Esters are highly relevant industrial compounds. They can be produced via biocatalysis in accordance with the Green Chemistry Principles using immobilized lipases, a highly specific catalyst for esterification that operates under mild reaction conditions. However, the adoption of biocatalysis for ester production is mainly hindered by the high cost of immobilized lipases relative to the selling prices of most alkyl esters. Moreover, most studies of enzymatic ester synthesis in the literature focus only on reaction conversion, dedicating less attention to process metrics and the techno-economic drawbacks of biocatalytic processes. This study presents a process metrics – oriented evaluation of enzymatic alkyl ester synthesis catalyzed by immobilized lipases, aiming to support more rational and economically relevant process development. Solvent-free syntheses of ethyl and octyl esters (acetate, caprate, and oleate) were carried out using immobilized Candida antarctica lipase B (Novozym 435). Mid- and long-chain esters showed higher conversions and superior process metrics compared to short-chain systems, mainly due to reduced inhibition and more favorable reaction media. Although excess alcohol improved conversion in some cases, it often reduced product concentration and volumetric productivity, highlighting the importance of jointly evaluating metrics such as space-time yield, catalytic productivity, and added-value index. n -Octyl acetate synthesis was selected for process design, simulation, and preliminary techno-economic assessment, revealing that despite high conversion and improved catalytic productivity via biocatalyst reuse, the process remains economically unfeasible due to the high contribution of enzyme cost to operational expenditures. The integration of process metrics with reaction engineering and techno-economic analysis provides a robust framework for bridging the gap between laboratory optimization and industrial implementation of biocatalytic processes.
Sousa et al. (Tue,) studied this question.