title: Progressive degradation of crude oil n-alkanes coupled to methane production under mesophilic and thermophilic conditions.
abstract: Although methanogenic degradation of hydrocarbons has become a well-known process, little is known about which crude oil tend to be degraded at different temperatures and how the microbial community is responded. In this study, we assessed the methanogenic crude oil degradation capacity of oily sludge microbes enriched from the Shengli oilfield under mesophilic and thermophilic conditions. The microbial communities were investigated by terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA genes combined with cloning and sequencing. Enrichment incubation demonstrated the microbial oxidation of crude oil coupled to methane production at 35 and 55°C, which generated 3.7±0.3 and 2.8±0.3 mmol of methane per gram oil, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that crude oil n-alkanes were obviously degraded, and high molecular weight n-alkanes were preferentially removed over relatively shorter-chain n-alkanes. Phylogenetic analysis revealed the concurrence of acetoclastic Methanosaeta and hydrogenotrophic methanogens but different methanogenic community structures under the two temperature conditions. Candidate divisions of JS1 and WWE 1, Proteobacteria (mainly consisting of Syntrophaceae, Desulfobacteraceae and Syntrophorhabdus) and Firmicutes (mainly consisting of Desulfotomaculum) were supposed to be involved with n-alkane degradation in the mesophilic conditions. By contrast, the different bacterial phylotypes affiliated with Caldisericales, "Shengli Cluster" and Synergistetes dominated the thermophilic consortium, which was most likely to be associated with thermophilic crude oil degradation. This study revealed that the oily sludge in Shengli oilfield harbors diverse uncultured microbes with great potential in methanogenic crude oil degradation over a wide temperature range, which extend our previous understanding of methanogenic degradation of crude oil alkanes.
authors.affiliation: College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China; Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture, Chengdu, 610041, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Cheng
authors.affiliation: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing, 102200, China.
authors.forename: Shengbao
authors.initials: S
authors.lastname: Shi
authors.affiliation: Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture, Chengdu, 610041, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.affiliation: State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing, 102200, China.
authors.forename: Jianfa
authors.initials: J
authors.lastname: Chen
authors.affiliation: Key Laboratory of Development and Application of Rural Renewable Energy, Biogas Institute of Ministry of Agriculture, Chengdu, 610041, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
authors.forename: Yahai
authors.initials: Y
authors.lastname: Lu
mesh_terms: D000473:Alkanes / Q000378:metabolism*; D001105:Archaea / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism; D001419:Bacteria / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism; D008697:Methane / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D010578:Petroleum / Q000378:metabolism; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013696:Temperature
chemical_list: D000473:Alkanes; D010578:Petroleum; D012336:RNA, Ribosomal, 16S; D008697:Methane