Enzymatic synthesis of butyl stearate in solvent-free system

Butyl stearate is an ester obtained by the esterification of stearic acid and butanol, which is used a solvent and spreading agent for creams and creamy lotions. It has been important for the cosmetics industry as it often acts as substitute for mineral and vegetable oils. It also has emollient properties, having the advantage of not leaving the greasy sensation on the skin and providing the sensation of softness. Considering the importance of this ester, this work aimed to evaluate the enzymatic production of butyl stearate. All experiments for the production of this ester were conducted in an orbital shaker, varying the agitation of 150 at 250 rpm and substrates molar ratio of 1:1 at 1:7 (acid:alcohol), while the temperature (60 °C) and enzyme concentration (1%, wt of acid) were kept constant. First, two immobilized commercial enzymes were tested (Novozym 435 and NS 88011), where the enzyme that gave the best results (conversion of 84%) was the Novozym 435. So, the optimization of butyl stearate production was performed using Novozym 435. The best result, conversion of 92%, was observed in the condition of 60 °C, substrates molar ratio of 1:2, 1 wt% of the enzyme, 200 rpm and with the addition of alcohol fractionated in three portions in the first hours of reaction. The biocatalyst reuse was also evaluated, leading to satisfactory results, 70% of conversion after five cycles of use.