Resumo

Autotrophic and mixotrophic denitrifying microorganisms can be applied to remove sulfur and nitrate compounds from wastewater. In this study clone library was used to access the microbial community from anoxic chamber of a pilot scale bioreactor treating real sewage and designed for the occurrence of anaerobic, nitrifying and denitryfing processes. The denitryfing metabolism occurred inside the anoxic chamber using endogenous electron donors, such as sulfur reduced compounds, from the anaerobic metabolism. Genomic DNA was extracted from biofilm samples and clone library of the 16S rRNA gene was done. A total of 68 clones were analysed and the results showed sequences related to the Phylum Proteobacteria (45%) followed by Verrucomicrobia(15%),Synergistes (14%),Bacterioidetes (5%) and Firmicutes(5%).Unclassified sequences comprised 16% of the clone library. The predominance of clones related to Proteobacteria shows the presence of denitrifiers with detection of clones related to Pseudomonadaceae, Hilocbacteriaceae and Methylophilacaeae in similar proportions (8-9%). The clones related to Pseudomonas sp, Arcobacter sp and Sulfuricurvum kujiense, may indicate the role of these organisms in mixotrophic and strictly sulfur-autotrophic denitrification. Clones related to the family Methylophilacaeae were also observed indicating the occurrence of heterotrophic denitrification. Clones related Desulfomonadaceae and Desulfovibrionaceae comprised both 24% of the Phylum Proteobacteria and their presence may indicate the occurrence of microniches for sulfate reducing metabolism. Clones related to the Phyla Clostridia(Clostridium sp) and Synergistetes, with detection of uncultured Synergistes and Aminanaerobia, indicate the presence of fermentative metabolism using organic residuals from the anaerobic chamber. We can conclude that the microbial community developed inside the anoxic chamber was complex with detection of clones related to mixotrophic and strictly autotrophic denitrifiers as well as sulfate reducing bacteria and microorganisms with fermentative metabolism, which indirectly may have participated of denitrification by providing the denitrifiers with electron donors.