Acetic acid formation by acetogens from hydrogen and CO2:dissolution of carbonates and competition by methanogens
Date
2014-07-11
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Abstract
Methane-producing archea (methanogens) and bacteria that produce acetic acid from H2 and CO2 (acetogens) exist in many low nutrient environments where other electron acceptors are absent. Methanogens usually outcompete acetogens because of a more powerful energy production but recent evidence suggests that acetogens may be able to compete through greater substrate diversity and energy efficiency (Lever 2012). Acetogenesis could be adapted as a biotechnology to induce carbonate dissolution in carbonate oil reservoirs.
Enrichments were conducted on the subsurface production waters from a conventional oil field. Variations in medium composition were tested to promote acetogenesis over methanogenesis. High levels of acetic acid of up to 2400 μmol or 28 mM were produced and the consumed along with various levels of methane. Analysis of 16S rRNA gene sequences show a progression from dominance of acetogenesis to methanogenesis and then a shift to a group of microbes that consume acetate to create biopolymers like polyhydroxybutyrate for storage of carbon in nutrient-limited environments. Factors that increase acetic acid production include ultra-low nutrient environments, sufficient pH buffering, not adding bicarbonate, and possibly increased surface area. Dissolution via microbial acetic acid was tested for powdered CaCO3, crushed and solid carbon rock but results are inconclusive.
Acetogens can be competitive with methanogens under the lowest nutrient conditions. The excess of the H2/CO2 energy and carbon substrates used in these experiments along with differences seen in nutrient variation suggest that conditions other than substrate availability can influence this competition. Sampling loss, re-precipitation and other experimental factors make carbonate dissolution mediated by microbial acetic acid difficult to track.
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Keywords
Ecology, Microbiology, Biogeochemistry
Citation
Rollick, L. (2014). Acetic acid formation by acetogens from hydrogen and CO2:dissolution of carbonates and competition by methanogens (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/24657