THERMAL STABILIZATION OF IMMOBILIZED LIPASE B FROM CANDIDA-ANTARCTICAON DIFFERENT SUPPORTS - EFFECT OF WATER ACTIVITY ON ENZYMATIC-ACTIVITY IN ORGANIC MEDIA

Covalent immobilization of C. antarctica lipase B (CALB) on sepharose, alumina, and silica was undertaken. The thermal stability of these co valently immobilized catalysts were studied and compared to adsorbed d erivatives from Novo Nordisk at 50 degrees C under wet conditions. Nat ive enzyme and Novozym 435 follow a deactivation model E --> E-1 where as covalently immobilized derivatives and SP435A follow the model E -- > E-1 --> E-2. This different behavior is related to the nature of the support and the immobilization methodology. Water absorption isotherm s of dry solid biocatalysts in air or isooctane were used to predict t he optimum preequilibrium a(w) value to obtain the highest rate in the esterification of (R,S)-ibuprofen. (C) 1998 Elsevier Science Inc.