Waste Water Derived Electroactive Microbial Biofilms: Growth, Maintenance, and Basic Characterization

Abstract

The growth of anodic electroactive microbial biofilms from waste water inocula in a fed-batch reactor is demonstrated using a three-electrode setup controlled by a potentiostat. Thereby the use of potentiostats allows an exact adjustment of the electrode potential and ensures reproducible microbial culturing conditions. During growth the current production is monitored using chronoamperometry (CA). Based on these data the maximum current density (j max ) and the coulombic efficiency (CE) are discussed as measures for characterization of the bioelectrocatalytic performance. Cyclic voltammetry (CV), a nondestructive, i.e. noninvasive, method, is used to study the extracellular electron transfer (EET) of electroactive bacteria. CV measurements are performed on anodic biofilm electrodes in the presence of the microbial substrate, i.e. turnover conditions, and in the absence of the substrate, i.e. nonturnover conditions, using different scan rates. Subsequently, data analysis is exemplified and fundamental thermodynamic parameters of the microbial EET are derived and explained: peak potential (E p ), peak current density (j p ), formal potential (E f ) and peak separation (ΔE p ). Additionally the limits of the method and the state-of the art data analysis are addressed. Thereby this video-article shall provide a guide for the basic experimental steps and the fundamental data analysis.

A Microbial Biosensor Platform for Inline Quantification of Acetate in Anaerobic Digestion: Potential and Challenges

“…The formation of an electroactive microbial biofilm occurred within 3–6 days, being in accordance with 22, 25. After the ageing period of 14–21 days a stable performance of 0.39 ± 0.04 mA cm −2 in 10 mmol L −1 acetate solution was achieved, assuring that representative biofilm anodes were formed 22, 23, 26. Fig.…”

“…For CV, the scan rate was set to 1 mV s −1 with vertex potentials of 0.3 and −0.5 V. Three cycles were performed with only the last cycle being used for data analysis. The electroactive anodic biofilms were formed as secondary biofilms 22 within the flow cell setup but in batch mode as described in literature 23. After biofilm formation, the operational mode was changed from batch mode to flow regime and the biofilms were allowed to mature for 14–21 days, as they are subjected to ageing effects.…”

Bidirectional microbial electron transfer: Switching an acetate oxidizing biofilm to nitrate reducing conditions

“…The reactor was operated in fed-batch mode for three different fedbatch cycles in which the acetate-exhausted medium was replaced for fresh medium containing the initial amount of acetate. At all times during anodic conditions, the working electrode (WE) was polarized at +200 mV vs Ag/AgCl (+397 mV vs SHE at 25ºC) (model SP-50, Bio-logic, France) following the procedure described elsewhere (Gimkiewicz and Harnisch, 2013). Henceforth, all potentials will be referred vs SHE.…”

“…Reactor inoculation and anodic biofilm growth were carried out following the standard procedure described elsewhere (Gimkiewicz and Harnisch, 2013). Such protocol is as an effective methodology to grow an electroactive biofilm dominated by Geobacter sp.…”

Electrochemically and Bioelectrochemically Induced Ammonium Recovery

“…Reactor operation is most easily learned hands-on and confrontation with problems will allow you to operate more easily in the next run. Other aspects regarding bioelectrochemical systems are dealt with in the JoVE video article by Gimkeiwicz and Harnisch 18 .…”