An electrogenic microbial community from the polluted Reconquista River as revealed by molecular and kinetic analysis

PRADOS MB; VAZQUEZ SC; LEZCANO M; PORZIONATO N; ZILIANI A; FERNANDEZ ALBANESI L; PASQUEVICH D; CURUTCHET G

Obregon

Simposio; 6ISEBE; 2018

With theaim of developing a bioelectrochemical system (BES) for the immobilization ofheavy metals from effluents, we selected an electrogenic consortium ofmicroorganisms from sediments of the highly polluted Reconquista river, BuenosAires, Argentina (presented at the 5ISEBE symposium). This consortium (RE480)developed a dense and thick biofilm over graphite rod electrodespotentiostatized at 480 mV vs Ag/AgCl, which served as the sole electronacceptor in the BES. In this work, we present the characterization of such consortium,with the purpose of establishing the operation parameters of the BES in whichthese microorganisms will be used. RE480 was grown on DSMZ 579 medium withacetate as electron donor and fumarate as electron acceptor. The ability ofRE480 to grow at different pH (4, 5, 7, 9 and 10) and temperatures (15, 20, 30,40 and 45°C), and the combination of them, was tested under anaerobiosis. Additionally,we tested glucose and pyruvate as electron donors, employing the same medium,at pH 7 and 30°C. For every culture condition, we measured cell growth byturbidimetry, gas composition by respirometry and infrared spectroscopy (FTIR),cell phenotype by differential staining and scanning electron microscopy. Thephylogeny of the RE480 was studied by 16S sequencing. Additionally, to isolatethe components of RE480, the microorganisms were grown in selective media underanaerobic (Postgate, DSMZ 579) or aerobic (PCA, TSI) conditions. The optimumgrowth temperature of the microbial consortium was 30°C, although growth wasobserved between 20-40°C, at a pH range between 6-9. No gases other that CO2were detected, suggesting the complete oxidation of the provided substrates.These parameters should be considered for the operation of the BES in additionof the possibility to use complex organic compounds, which could generate ahigher current yield. At least six genera were identified in consortium RE480dominated by Clostridium and Aeromonas, highlighting the presence of Shewanella,one of the best characterized electrogenic microorganisms so far. Thesemicroorganisms are facultative anaerobes and have a great potential for applicationin BES. Interestingly, our results show that the electrogenic species found inthe biofilm grow in community with other non-microorganisms, suggesting thatthis type of mixed biofilm structures could be more robust than those formed bya single species.