IMMOBILIZATION OF CYCLODEXTRIN GLUCANOTRANSFERASE ON CAPILLARY MEMBRANE

A bioreactor system with the enzyme immobilized on a capillary membrane is a promising tool for the mass production of valuable substances, because of the good productive efficiency. To investigate the kinetics of immobilized cyclodextrin glucanotransferase ([EC 2.4.1.19]; CGTase) on a capillary membrane in a bioreactor system, the amount of immobilized CGTase and the operating conditions, such as pressure and the reaction temperature, were examined under a constant substrate concentration (1.0%) and a constant flow rate (0.12 m/s). When the CGTase was immobilized at a concentration of 0.04 to 0.62 mg per membrane area (cm(2)), the decrease in the immobilized amount of CGTase resulted in an increase in the cyclodextrin production rate (g of CD/h.m(2); CPR) and the CPR correlated well with the flux of the CGTase-immobilized membrane. Although a higher reaction temperature caused an increase in the CPR within a short operating time of the bioreactor, repeated operation at 60 degrees C led to a reduction in the CPR due to the denaturation of the immobilized CGTase. The percentage of cyclodextrin (CD) to total sugar obtained in the permeate was slightly more than 60% under most operating conditions, but immobilization of the excess amount of CGTase (0.42-0.62 mg/cm(2)) reduced the CD yield as well as the ratio of alpha-CD to beta-CD, suggesting that it led to a CGTase side-reaction such as intermolecular transglycosylation. These data suggest that the conditions under which the bioreactor with 0.04-0.40 mg/cm(2) was operated; a reaction temperature of 50 degrees C, a residence time of 1-2 min and adjustable pressure, could be employed to obtain a high CPR using a large scale CGTase-immobilized membrane bioreactor.