Enzymatic esterification for the synthesis of butyl stearate and ethyl stearate

This work reports the enzymatic synthesis of butyl stearate and ethyl stearate, two esters with important industrial properties, ranging from cosmetic applications to emollient characteristics (butyl stearate) to food industries, imparting flavor and aroma to beverages and foods (ethyl stearate). Here, reactions were carried out using Novozym 435 as biocatalyst, considering different stirring levels and substrates molar ratios, to determine optimal conditions to produce both esters. The kinetics under optimized conditions, varying the substrates molar ratio was performed and the influence of the fractional addition of the alcohol in the reaction was also verified. It was observed for butyl and ethyl stearate that satisfactory results (92%) occurred when batch kinetics was carried out for 24 h at 60 °C, 1% (by weight of substrates) of the enzyme, agitation of 250 rpm and molar ratio of 1:2 and 1:5, respectively. Enzyme reuse up to five and three cycles led to satisfactory results for butyl stearate and ethyl stearate, respectively. This work represents, therefore, a novelty in the production of these esters by enzymatic route, leading to a high conversion of products, using a low amount of biocatalyst, proving the relevance of the production of these esters by enzymatic means, which makes the process ecologically correct and still add value to the final product.