Microbial community characteristics of petroleum reservoir production water amended with n-alkanes and incubated under nitrate-, sulfate-reducing and methanogenic conditions

Abstract

Methanogenic, sulfate- and nitrate-reducing enrichment cultures amended with long-chain n-alkanes (C 15-C 20) were established with production water from Huabei oilfield in China in the present study. Chemical analyses indicated that degradation of n-alkanes was evident under all three conditions after 356 days of incubation. Phylogenetic analyses based on 16S rRNA gene amplification indicated that α-, β-, γ-Proteobacteria and Bacteroidetes were detected in the nitrate-reducing enrichment; Actinobacteria, Nitrospira and δ-Proteobacteria were recovered from both the sulfate-reducing and methanogenic enrichments. Actinobacteria and Nitrospira were the most abundant in methanogenic and sulfate-reducing enrichment, respectively. The archaeal clone libraries showed that the order Methanomicrobiales within the phylum Euryarchaeota predominated methanogenic enrichment; whereas the unclassified class Thermoprotei within the phylum Crenarchaeota prevailed in sulfate-reducing enrichment. Comparison of 16S rRNA gene sequences from genomic DNA extracted directly from the petroleum reservoir production water with those from the three active enrichments showed that the available electron acceptors had a strong influence on the microbial community composition. In addition, genes encoding the alkylsuccinate synthase (assA) and methyl coenzyme-M reductase (mcrA) were amplified from the methanogenic enrichment and the results suggested that fumarate addition was probably involved in the degradation of n-alkanes. These results shed light on the potential utilization of microbial metabolism in remediation of hydrocarbon contamination or in enhancing the recovery of residual oil for energy. © 2012 Elsevier Ltd.