title: Conversion of Cn-Unsaturated into Cn-2-Saturated LCFA Can Occur Uncoupled from Methanogenesis in Anaerobic Bioreactors.
abstract: Fat, oils, and grease present in complex wastewater can be readily converted to methane, but the energy potential of these compounds is not always recyclable, due to incomplete degradation of long chain fatty acids (LCFA) released during lipids hydrolysis. Oleate (C18:1) is generally the dominant LCFA in lipid-containing wastewater, and its conversion in anaerobic bioreactors results in palmitate (C16:0) accumulation. The reason why oleate is continuously converted to palmitate without further degradation via β-oxidation is still unknown. In this work, the influence of methanogenic activity in the initial conversion steps of unsaturated LCFA was studied in 10 bioreactors continuously operated with saturated or unsaturated C16- and C18-LCFA, in the presence or absence of the methanogenic inhibitor bromoethanesulfonate (BrES). Saturated Cn-2-LCFA accumulated both in the presence and absence of BrES during the degradation of unsaturated Cn-LCFA, and represented more than 50% of total LCFA. In the presence of BrES further conversion of saturated intermediates did not proceed, not even when prolonged batch incubation was applied. As the initial steps of unsaturated LCFA degradation proceed uncoupled from methanogenesis, accumulation of saturated LCFA can be expected. Analysis of the active microbial communities suggests a role for facultative anaerobic bacteria in the initial steps of unsaturated LCFA biodegradation. Understanding this role is now imperative to optimize methane production from LCFA.
authors.affiliation: Centre of Biological Engineering, University of Minho , Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Ana J
authors.initials: AJ
authors.lastname: Cavaleiro
authors.affiliation: Centre of Biological Engineering, University of Minho , Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Maria Alcina
authors.initials: MA
authors.lastname: Pereira
authors.affiliation: Centre of Biological Engineering, University of Minho , Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Ana P
authors.initials: AP
authors.lastname: Guedes
authors.affiliation: Centre of Biological Engineering, University of Minho , Campus de Gualtar, 4710-057 Braga, Portugal.|Laboratory of Microbiology, Wageningen University , Dreijenplein 10, 6703 HB Wageningen, The Netherlands.
authors.forename: Alfons J M
authors.initials: AJ
authors.lastname: Stams
authors.affiliation: Centre of Biological Engineering, University of Minho , Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: M Madalena
authors.initials: MM
authors.lastname: Alves
authors.affiliation: Centre of Biological Engineering, University of Minho , Campus de Gualtar, 4710-057 Braga, Portugal.|Laboratory of Microbiology, Wageningen University , Dreijenplein 10, 6703 HB Wageningen, The Netherlands.
authors.forename: Diana Z
authors.initials: DZ
authors.lastname: Sousa
mesh_terms: D017738:Alkanesulfonic Acids / Q000494:pharmacology; D000693:Anaerobiosis; D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D005227:Fatty Acids / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D008697:Methane / Q000378:metabolism*; D059013:Microbial Consortia / Q000187:drug effects; D019301:Oleic Acid / Q000378:metabolism*; D010168:Palmitates / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000295:instrumentation* / Q000379:methods
chemical_list: D017738:Alkanesulfonic Acids; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D010168:Palmitates; C018853:2-bromoethanesulfonic acid; D019301:Oleic Acid; D008697:Methane