Long-chain n-alkane biodegradation coupling to methane production in an enriched culture from production water of a high-temperature oil reservoir

Abstract

Paraffinic n-alkanes (C22-C30), crucial portions of residual oil, are generally considered to be difficult to be biodegraded owing to their general solidity at ambient temperatures and low water solubility, rendering relatively little known about metabolic processes in different methanogenic hydrocarbon-contaminated environments. Here, we established a methanogenic C22-C30 n-alkane-degrading enrichment culture derived from a high-temperature oil reservoir production water. During two-year incubation (736 days), unexpectedly significant methane production was observed. The measured maximum methane yield rate (164.40 μmol L −1 d −1) occurred during the incubation period from day 351 to 513. The nearly complete consumption (> 97%) of paraffinic n-alkanes and the detection of dicarboxylic acids in n-alkane-amended cultures indicated the biotransformation of paraffin to methane under anoxic condition. 16S rRNA gene analysis suggested that the dominant methanogen in n-alkane-degrading cultures shifted from Methanothermobacter on day 322 to Thermoplasmatales on day 736. Bacterial community analysis based on high-throughput sequencing revealed that members of Proteobacteria and Firmicutes exhibiting predominant in control cultures, while microorganisms affiliated with Actinobacteria turned into the most dominant phylum in n-alkanedependent cultures. Additionally, the relative abundance of mcrA gene based on genomic DNA significantly increased over the incubation time, suggesting an important role of methanogens in these consortia. This work extends our understanding of methanogenic paraffinic n-alkanes conversion and has biotechnological implications for microbial enhanced recovery of residual hydrocarbons and effective bioremediation of hydrocarbon-containing biospheres.

Physiological and Genomic Characterization of Actinotalea subterranea sp. nov. from Oil-Degrading Methanogenic Enrichment and Reclassification of the Family Actinotaleaceae

“…The biogeochemical processes of anaerobic transformation of oil with methane generation in reservoirs nor containing sulfate in waters or with hydrogen sulfide generation in reservoirs with sulfate-containing waters are well documented [1,7,10,86].…”

“…Gram staining was performed by using a Gram staining kit (Biovitrum, Saint-Petersburg, Russia) according to the manufacturer's instructions. Growth at different temperatures (5,10,15,23,28,37, and 42 °C) was determined in the liquid R2A medium containing 2.0% (w/v) NaCl after incubation for 5-15 days. Salinity optimum and ranges for growth were determined in the liquid R2A medium containing 0, 0.1, 0.5, 1.0, 1.5, 2, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0% (w/v) NaCl for 7 days at 28 °C.…”

“…Kuznetsov [4]. A wide range of works is devoted to the study of the composition of methanogenic syntrophic associations degrading oil [5][6][7][8][9][10]. The participation of bacteria of the Syntrophaceae family in the syntrophic degradation of alkanes together with methanogens has been shown [11][12][13][14][15].…”

Anaerobic Degradation of Paraffins by Thermophilic Actinobacteria under Methanogenic Conditions

“…The cultures were set up as described before . In brief, incubations were set up with sterilized serum bottles (internal volume 120 mL), containing 40 mL of production water and 10 mL of autoclaved basal medium . No hydrocarbons were at detectable concentrations in the production water.…”

“…No hydrocarbons were at detectable concentrations in the production water. The basal medium was supplemented with 1 mL of trace elements, and 1 mL of vitamins stock solution as described previously . All incubations were set up in triplicates and incubated at 55 °C in the dark.…”