Immobilization of Nitrosomonas europaea cells with polyelectrolyte complex

Cell immobilization with polyelectrolyte complex prepared from strongly polyacidic and polybasic ions was investigated for cells from Nitrosomonas europaea (ATCC 25978). Trimethylammonium glycol chitosan (TGCI) and potassium poly(vinyl-alcohol) sulfate (KPVS) were used. The immobilization was carried out by directly mixing both polymer solutions with the culture broth: An excess of TGCI was first added to the culture broth to aggregate the cells, and then KPVS was added to form the complex with the excess TGCI and to entrap the aggregates with the resulting complex. From physiocochemical studies on the cell aggregation, the mechanism can be interpreted in terms of the adsorption of polyion caused by the salt linkages of the ionizable groups on the cell surface. The result of an electron microscopic observation showed that the cells are situated in the pores and on the surface of the complex support. When the immobilized cells were incubated in a medium buffered by phosphate and containing ammonium sulfate, a considerable amount of nitrite was formed; this was shown to be caused by the entrapped cells and also those cells released from the support and grown in the medium. The ammonia-oxidizing activity was retained even after a total of 200 h of incubation in a batch reactor. No deformation of the complex support was observed.