Immobilisation of Acinetobacter johnsonii cells within alginate beads

Abstract

The growth and distribution of A. johnsonii cells, immobilised within alginate beads suspended in an aerated activated sludge mixed liquor medium, were assessed by viable cell counts on nutrient agar and scanning electron microscope (SEM). Both techniques indicated that A. johnsonii cells did survive and grow within alginate beads. A. johnsonii immobilised cells were metabolically active as they removed phosphate from the activated sludge mixed liquor medium. While cells were expected to occur preferably in the outer layer after a few hours of incubation, beads entrapping bacterial cells showed a random distribution of cell colonies 24h and 2 weeks after incubation. This constant random distribution might be attributed to constant aeration that would have fascilitated mass transfer added to extracellular substances which maintained daughter cells in colonies close to one another, thus preventing them from moving to the outer layer.