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Progressive degradation of crude oil n-alkanes coupled to methane production under mesophilic and thermophilic conditions.

Cheng L, Shi S, Li Q, Chen J, Zhang H, Lu Y - PLoS ONE (2014)

Bottom Line: 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.

View Article: PubMed Central - PubMed

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.

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.

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Time course of methane production at different temperatures.A: 35°C; B: 55°C. Arrows indicate sampling points for construction of clone libraries. • and ▴: Cultures were grown in triplicate, error bars represent the standard deviation. ▪: Cultures were grown in duplicate, error bars represent the standard deviation.
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pone-0113253-g001: Time course of methane production at different temperatures.A: 35°C; B: 55°C. Arrows indicate sampling points for construction of clone libraries. • and ▴: Cultures were grown in triplicate, error bars represent the standard deviation. ▪: Cultures were grown in duplicate, error bars represent the standard deviation.

Mentions: The pre-enrichment cultures accumulated methane consecutively at 35 and 55°C (Fig. S1 in File S1), indicating that the oily sludge microbes could grow at both temperatures. To further confirm methanogenic degradation of crude oil, the pre-enrichment cultures were subcultured and incubated at the same pre-enrichment temperature. The mesophilic culture (35°C), amended with crude oil, produced 3.7±0.3 mmol of methane with a maximum specific methane production rate of 0.01 mmol.d−1 after 453 days of incubation (Fig. 1A). The thermophilic consortium (55°C), amended with the same amount of crude oil, accumulated 2.8±0.3 mmol of methane after 389 days of incubation with maximum specific methane production rate of 0.02 mmol.d−1 (Fig. 1B). Less than 0.2 mmol methane was produced by the crude oil-free cultures at either temperature, and no methane was detected in the abiotic control.


Progressive degradation of crude oil n-alkanes coupled to methane production under mesophilic and thermophilic conditions.

Cheng L, Shi S, Li Q, Chen J, Zhang H, Lu Y - PLoS ONE (2014)

Time course of methane production at different temperatures.A: 35°C; B: 55°C. Arrows indicate sampling points for construction of clone libraries. • and ▴: Cultures were grown in triplicate, error bars represent the standard deviation. ▪: Cultures were grown in duplicate, error bars represent the standard deviation.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4237390&req=5

pone-0113253-g001: Time course of methane production at different temperatures.A: 35°C; B: 55°C. Arrows indicate sampling points for construction of clone libraries. • and ▴: Cultures were grown in triplicate, error bars represent the standard deviation. ▪: Cultures were grown in duplicate, error bars represent the standard deviation.
Mentions: The pre-enrichment cultures accumulated methane consecutively at 35 and 55°C (Fig. S1 in File S1), indicating that the oily sludge microbes could grow at both temperatures. To further confirm methanogenic degradation of crude oil, the pre-enrichment cultures were subcultured and incubated at the same pre-enrichment temperature. The mesophilic culture (35°C), amended with crude oil, produced 3.7±0.3 mmol of methane with a maximum specific methane production rate of 0.01 mmol.d−1 after 453 days of incubation (Fig. 1A). The thermophilic consortium (55°C), amended with the same amount of crude oil, accumulated 2.8±0.3 mmol of methane after 389 days of incubation with maximum specific methane production rate of 0.02 mmol.d−1 (Fig. 1B). Less than 0.2 mmol methane was produced by the crude oil-free cultures at either temperature, and no methane was detected in the abiotic control.

Bottom Line: 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.

View Article: PubMed Central - PubMed

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.

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.

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