RESUMO
Biodegradation of phenolic compounds in bioreactors is well documented, but the changes in the bacterial populations dynamics during degradation were not that often. A glass bubble column used as reactor was inoculated with activated sludge, spiked with 2-chlorophenol, phenol and m-cresol after 28 days and maintained for an additional 56 days, while the 16S rRNA gene from metagenomic DNA was monitored. Proteobacteria (68.1%) dominated the inoculum, but the bacterial composition changed rapidly. The relative abundance of Bacteroidetes and Firmicutes decreased from 4.8 and 9.4 to <0.1 and 0.2% respectively, while that of Actinobacteria and TM7 increased from 4.8 and 2.0 to 19.2 and 16.1% respectively. Phenol application increased the relative abundance of Proteobacteria to 94.2% (mostly Brevundimonas 17.6%), while that of Bacteroidetes remained low (1.2%) until day 42. It then increased to 47.3% (mostly Leadbetterella 46.9%) at day 84. It was found that addition of phenolic compounds did not affect the relative abundance of the Alphaproteobacteria initially, but it decreased slowly while that of the Bacteroidetes increased towards the end.
Assuntos
Bactérias/efeitos dos fármacos , Bactérias/metabolismo , Biodegradação Ambiental , Reatores Biológicos , Consórcios Microbianos/efeitos dos fármacos , Fenóis/metabolismo , Fenóis/farmacologia , Esgotos/microbiologia , Actinobacteria/classificação , Actinobacteria/efeitos dos fármacos , Actinobacteria/genética , Actinobacteria/fisiologia , Bactérias/classificação , Bactérias/genética , Bacteroidetes/classificação , Bacteroidetes/efeitos dos fármacos , Bacteroidetes/genética , Bacteroidetes/fisiologia , Clorofenóis/metabolismo , Clorofenóis/farmacologia , Cresóis/metabolismo , Cresóis/farmacologia , Sequenciamento de Nucleotídeos em Larga Escala , Metagenômica , Consórcios Microbianos/genética , Consórcios Microbianos/fisiologia , Fenol/metabolismo , Fenol/farmacologia , Proteobactérias/classificação , Proteobactérias/efeitos dos fármacos , Proteobactérias/genética , Proteobactérias/fisiologia , RNA Ribossômico 16S , Esgotos/análiseRESUMO
We have developed a novel microrespirometric method to characterize the inhibitory effects due to heavy metals on activated sludge treatment. This method was based on pulse dynamic respirometry and involved the injection of several pulses of substrate and inhibitors, of increasing concentration. Furthermore, we evaluated the inhibitory effects of heavy metals (copper and zinc), substrate and biomass concentrations, and pH on activated sludge activity. While higher biomass concentrations counteracted the inhibitory effects of both copper and zinc, higher substrate concentrations predominantly augmented the inhibitory effect of copper but no significant change in inhibition by zinc was observed. pH had a clear but relatively small effect on inhibition, partially explained by thermodynamic speciation. We determined the key kinetic parameters; namely, the half saturation constant (K S ) and the maximum oxygen uptake rate (OUR max ). The results showed that higher heavy metal concentrations substantially decreased K S and OUR max suggesting that the inhibition was uncompetitive.