EFFECT OF INITIAL BIOMASS CONCENTRATION ON THE GROWTH OF IMMOBILIZED NITROSOMONAS-EUROPAEA

Nitrosomonas europaea was immobilized in carrageenan-gel beads with a low and a high biomass concentration (100-fold difference). Under grow th conditions in a continuous air-lift loop reactor, a low initial con centration yielded a few large micro-colonies per bead, whereas a high initial biomass concentration resulted in many small micro-colonies p er bead. The macroscopic consumption rate of the latter was three time s higher under the circumstances applied. This is also predicted by ou r colony-expansion model when diffusion limitation over the micro-colo nies is incorporated. This model also predicts that diffusion limitati on over the ultimate colonies is negligible when the initial biomass c oncentration exceeds 0.5 kg.m(-3) of carrageenan gel.