IMMOBILIZATION OF CYCLODEXTRIN GLUCANOTRANSFERASE ON CAPILLARY MEMBRANE

A bioreactor system with the enzyme immobilized on a capillary membran e 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 immobi lized CGTase and the operating conditions, such as pressure and the re action temperature, were examined under a constant substrate concentra tion (1.0%) and a constant flow rate (0.12 m/s). When the CGTase was i mmobilized 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 membr ane. Although a higher reaction temperature caused an increase in the CPR within a short operating time of the bioreactor, repeated operatio n at 60 degrees C led to a reduction in the CPR due to the denaturatio n of the immobilized CGTase. The percentage of cyclodextrin (CD) to to tal sugar obtained in the permeate was slightly more than 60% under mo st operating conditions, but immobilization of the excess amount of CG Tase (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 th e conditions under which the bioreactor with 0.04-0.40 mg/cm(2) was op erated; 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.