipase inhibition caused be the adsorption of glycerol and other chemical species. Attenuated total reflectance analysis supported this hypothesis.