Cultivating Electrochemically Active Biofilms at Continuously Changing Electrode Potentials

Abstract

In this study, electrochemically active microbial biofilms were cultivated and studied at continuously alternating electrode potentials. Compared to cultivation and operation at a single constant potential, this method enhanced microbial turnover and maximum current densities. Electrochemically active microbial biofilms were cultivated in a multi‐carbon source culture for several biofilm generations and were subsequently fed with real, domestic wastewater. Compared to constant potential cultivation, average (N=12) biofilm limiting current density at +0.2 V vs. Ag/AgCl increased from 0.350±0.101 to 0.508±0.099 mA cm−2 with a significant reduction in the time required until the maximum current output was reached from 2.01±0.79 to 1.36±0.71 d. The relative increase in maximum current density and decrease in the time required to reach it are similar. The relative differences of higher over lower values are both approximately 45 %. Biofilm community analysis showed a dominance of Geobacteraceae spp. in the electrochemically active biofilms, which is in accordance with the formal potentials derived from cyclic voltammetry. The overall increase in performance is related to the selection of electrochemically active microorganisms, which exhibit local maxima in their electron transfer kinetics between −0.3 and −0.2 V vs. Ag/AgCl.

Developing Cheap and Mass‐Producible Graphite‐Filled Paper as an Anode Material for Microbial Electrochemical Technologies

“…In practice MET need to achieve high substrate turnovers and current densities at the lowest possible (over‐)potentials, because the combination of these parameters determines their viability . Initially, all electrodes were studied using acetate as the only substrate, which led to the development of typical red‐colored biofilms, see Figure SI‐2.…”

Investigating Community Dynamics and Performance During Microbial Electrochemical Degradation of Whey

“…An example of the reactor setup is shown in the SI 2 in Figure S1. A triplicate of reactors (R1–R3) were operated at anode potentials of 0.2 V vs. Ag/AgCl, another triplicate (R4–R6) at 0 V and lastly a triplicate (R7–R9) at −0.2 V. These values were chosen because in a previous study, the beginning of plateaus in bioelectrochemical activity (∼current density) were observed between −0.2 V and 0 V vs. Ag/AgCl. The cell voltage required to maintain the anode potentials is applied by the potentiostat.…”

“…[9][10][11][12][13] In the recent years significant progress has been made in improving the maximum current densities and turnover rates to 0.034 mA cm À 2 [11] at technical scale. Further the current density was improved to 0.35 mA cm À 2 [14] by developing new cultivation media based on the composition of hydrolysis/fermentation products and to 0.51 mA cm À 2 [15] by forcing the development of energy efficient EAB mixed culture biofilms. In both aforementioned studies, the individual procedural improvements were accompanied by repetitions of biofilm harvesting from the best performing bioanode/reactor and re-inoculation into fresh reactors.…”

“…The two central objectives of this study are: i) to investigate the capability of MET to degrade and harvest electrons from a whey solution with an initial COD concentration of 1048±25.5 mg O 2 L −1 , as a model substitute for real dairy WW from which the whey has not been separated. Also and in contrast to previous studies, in which microbial analysis was only performed at the end of the experiments, it is the objective ii) to investigate the effect of the selection and re‐inoculation on the development of the microbial communities at the bioanodes and in the reactor volume. The potential applied ( E app ) to a bioanode is important, with regard to energy efficiency, three different E app were studied, in order to analyze its effect on their performance and the microbial community development.…”

“…Also and in contrast to previous studies, in which microbial analysis was only performed at the end of the experiments, it is the objective ii) to investigate the effect of the selection and re‐inoculation on the development of the microbial communities at the bioanodes and in the reactor volume. The potential applied ( E app ) to a bioanode is important, with regard to energy efficiency, three different E app were studied, in order to analyze its effect on their performance and the microbial community development. Finally, we aimed on revealing structure‐function relationships using statistical and correlation analysis.…”