ORGANIC-PHASE ENZYMATIC ESTERIFICATION IN A HOLLOW-FIBER MEMBRANE REACTOR WITH IN-SITU GAS-PHASE WATER ACTIVITY CONTROL

Several reactor designs have been described in the recent literature f or continuous organic phase enzymatic esterification reactions. While these designs have excellent performance characteristics, there are op erational constraints in their use. The present article describes a ne w reactor design, the gas-phase hollow fiber reactor (GPHFR), which do es not suffer from any such limitations. The reactor consists of, comm only available, hollow fiber dialyzer modules with enzyme immobilized on the lumen of the hollow fiber membranes by ultrafiltration. Substra te mixtures are passed through the fiber lumens and subjected to ester ification with a constant humidity gas phase recirculated through the shell of the reactor, acting as the medium used to control water activ ity. The simplicity of the device renders it suitable for use over a w ide range of water activities, and its modular nature facilitates easy scale-up. The use of the reactor for the fixed water activity esterif ication of an equimolar mixture of dodecanol and decanoic acid has bee n described. Under optimum conditions the reactor was found to give yi elds of ester as high as 97%. In continuous operation the immobilized enzyme was found to have a half-life of about 70 days.