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.

Determination of Microbial Maintenance in Acetogenesis and Methanogenesis by Experimental and Modeling Techniques

“…A literature survey (Supplementary Table S2, Supplementary Material A) provides first hints on which of the taxa might be responsible for VFA oxidation and which ones might be responsible for degradation of dead microbial biomass. Cloacimonetes (Pelletier et al, 2008; Juste-Poinapen et al, 2015; Ahlert et al, 2016), Cryptanaerobacter (de Bok et al, 2005), and Desulfovibrio (Suzuki et al, 2010) have been connected with propionic or butyric acid oxidation but no co-culture of one of their species with a hydrogenotrophic methanogen has been tested yet. Candidatus Cloacamonas acidaminovorans, for example, contains all genes for propionic acid oxidation via methylmalonyl-CoA but has not been isolated yet (Pelletier et al, 2008).…”

Enhancing methane production from food waste fermentate using biochar: the added value of electrochemical testing in pre-selecting the most effective type of biochar

“…DIET in syntrophic methanogenic cultures, that is solely based on biological electrical connections, has been documented in co-cultures of Geobacter species [ 11 , 12 ] as well as in co-cultures of Geobacter metallireducens with Methanosaeta harundinacea [ 13 ] or Methanosarcina barkeri [ 14 ] and in co-cultures of Geobacter hydrogenophilus and Methanosarcina barkeri [ 15 ]. DIET based on biological connections has been documented also in anaerobic granules and methanogenic wastewater digester aggregates [ 16 , 17 ].…”

Dynamic functional characterization and phylogenetic changes due to Long Chain Fatty Acids pulses in biogas reactors

“…Focusing on the gene content of Pr01, a possible explanation for this finding could be ascribed to the quinone-mediated interspecies electron transfer. It is well known that the interspecies electron transfer is a fundamental feature in syntrophic communities between anaerobic bacteria and archaea 33 34 . To maintain the redox reactions of LCFA degradation at sufficiently exergonic levels, syntrophic bacteria deposit electrons onto hydrogen, which will be in turn utilized by methanogens to produce methane.…”