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

MARÍA BELÉN PRADOS; LESCANO, MARIELA I.; NATALIA PORZIONATO; LUISA FERNANDEZ; DANIEL PASQUEVICH; GUSTAVO CURUTCHET

Simposio; Sixth International Symposium on Environmental Biotechnology and Engineering; 2018

With the aim of developing a bioelectrochemical system (BES) for the immobilization of heavy metals from effluents, we selected an electrogenic consortium of microorganisms from sediments of the highly polluted Reconquista river, Buenos Aires, Argentina (presentedat the 5ISEBE symposium). This consortium (RE480) developed a dense and thick biofilm over graphite rod electrodes potentiostatized at 480 mV vs Ag/AgCl, which served as the sole electron acceptor 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 with acetate as electron donor and fumarate as electron acceptor. The ability of RE480 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 underanaerobiosis. 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 by turbidimetry, gas composition by respirometry and infrared spectroscopy (FTIR), cell phenotype by differential staining and scanning electron microscopy. The phylogeny of the RE480 was studied by 16S sequencing. Additionally, to isolate the components of RE480, the microorganisms were grown in selective media under anaerobic (Postgate, DSMZ 579) or aerobic (PCA, TSI) conditions. The optimum growth temperature of the microbial consortium was 30°C, although growth was observed between 20-40°C, at a pH range between 6-9. No gases other that CO 2 were detected, suggesting the complete oxidation of the provided substrates . These parameters should be considered for the operation of the BES in addition of the possibility to use complex organic compounds, which could generate a higher current yield. At least six genera were identified in consortium RE480 dominated by Clostridium and Aeromonas, highlighting the presence of Shewanella, one of the best characterized electrogenic microorganisms so far. These microorganisms are facultative anaerobes and have a great potential for application in BES. Interestingly, our results show that the electrogenic species found in the biofilm grow in community with other non-microorganisms, suggesting that this type of mixed biofilm structures could be more robust than those formed by a single species.