Immobilisation of Acinetobacter calcoaceticus using natural carriers

There is a growing interest to immobilize desired bacteria using inexpensive materials in order to improve the wastewater treatment process. Three different types of carriers namely natural zeolite, magnesium-exchanged natural zeolite and quartz sand of different particle size were used to immobilize the phosphate-accumulating bacteria Acinetobacter calcoaceticus and to determine which one was the most effective. Bacteria were cultured for 24 h in various reactors containing different particle sizes of each of the carriers. The majority of the cultured bacterial population was immobilised onto the different carriers by means of adsorptive growth while a minority of free cells was observed in the supernatant. The number of immobilised viable cells (CFU) depended on the type of carrier and the particle size. The highest loading rate of immobilised cells (68.61±1.11 x 108 CFU/g) was observed with the smallest particle size (<0.125 mm) of magnesium-exchanged natural zeolite.