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Front. Energy Res. | doi: 10.3389/fenrg.2018.00125

Concentration pulse method for the investigation of transformation pathways in a glycerol-fed bioelectrochemical system

 Fabian Kubannek1, Christopher Moß1, Katharina Huber2,  Joerg Overmann2,  Uwe Schröder1 and  Ulrike Krewer1*
  • 1Institute of Energy and Process Systems Engineering, Technische Universitat Braunschweig, Germany
  • 2Diversity Research, Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ), Germany

We investigated transformation pathways and determined rate constants in a continuously operated glycerol-fed bioelectrochemical system under chemostatic conditions by applying concentration pulses of various intermediates. Our methodology does not require the interruption of the continuous operation and is thus in principle suitable for elucidating processes in continuously operated bioreactors in industry as well as in laboratory studies.
Specifically for the example of glycerol electrooxidation, pulse responses of current density and effluent concentrations reveal that glycerol is first fermented to acetate, which is then oxidized electrochemically by the anode respiring bacteria.
Microbial community analysis confirms this division of labour with a bioanode dominated by Geobacter species 92.8 %) and a much more diverse fermenting community in the planktonic phase, containing mainly Desulfovibrio sp. (45.2 %) and Spiroaetales (18.1 %). Desulfovibrio and Geobacter species are identified as promising candidates for tailored communities for glycerol electro-oxidation.
From an acetate concentration pulse experiment, growth rates and half saturation rate constants for the biofilm of K_S = 1.4 mol m^-3 and d(q_{max,Ac} X_{bf})/dt = 933 mmol m^-2 d^-2 are obtained.
Furthermore, 1,3-propanediol and glycerol concentration pulse experiments show that the reaction from glycerol to 1,3-propanediol is reversed at high 1,3-propanediol concentrations.
The presented methodology allows one to study pathways and extract rate constants through simple experiments in a running system without irreversibly altering the microbial community or destroying the biofilm.

Keywords: Concentration pulse method, bioelectrochemical system, Microbial fuel cell (MFC), Biofilm kinetics, Anaerobic digestion (AD), Glycerol utilization

Received: 27 Aug 2018; Accepted: 06 Nov 2018.

Edited by:

Boris Tartakovsky, National Research Council Canada (NRC-CNRC), Canada

Reviewed by:

Miriam A. Rosenbaum, Leibniz-Institut für Naturstoff-Forschung und Infektionsbiologie, Hans Knöll Institut, Germany
Yong Xu, Nanjing Forestry University, China  

Copyright: © 2018 Kubannek, Moß, Huber, Overmann, Schröder and Krewer. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Ulrike Krewer, Technische Universitat Braunschweig, Institute of Energy and Process Systems Engineering, Braunschweig, Germany, u.krewer@tu-braunschweig.de