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Insight into the role of facultative bacteria stimulated by microaeration in continuous bioreactors converting LCFA to methane Maria Salomé Duarte, Sérgio A Silva, Andreia F Salvador, Ana Júlia Cavaleiro, Alfons J.M. Stams, Maria Madalena Alves, and Maria Alcina Pereira Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.8b00894 • Publication Date (Web): 15 May 2018 Downloaded from http://pubs.acs.org on May 17, 2018
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Environmental Science & Technology
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Insight into the role of facultative bacteria
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stimulated by micro-aeration in continuous
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bioreactors converting LCFA to methane
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M. Salomé Duarte1, Sérgio A. Silva1, Andreia F. Salvador1, Ana J. Cavaleiro1, Alfons J.
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M. Stams1,2, M. Madalena Alves1 and M. Alcina Pereira1,*
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1
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Braga, Portugal
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2
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Wageningen, The Netherlands
Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057
Laboratory of Microbiology, Wageningen University, Stippeneng 4, 6708 WE
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1 ACS Paragon Plus Environment
Environmental Science & Technology
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ABSTRACT
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Conversion of unsaturated long chain fatty acids (LCFA) to methane in continuous
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bioreactors is not fully understood. Palmitate (C16:0) often accumulates during oleate
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(C18:1) biodegradation in methanogenic bioreactors, and the reason why this happens
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and which microorganisms catalyze this reaction remains unknown. Facultative
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anaerobic bacteria are frequently found in continuous reactors operated at high LCFA
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loads, but their function is unclear. To get more insight on the role of these bacteria,
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LCFA conversion was studied under microaerophilic conditions. For that, we compared
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bioreactors treating oleate-based wastewater (organic loading rates of 1 and 3 kg COD
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m-3 d-1), operated under different redox conditions (strictly anaerobic-AnR, -350 mV;
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microaerophilic-MaR, -250 mV). At the higher load, palmitate accumulated 7 times
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more in the MaR, where facultative anaerobes were more abundant, and only the
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biomass from this reactor could recover the methanogenic activity after a transient
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inhibition. In a second experiment, the abundance of facultative anaerobic bacteria,
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particularly Pseudomonas spp. (from which two strains were isolated), was strongly
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correlated (p0.05) to the observed in trial 1 in the same
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Periods, showing the consistency and robustness of the results. In periods III and IV
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(trial 1), a shift (p
