REACTOR HETEROGENEITY WITH SACCHAROPOLYSPORA-ERYTHRAEA AIRLIFT FERMENTATIONS

Bioreactor heterogeneity has been studied in a multiconfigurable pilot -scale airlift reactor (0.25 m(3)) which created different degrees of heterogeneity. The impact of the two sparger configurations, i.e. in t he draft tube or the annulus, in conjunction with a marine propeller f itted at the base of the downcomer, on the physiology of Saccharopolys pora erythraea was studied. Cellular growth, morphology, and productiv ity were compared between airlift and stirred tank reactors. Dissolved oxygen tension heterogeneity caused by differences in dissolved oxyge n tension around the vessel did not affect growth, but the reduction o f heterogeneity improved the specific erythromycin production rate and final specific production. Erythromycin production was shown to be pr oportional to the energy dissipation rate. The enhancement of bubble c oalescence with increasing apparent viscosity led to the reduction of the sectional gas holdups and the improvement of liquid mixing. The ex tent of the changes with increasing apparent viscosity was dependent o n the broth morphology, reactor configurations, and operating conditio ns. (C) 1998 John Wiley & Sons, Inc.