Optimization of reaction parameters for the synthesis of natural aroma esters by factorial design†

In this study, the synthesis of aroma esters by the direct esterfication of carboxylic acids with aromatic alcohols mediated by lipase B from Candida antarctica encapsulated in a sol–gel matrix in a solvent-free system is presented. Vacuum was used in order to remove the resultant water. The reaction parameters were optimized by factorial design experiments considering four factors (acid excess, temperature, vacuum and time) on two levels. As a result, the conversions were significantly increased (for example, from an isolation yield of 49.4% to 94.3% for cinnamyl butyrate). A semi-preparative experiment was further set up for cinnamyl butyrate preparation. The green chemistry metrics, such as the E-factor of 4.76 and mass intensity of 6.04, demonstrated that the newly developed enzymatic process is suitable for industrial application based on green chemistry principles.