Abstract Biological acid mine drainage treatment depends significantly on inoculum origin, pH, COD/sulfate ratio, and carbon source. In this study, the performance and microbial diversity of anaerobic batch reactors used for sulfate reduction was evaluated. A medium COD/sulfate ratio of 1.14 ± 0.10 was used, and the evaluation was performed in two steps: Phase 1, based on the inoculum source (autochthonous, AUT, and non-autochthonous, N-AUT); and Phase 2, based on the carbon source (lactate, ethanol, and formate) and low pH. In Phase 1, the sulfate removal using both AUT and N-AUT biomasses were similar, 53% and 59%, respectively. In Phase 2, ethanol and lactate as electron donors yielded similar sulfate removal efficiencies of 42% and 44%, respectively, at neutral pH. When the initial pH was reduced from 4 to 3, sulfate removal using formate remained nearly constant at 34%, whereas it reduced from 43% to 30% with lactate, and dropped significantly from 18% to 7% with ethanol. Denaturing gradient gel electrophoresis analyses for sulfate-reducing bacteria revealed their presence in all samples. Microbial activity and sulfate removal obtained for AUT cultures indicated that they possess the potential for use in local acid mine drainage decontamination processes.

ABSTRACT The aim of this study was to isolate and characterize bacterial strains from bauxite residue in the southern region of Minas Gerais, Brazil, by 16S rRNA gene sequencing and biochemical assays. Bacillus cohnii, Bacillus pseudofirmus, and Bacillus clarkii were identified among the isolates. The isolates were able to use a wide range of carbon sources and to grow at NaCl concentrations of up to 10%, temperatures from 10 to 40 °C, and pH from 7 to 10.5, producing a wide variety of organic acids. This is the first report on microbial composition of bauxite residue in Brazil.

The goal of this research was to evaluate the biodegradation of diesel by a microbial consortium collected in a region close to distributors of fuel. The experiments were monitored by SPME-GC-FID and SPME-GC-MS. The consortium showed a high potential for production of biosurfactants, presenting an emulsification index of 53%. The consortium degraded completely n-alkanes, while dimethylnaphtalene, hepthyl-cyclohexane and 2,6,10-trimethyl-undecane were partially degraded and pristane was not degraded. From this consortium five strains were isolated and identified as Acinetobacter baumannii. Based on this initial investigation this consortium appears to be effective for bioremediation in Porto Velho - RO region.