CONTINUOUS IN-SITU WATER ACTIVITY CONTROL FOR ORGANIC-PHASE BIOCATALYSIS IN A PACKED-BED HOLLOW-FIBER REACTOR

Packed bed hollow fiber membrane reactors were used to carry out organ ic phase biocatalysis at constant water activity. The performance of t he device was tested by carrying out the esterification of dodecanol a nd decanoic acid in hexane. Lipase from Candida rugosa, immobilized on microporous polypropylene and packed in the shell space of the reacto r, was used to catalyze the reaction. In situ water activity control w as accomplished by pumping appropriate saturated salt solutions throug h the microporous hollow fiber polypropylene membranes. Water generate d by reaction in the organic phase, pumped continuously through the sh ell of the reactor, was transferred into the bulk of the aqueous phase under the water activity gradient. The reactor performance was found to be strongly dependent on the controlling water activity. By careful ly selecting this control activity it was found possible to obtain com plete esterification. The water activity of the organic phase could be maintained very close to that of the saturated salt solution used. Th e reactor could be operated in the continuous mode for 100 h without a ny degradation in its performance. (C) 1996 John Wiley & Sons, Inc.