The metallurgic wastewater generated from the processes of recovering precious metals from industrial wastes contains high concentrations of nitrogen compounds and salts. Biological nitrogen removal from this wastewater was attempted using a circulating bioreactor system equipped with an anaerobic packed bed or an anaerobic fluidized bed. The denitrification capability of the system with the anaerobic packed bed was more stable than that of the system with the anaerobic fluidized bed. The NOx removal rate of the anaerobic packed bed was as high as 97%. Microbial community analysis by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA (rDNA) fragments and the cultivation method revealed that the community diversity varied in accordance with wastewater composition such as the level of salinity and so on. Phylogenetic analysis suggested that the taxonomic affiliation of the dominant species in the anaerobic reactors was to the gamma-Proteobacteria including Halomonadaceae species. The PCR-DGGE method as a non-cultivation method was found to be a powerful tool for analysis of the microbial community, because the cultivation method could detect only a fraction of the microbial species present in these systems. The genetic diversity of the isolated bacteria belonging to the gamma-Proteobacteria which reduced both nitrate and nitrite in the anaerobic packed bed was higher than that of the bacteria in the anaerobic fluidized bed. This suggested that a genetically diverse microbial community stabilized the denitrifying performance in the anaerobic packed bed.
Enzyme-linked immunosorbent assay (ELISA) by use of monoclonal antibodies (MAbs) is very useful and helpful for the detection and quantification of the specific bacteria like nitrifiers in a mixed bacterial habitat. In this study, seven monoclonal antibodies were raised from splenocytes of mice(BALB/c) that are specific for the surface antigen of the two kinds of nitrifying bacteria. Three were directed against Nitrosomonas europaea (IFO 14298) and four were directed against Nitrobacter winogradskyi (IFO 14297). Cross-reactivities of MAbs against other strains of nitrifying bacteria as well as some kinds of representative heterotrophic bacteria in activated sludge and biofilm were checked to determine the usefulness of MAbs. It was found that there were some strain specificities between the same genera of IFO and ATCC strain. By means of a competitive ELISA, correlation curves for quantifying nitrifying bacteria were developed in a pure culture. It was found that this monoclonal antibody method could be used as a quick and powerful tool for estimating and controlling the population of nitrifying bacteria.
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