Optimization of reaction conditions in production of cycloisomaltooligosaccharides using enzyme immobilized in multilayers onto pore surface of porous hollow-fiber membranes

Anion-exchange porous hollow-fiber membranes were prepared by graft polymerization of an epoxy group-containing monomer and subsequent ring-opening of the epoxide with diethylamine. Cycloisomaltooligosaccharide glucanotransferase (CITase) was bound by the anion-exchange polymer chains onto the membrane, and cross-linked with transglutaminase. CITase was immobilized at a density of 38 and 110 mg-CITase/g, equivalent to the degree of immobilized enzyme multilayering, which is defined by the ratio of the immobilized amount to the theoretical monolayer binding capacity, of 3.5 and 9.8, respectively. Seven- to nine-glucose-membered cycloisomaltooligosaccharides (CIs) were produced during the permeation of a dextran solution at various buffer concentrations, pHs, and temperatures through the pores rimmed by the CITase-immobilized polymer chains. Optimum pH and temperature were 6–7 and 323 K, respectively. The yield of CIs decreased with an increase in space velocity (SV), which is defined by dividing the permeation rate of the dextran solution by the membrane volume. A maximum yield of 45% was observed in the circulation mode under optimized reaction conditions.