title: Evaluating the potential impact of proton carriers on syntrophic propionate oxidation.
abstract: Anaerobic propionic acid degradation relies on interspecies electron transfer (IET) between propionate oxidisers and electron acceptor microorganisms, via either molecular hydrogen, formate or direct transfers. We evaluated the possibility of stimulating direct IET, hence enhancing propionate oxidation, by increasing availability of proton carriers to decrease solution resistance and reduce pH gradients. Phosphate was used as a proton carrying anion, and chloride as control ion together with potassium as counter ion. Propionic acid consumption in anaerobic granules was assessed in a square factorial design with ratios (1:0, 2:1, 1:1, 1:2 and 0:1) of total phosphate (TP) to Cl(-), at 1X, 10X, and 30X native conductivity (1.5 mS.cm(-1)). Maximum specific uptake rate, half saturation, and time delay were estimated using model-based analysis. Community profiles were analysed by fluorescent in situ hybridisation and 16S rRNA gene pyrosequencing. The strongest performance was at balanced (1:1) ratios at 10X conductivity where presumptive propionate oxidisers namely Syntrophobacter and Candidatus Cloacamonas were more abundant. There was a shift from Methanobacteriales at high phosphate, to Methanosaeta at low TP:Cl ratios and low conductivity. A lack of response to TP, and low percentage of presumptive electroactive organisms suggested that DIET was not favoured under the current experimental conditions.
authors.affiliation: The University of Queensland, Advanced Water Management Centre, St. Lucia, QLD 4072, Australia.
authors.forename: Natacha M S
authors.initials: NM
authors.lastname: Juste-Poinapen
authors.affiliation: The University of Queensland, School of Agriculture and Food Sciences, St. Lucia, QLD 4072, Australia.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Turner
authors.affiliation: Ghent University, Laboratory of Microbial Ecology and Technology (LabMET), 9000 Ghent, Belgium.
authors.forename: Korneel
authors.initials: K
authors.lastname: Rabaey
authors.affiliation: The University of Queensland, Advanced Water Management Centre, St. Lucia, QLD 4072, Australia.|The University of Queensland, Centre for Microbial Electrochemical Systems, St. Lucia, QLD 4072, Australia.
authors.forename: Bernardino
authors.initials: B
authors.lastname: Virdis
authors.affiliation: The University of Queensland, Advanced Water Management Centre, St. Lucia, QLD 4072, Australia.
authors.forename: Damien J
authors.initials: DJ
authors.lastname: Batstone
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D010084:Oxidation-Reduction; D011422:Propionates / Q000378:metabolism*; D018892:Proton-Motive Force / Q000187:drug effects*; D011522:Protons
chemical_list: D011422:Propionates; D011522:Protons