Electroactive biofilms on surface functionalized anodes: the anode respiring behavior of a novel electroactive bacterium, Desulfuromonas acetexigens

Katuri, Krishna P.; Kamireddy, Sirisha; Kavanagh, Paul; Mohammad, Ali; Conghaile, Peter Ó; Kumar, Amit; Saikaly, Pascal E.; Leech, Dónal

Surface chemistry is known to influence the formation, composition and electroactivity of electron-conducting biofilms with however limited information on the variation of microbial composition and electrochemical response during biofilm development to date. Here we present voltammetric, microscopic and microbial community analysis of biofilms formed under fixed applied potential for modified graphite electrodes during early (90 h) and mature (340 h) growth phases. Electrodes modified to introduce hydrophilic groups (−NH2, −COOH and −OH) enhance early-stage biofilm formation compared to unmodified or electrodes modified with hydrophobic groups (−C2H5). In addition, early-stage films formed on hydrophilic electrodes were dominated by the gram-negative sulfur-reducing bacterium Desulfuromonas acetexigens while Geobacter sp. dominated on −C2H5 and unmodified electrodes. As biofilms mature, current generation becomes similar, and D. acetexigens dominates in all biofilms irrespective of surface chemistry. Electrochemistry of pure culture D. acetexigens biofilms reveal that this microbe is capable of forming electroactive biofilms producing considerable current density of > 9 A/m2 in a short period of potential induced growth (~19 h followed by inoculation) using acetate as an electron donor. The inability of D. acetexigens biofilms to use H2 as a sole source electron donor for current generation shows promise for maximizing H2 recovery in single-chambered microbial electrolysis cell systems treating wastewaters. Highlights Anode surface chemistry affects the early stage biofilm formation. Hydrophilic anode surfaces promote rapid start-up of current generation. Certain functionalized anode surfaces enriched the Desulfuromonas acetexigens. D. acetexigens is a novel electroactive bacteria. D. acetexigens biofilms can produce high current density in a short period of potential induced growth D. acetexigens has the ability to maximize the H2 recovery in MEC. TOC – Graphical abstract