GROWTH AND PHOSPHATE-UPTAKE OF IMMOBILIZED ACINETOBACTER CELLS SUSPENDED IN ACTIVATED-SLUDGE MIXED LIQUOR

Immobilization of Acinetobacter cells can provide a method which could possibly be used to explain the mechanism of biological phosphorus re moval from AS systems since this may allow the study of pure cultures in their natural habitat. Pure cultures of Acinetobacter johnsonii and Acinetobacter calcoaceticus cells were therefore immobilized within a lginate beads (3% and 3.5% alginate) to assess their behaviour and par ticularly, their survival, leakage, growth and phosphate uptake abilit ies. Both species survived immobilization conditions, however, the eff ects on viability, leakage rate, growth and phosphate uptake were depe ndent upon the alginate concentration and the strain. Notwithstanding leakage, cell densities within alginate beads over 24 h were higher th an initial densities due to growth. The growth rate of A. calcoaceticu s immobilized cells was twice that of free cells, while A. johnsonii s howed similar growth rates between immobilized and free cells. Non gro wing immobilized cells showed higher phosphate uptake ability than gro wing cells. After 24 h, A. calcoaceticus immobilized cells removed mor e phosphate per cell than A. johnsonii cells while both species showed higher phosphate uptake ability when immobilized in 3% alginate than in 3.5% alginate.