Enhancement of methane production from 1‐hexadecene by additional electron donors

Abstract

Summary1‐Hexadecene‐contaminated wastewater is produced in oil refineries and can be treated in methanogenic bioreactors, although generally at low conversion rates. In this study, a microbial culture able to degrade 1‐hexadecene was enriched, and different stimulation strategies were tested for enhancing 1‐hexadecene conversion to methane. Seven and three times faster methane production was obtained in cultures stimulated with yeast extract or lactate, respectively, while cultures amended with crotonate lost the ability to degrade 1‐hexadecene. Methane production from 1‐hexadecene was not enhanced by the addition of extra hydrogenotrophic methanogens. Bacteria closely related to Syntrophus and Smithella were detected in 1‐hexadecene‐degrading cultures, but not in the ones amended with crotonate, which suggests the involvement of these bacteria in 1‐hexadecene degradation. Genes coding for alkylsuccinate synthase alpha‐subunit were detected in cultures degrading 1‐hexadecene, indicating that hydrocarbon activation may occur by fumarate addition. These findings are novel and show that methane production from 1‐hexadecene is improved by the addition of yeast extract or lactate. These extra electron donors may be considered as a potential bioremediation strategy of oil‐contaminated sites with bioenergy generation through methane production.

Insight into the Role of Facultative Bacteria Stimulated by Microaeration in Continuous Bioreactors Converting LCFA to Methane

“…Details on the sequencing and bioinformatics data analysis can be found elsewhere. 31 The FASTQ files were submitted in the ENA (European Nucleotide Archive), being available in the following link http://www.ebi.ac.uk/ena/data/ view/PRJEB11469. Nucleotide sequences from Experiment 1 are identified with accession numbers ERS937154 to ERS937157 and sequences from Experiment 2 with the accession numbers ERS1487522 to ERS1487524 and ERS1505407 for trial 1 and ERS2319672 to ERS2319677 for trial 2.…”

Long-Chain Fatty Acids Degradation by Desulfomonile Species and Proposal of “Candidatus Desulfomonile Palmitatoxidans”

“…Short-chain fatty acids (C2 to C6) were analyzed by liquid chromatography (HPLC) as described previously ( Paulo et al, 2018 ). MCFA and LCFA (C8 up to C18) were measured by gas chromatography (GC Varian 3800, Agilent, Santa Clara, CA, United States) after esterification with propanol and extraction with dichloromethane, as described by Neves et al (2009) .…”

“…Samples were collected with minimum contact with air, transferred to a zinc acetate solution (2% w/v) prepared with 0.2 ml/L of concentrated acetic acid, and immediately analyzed. Methane formation was measured by gas chromatography (Chrompack 9000) equipped with a FID detector, as described before ( Paulo et al, 2018 ). Halogenated benzoates and benzoate were analyzed by HPLC, with a Poroshell 120 EC-C18 column (Agilent, Santa Clara, CA, United States), using a three-step gradient profile consisting of: (i) 90% eluent A (0.1% formic acid in water) and 10% eluent B (0.1% formic acid in acetonitrile) for 2 min, (ii) 90–20% eluent A and 10–80% eluent B for 14 min and hold at 20% eluent A and 80% eluent B for 3 min, (iii) followed by 20–90% eluent A and 80–10% eluent B for 1 min.…”

Co‐cultivation of Thermoanaerobacter strains with a methanogenic partner enhances glycerol conversion

“…Samples were amplified for sequencing using the universal primer pair 515f and 806r (Caporaso et al, 2011), targeting the prokaryotic 16S rRNA gene. Details on the sequencing and bioinformatics data analysis can be found elsewhere (Paulo et al, 2017). All sequencing reads were submitted to the European Nucleotide Archive (ENA) under the study accession number PRJEB30535 (http://www.eb i.ac.uk/ena/data/view/PRJEB30535).…”