ON THE ROLE OF REACTIVE DIFFUSION AND PELLET SHAPE IN THE CONVERSION OF RIFAMYCIN-B TO RIFAMYCIN-S BY IMMOBILIZED RIFAMYCIN OXIDASE

The steady state performance of a well-mixed continuous flow bioreacto r has been analysed for the conversion of rifamycin B to rifamycin S b y rifamycin oxidase immobilised inside porous pellets. Substrate inhib ition kinetics, established in a previous study, have been used and a one-point collocation employed for the concentration profiles in the p ellets. The effectiveness factor, eta, and the fractional conversion, X, of rifamycin B for rectangular, cylindrical and spherical pellets p ass through peaks as the Thiele modulus is varied. The maxima for both eta and X are highest and occur at the smallest Thiele modulus for a rectangular slab whereas a sphere is at the other extreme. While this favours a rectangular pellet, the superior mechanical strength of a sp here may be exploited by coating enzyme-bearing material on an inert c ore. An interesting comparison with the same reaction using free enzym e is that input multiplicity is still present in the fluid phase even when reaction occurs in the pellets.