title: Endurance of methanogenic archaea in anaerobic bioreactors treating oleate-based wastewater.
abstract: Methanogenic archaea are reported as very sensitive to lipids and long chain fatty acids (LCFA). Therefore, in conventional anaerobic processes, methane recovery during LCFA-rich wastewater treatment is usually low. By applying a start-up strategy, based on a sequence of step feeding and reaction cycles, an oleate-rich wastewater was efficiently treated at an organic loading rate of 21 kg COD m(-3) day(-1) (50 % as oleate), showing a methane recovery of 72 %. In the present work, the archaeal community developed in that reactor is investigated using a 16S rRNA gene approach. This is the first time that methanogens present in a bioreactor converting efficiently high loads of LCFA to methane are monitored. Denaturing gradient gel electrophoresis profiling showed that major changes on the archaeal community took place during the bioreactor start-up, where phases of continuous feeding were alternated with batch phases. After the start-up, a stable archaeal community (similarity higher than 84 %) was observed and maintained throughout the continuous operation. This community exhibited high LCFA tolerance and high acetoclastic and hydrogenotrophic activity. Cloning and sequencing results showed that Methanobacterium- and Methanosaeta-like microorganisms prevailed in the system and were able to tolerate and endure during prolonged exposure to high LCFA loads, despite the previously reported LCFA sensitivity of methanogens.
authors.affiliation: Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Andreia F
authors.initials: AF
authors.lastname: Salvador
authors.forename: Ana J
authors.initials: AJ
authors.lastname: Cavaleiro
authors.forename: Diana Z
authors.initials: DZ
authors.lastname: Sousa
authors.forename: M Madalena
authors.initials: MM
authors.lastname: Alves
authors.forename: M Alcina
authors.initials: MA
authors.lastname: Pereira
mesh_terms: D001105:Archaea / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D058448:Biota; D016000:Cluster Analysis; D019641:DNA, Archaeal / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D058645:Denaturing Gradient Gel Electrophoresis; D008697:Methane / Q000378:metabolism*; D008969:Molecular Sequence Data; D019301:Oleic Acid / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D062065:Wastewater / Q000382:microbiology*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D019641:DNA, Archaeal; D004275:DNA, Ribosomal; D008697:Methane; D019301:Oleic Acid; D012336:RNA, Ribosomal, 16S; D062065:Wastewater; D014874:Water Pollutants, Chemical