Full Length Research Paper

Microbial community dynamics in diesel waste biodegradation using sequencing batch bioreactor operation mode (SBR)

Edelvio de Barros Gomes¹*, Flavia Lima do Carmo², Adriana Lopes², Raquel Silva Peixoto², Alexandre Soares Rosado² and Nei Pereira Jr.¹

¹Department of Biochemical Engineering, School of Chemistry, Laboratories of Bioprocess Development, Center of Technology - Federal University of Rio de Janeiro Rio de Janeiro - R.J. - Brazil - CEP 21949-900, Brazil.

²Laboratory of Molecular Microbial Ecology – Institute of Microbiology - Federal University of Rio de Janeiro Rio de Janeiro - R.J. - Brazil - CEP 2194902, Brazil.

*Corresponding author: E-mail: edelviogomes@gmail.com. Fax: ++ 55 (21) 2562 7567.

Abbreviations: SBR, Sequential batch bioreactor; CSTR, continuously stirred bioreactor; GC, gas chromatograph; FID, flame ionization detector; DGGE, denaturing gradient gel electrophoresis; PCR, polymerase chain reaction; OUR, oxygen uptake rates; DSS, dodecyl sodium sulfate.

Accepted 19 October, 2010

   Abstract

The dynamic of molecular microbial community during diesel waste biodegradation was investigated. The waste was treated in bioreactors operated in sequencing batch operation mode (SBR) in four cycles of 72 h, using optimized setpoints (pH, initial waste load, C:N ratio, aeration). Optimal conditions allowed the system to reach biodegradation of 53.3, 96.0, 76.2 and 75.0% at the end of cycles one, two three and four, respectively. Oxygen uptake rate (OUR) indicated increases in microbial activity from cycle one to cycle two (124.9 to 252.9 mgO₂/L/h) and decreases in cycles three and four (120.4 to 108.8 mgO₂/L/h_, respectively). Investigations of microbial diversity showed changes in the microbial community members at the end of the cycle one. Significant reductions in the relative ecotoxicity were observed beginning with cycle two, and the reductions extended until the end of process. The SBR operation mode proved to be an efficient method for treating the diesel waste, and the process allowed for relevant reductions in the hydrocarbon content of the waste along with an increase in its environmental quality. Changes in the microbial members are evidence of the synergistic action of the microbiota in the process.

Key words: Microbial diversity, denaturing gradient gel electrophoresis, sequencing batch, biodegradation.