Synthesis of butyl butyrate in batch and continuous enzymatic reactors using Thermomyces lanuginosus lipase immobilized in Immobead 150

Abstract

Thermomyces lanuginosus lipase (TLL) was covalently immobilized on Immobead 150 (ImmTLL) via epoxy groups of the support and the lysine of the enzyme to be used in the synthesis of butyl butyrate. The optimization of the esterification reaction parameters was carried out by central composite design and response surface methodology, having product yield as target, with all tested variables showing to be statistically significant on the conversion. The optimal conditions for butyl butyrate synthesis were: temperature of 40°C, substrate molar ratio of 3:1 butanol:butiric acid, 40% of enzyme amount in relation to substrate weight, and 2.5% of water (volume fraction of reaction), using hexane as solvent. Under these conditions, over 84% of conversion was obtained after 4h of reaction in a batch reactor, with a productivity of 0.27mmolg−1h−1 per gram of derivative. The butyl butyrate synthesis was also evaluated in a continuous reactor, using two configurations: packed-bed reactor (PBR) and fluidized-bed reactor (FBR). The highest productivity per gram of derivative in the continuous process was 1.01mmolg−1h−1, reached using the PBR containing 1.5g of ImmTLL and glass beads. The biocatalyst presented operational stability at 40°C, maintaining 83% of its initial conversion capacity after 8 cycles of reuse in batch reactor and 63% after 30 days of continuous operation in the PBR, using a flow rate of 0.02mLmin−1. These results suggest that this immobilized system can be successfully used to produce butyl butyrate for food, cosmetics, and for pharmaceutical applications.