WORKING AT CONTROLLED WATER ACTIVITY IN A CONTINUOUS PROCESS - THE GAS-SOLID SYSTEM AS A SOLUTION

Fusarium solani cutinase and Candida cylindracea lipase were used to c atalyze a transesterification reaction in a continuous gas/solid biore actor. In this system, a solid phase composed of a packed enzymatic pr eparation was continuously percolated with carrier gas which fed subst rate and removed reaction products simultaneously. Different condition s of immobilization were used and compared to the results obtained wit h a nonsupported enzyme. The enzymatic activity was found to be highly dependent of a key parameter: water activity (a(w)). Biocatalyst stab ility was greatly influenced by water activity and the choice of immob ilization technique for the enzymatic material. For free and adsorbed enzymes, water requirements exhibited optima which corresponded to the complete hydration coverage of the protein. These optima presented a good correlation with the isotherm sorption curves obtained for the di fferent preparations. In this work are reported the results concerning the possibility of using a continuous system able to operate at contr olled water activity in a heterogeneous medium. Lipolytic enzyme in su ch a system appears to be a new process for the biotransformation of v olatile esters. (C) 1995 John Wiley and Sons, Inc.