Selective immobilization of Acinetobacter junii on the natural zeolitized tuff in municipal wastewater.

The immobilization of desired bacteria onto material was usually performed in synthetic media. The aim of this study was to test the immobilization of phosphate (P)-accumulating bacteria Acinetobacter junii onto natural zeolitized tuff (NZ) in the raw or sterilized municipal wastewater containing the common bacteria Escherichia coli and Enterococcus faecalis and the performance of immobilized A. junii in the same type of wastewater. In the sterilized wastewater which contained the mixture of A. junii, E. coli and E. faecalis, the A. junii was selectively immobilized onto NZ in significantly higher numbers than E. coli and E. faecalis. The A. junii added in the form of bioparticles to the wastewater containing E. coli and E. faecalis, multiplied and removed P from wastewater. The P removal from wastewater was a function of biomass of P-accumulating bacteria and not the amount of NZ or bioparticles used. The performance of A. junii was significantly better in membrane filtered than in autoclaved wastewater. The experiments that were performed in raw non sterilized wastewater showed that A. junii can be successfully immobilized onto NZ in competition with natively present heterotrophic bacteria, retain its metabolic activity and successfully remove P from such water, which makes this technology feasible from biotechnological aspect.

The effect of mineral carrier composition on phosphate-accumulating bacteria immobilization.

The goal of this study was to determine the dynamics and yield of immobilization of the phosphate-accumulating bacterium Acinetobacter junii on mineral carriers. As mineral carriers natural clinoptilolite tuff from Turkey (T) and Serbia (S) and natural bentonite (TER), in original and magnesium (Mg)-exchanged form were used. The key feature which determined the extent of immobilization of A. junii was the type of carrier; the immobilization yield decreased in order T>TER>S. The number of immobilized cells was significantly higher for the Mg-exchanged carriers when compared to their original counterparts (95 and 75 x 10(8)CFU g(-1) for T, 74 and 58 x 10(8)CFU g(-1) for TER, 19 and 6 x 10(8)CFU g(-1) for S). The Mg-exchanged T and S displayed a prolonged biofilm growth up to 24h, while the original counterparts reached the mature biofilm after 12h of incubation. Both forms of TER reached the mature biofilm after 24h of incubation, due to swelling property of the material. The number of immobilized cells correlated significantly negatively with particle size of the carrier, indicating that particle size is another important feature which determined the extent of immobilization. The Mg-exchange of original carriers resulted in significant increase of the zeta potential. When all of the materials were compared, the increase of the zeta potential of carriers correlated negatively with the number of immobilized cells, suggesting that the zeta potential of material is not a crucial factor which determined the immobilization of cells.