Caracterização de comunidades bacterianas mesófilas e termófilas em biorreatores a membrana durante o tratamento de efluentes de fábrica de papel reciclado / Characterization of mesophilic and thermophilic bacterial communities in membrane bioreactors during treatment of recycled paper mill effluents

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Paper mils consume large quantities of water and thus generate high volume of effluents. Biological treatment of paper mils industrial effluent is widely used for this purpose. The new technology of membrane bioreactors under thermophilic conditions is still underused due to the lack of sufficient technical and scientific knowledge. In spite of their importance, only a fraction of the microbial species found during the biological treatment of industrial effluents have been identified and described. In the present study, the technical feasibility of membrane bioreactors for themophilic and mesophilic treatments of recycled paper mill effluents was assessed. Bacterial communities present under those conditions were characterized. Three bioreactors were maintained: one at 35C, and two under gradually increasing temperatures, beginning at 35C up to 55C. To one of the latter bioreactors, upon reaching 55C, a sample of compost was added as a source of themophilic bacteria. Membrane bioreactors under thermophilic or mesophilic conditions were efficient for treating the recycled paper mill effluents, however, compost addition did not change the thermophilic treatment efficiency. The diversity among the bacterial population was evaluated by PCR-DGGE performed with metagenomic DNA extracted from biological sludge samples collected from the bioreactors at 35C, 40C, 45C, 50C, and 55C. Primers specific for Eubacteria, Firmicutes, Alphaproetobacteria, Betaproteobacteria, and Gamaproteobacteria were used. Different DGGE profiles were obtained at the different temperatures, implying bacterial communities composition changes for Eubateria, Firmicutes, Alphaproteobacteria, Betaproteobacteria, and Gamaproteobacteria. Compost addition to one reactor under thermophilic condition caused changes in the bacterial community. Partial sequencing of 16S rDNA revealed 20 unique DNA sequences belonging to Eubacteria present in the biological sludge kept under mesophilic condition (35C). Among them, 15% were Alphaproteobacteria, 15% Betaproteobacteria, 25% Firmicutes, and 45% could not be assigned to any recognized group.Twenty-two unique partial rDNA sequences were found on samples of the biological sludge kept at 45C. They represented 27.3% Alphaproteobacteria, 13.6% Betaproteobacteria, 31.8% Firmicutes, 4.5% Deinococcus-Thermus, and 4.5% Chlorobi. Eighteen percent of the sequences were not identified. From the bioreactor kept at 55C, 24 unique sequences were found: 4 % were Alphaproteobacteria, 20% Betaproteobacteria, 4 % Gamaproteobacteria, 40% Firmicutes, 12% Deinococcus-Thermus, and 4% Chlorobi, and 16% were not of any recognizable group. The results show that biological sludge, during the thermophilic treatment of recycled paper mill effluents display bacterial communities of similar diversity when compared to those of the mesophilic treatment. It is reasonable to conclude that membrane bioreactors under thermophilic conditions may be a feasible alternative for the treatment of recycled paper mill effluents, capable of maintaining bacterial communities diverse enough to efficiently remove the organic matter.

ASSUNTO(S)

diversidade bacteriana dgge metagenômica clonagem sequenciamento microbiologia aplicada dgge bacterial diversity cloning sequencing

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