Kinetic resolution of (R,S)-α-tetralol by immobilized Candida antarcticaLipase B: comparison of packed-bed over stirred-tank batch bioreactor

Abstract

Here, we have demonstrated the flow chemistry approach for kinetic resolution of (R,S)-α-tetralol using the packed-bed reactor of immobilized Candida antarctica lipase B (Novozym 435). We have investigated the performance of different enzymes including Lipozyme RM IM, Lipozyme TL IM, and Novozym 435 and compared their activity and enantioselectivity in nonaqueous media. The kinetics of transesterification of (R,S)-α-tetralol using vinyl acetate as the acylating agent was studied in a packed bed of immobilized enzyme. A continuous-flow packed bioreactor shows better behavior in terms of enantioselectivity and conversion vis-à-vis a stirred-tank reactor. A conversion of ∼50% of the (R,S) mixture with ∼100% selectivity (E) for (R)-α tetralol (eep ≥ 99.99%) was obtained at 65 °C with a 3 min residence time using Novozym 435 as the catalyst in the continuous-flow packed-bed reactor, whereas a 43.6% conversion of racemic mixture (eep ≥99.99%) was obtained in a stirred-tank batch reactor in 8 h under identical conditions. There was no back-mixing in the fixed-bed bioreactor having laminar−plug flow. The enzyme remains stable up to the seventh reuse, which shows viability of a continuous operation over a longer period. Inhibition by vinyl acetate with the ping pong bi-bi mechanism was proposed using Lineweaver–Burk plots.