Lipase-catalyzed synthesis of butyl propionate in solvent-free system: Optimization by response surface methodology

• Enzyme-based synthesis of butyl propionate in solvent-free system was studied.
• Novozym 435 was the most active biocatalyst in the reaction.
• The operating conditions for the reaction were optimized using RSM.
• Novozym 435 was reusable to reduce the production cost.

This paper presents the lipase-catalyzed synthesis of butyl propionate from butanol and propionic acid in solvent-free system. Commercially available lipases from different sources were evaluated for their catalytic activity in the reaction. Among the tested biocatalysts, Novozym 435, which is an immobilized lipase, was found to be the most active. The reaction conditions affecting the lipase-catalyzed reaction were systematically optimized using a response surface methodology. An empirical model was developed to correlate the reaction factors to the reaction yield. A maximal reaction yield of 93.76% was obtained at 42.77 °C, at a butanol/propionic acid molar ratio of 9, at an enzyme loading of 2.35%, and at a reaction time of 24.87 h. The correspondence of the predicted and experimental yields indicated that the model was reliable in predicting the reaction yield. The reusability of Novozym 435 was also studied. Under the optimal reaction conditions, the biocatalyst could be reused at least 20 times to drive the reaction to a conversion yield of 92%.