industrial wastewater is also used for the treatment. The other systems such as
microbial electrolysis cell and microbial desalination cells are also developed for
the chemical production and seawater desalination, respectively. The microbes play
a very important role in these systems for electron transfer and wastewater treatment.
These microbes are much specified in the electron transfer from the anodic medium
to the anode electrode. This transfer happened either by direct transfer or use of any
mediators. The direct electron transfer has several advantages over the mediator
electron transfer, as these mediators are costly and also toxic to the environment.
Many studies shown that in the direct electron transfer the microbes make a biofilm
on the surface of the electrode and then they directly transfer these electrons to the
anode electrode. The explanation of the nitty-gritty of microbial extracellular electron transfer (EET) and its utilization in engineered systems is a fundamental and
rapidly greater than ever field of research and development (Rabaey and Rozendal
2010; Logan and Rabaey 2012; Sevda et al. 2015). The study of these electroactive
(or bioelectrocatalytic or electrochemically active) microorganisms, including pure
strains as well as defined co-cultures and complex consortia, requires a complex
arsenal of techniques, methods, and protocols (Harnisch and Rabaey 2012; Sevda
et al. 2018). These methods derive from diverse methodical disciplines,
e.g. materials science, microbiology, electrochemistry, and offer insights on different
hierarchical levels, i.e. from the complete microbial biofilm to solitary molecules.
Thereby, electrochemistry and electrochemical methods represent the fundament of
all behavior. Traditionally, fuel cell type setups were often used for the growth and
maintenance of electroactive microbial cultures in the archetype of these engineered
systems: microbial fuel cells (MFCs) (Logan et al. 2006; Sevda et al. 2016; Naha
et al. 2020). In the traditional types of MFCs often did not allow monitoring or even
scheming the potential of a single electrode and thus only limited insights in the
electrode processes were possible. Often only open cell potential is reported for the
tradition MFC. Now it is more and more approved that the monitoring and control of
the potential of single electrode in MFCs represents a clear benefit, not only for
fundamental research but also for engineering. Furthermore, with the diversification
of the applications of microbial electrochemical technologies that now include,
e.g. syntheses, remediation, desalination, and even biocomputing, in the so-called
microbial bioelectrochemical systems (BES) (Harnisch and Schröder 2010;
TerAvest et al. 2011; Sevda et al. 2018) an external control of individual electrode
potentials is often substantial. This control is usually achieved by using external
influence sources or potentiostats. The application of potentiostat in BES system
provide contol in the operating cell potential and resulting the cathodic reactions can
be used for the new product generation from CO 2 . This is of high importance as the
electrode represents the incurable microbial electron acceptor (for anodes) or electron donor (for cathodes) of the extracellular electron transfer (Lovley 2006, 2011).
Thus the control of the electrode potential enables not only the use of a reproducible microbial culturing conditions but also its tailoring in terms of EET thermodynamics (Schröder 2007; Rosenbaum et al. 2011). This includes the performance
parameters maximum current density and coulombic efficiency (CE) as well as EET
characteristics. Here the identification of the formal potentials of possible and actual
106
S. Sevda et al.
microbial electrolysis cell and microbial desalination cells are also developed for
the chemical production and seawater desalination, respectively. The microbes play
a very important role in these systems for electron transfer and wastewater treatment.
These microbes are much specified in the electron transfer from the anodic medium
to the anode electrode. This transfer happened either by direct transfer or use of any
mediators. The direct electron transfer has several advantages over the mediator
electron transfer, as these mediators are costly and also toxic to the environment.
Many studies shown that in the direct electron transfer the microbes make a biofilm
on the surface of the electrode and then they directly transfer these electrons to the
anode electrode. The explanation of the nitty-gritty of microbial extracellular electron transfer (EET) and its utilization in engineered systems is a fundamental and
rapidly greater than ever field of research and development (Rabaey and Rozendal
2010; Logan and Rabaey 2012; Sevda et al. 2015). The study of these electroactive
(or bioelectrocatalytic or electrochemically active) microorganisms, including pure
strains as well as defined co-cultures and complex consortia, requires a complex
arsenal of techniques, methods, and protocols (Harnisch and Rabaey 2012; Sevda
et al. 2018). These methods derive from diverse methodical disciplines,
e.g. materials science, microbiology, electrochemistry, and offer insights on different
hierarchical levels, i.e. from the complete microbial biofilm to solitary molecules.
Thereby, electrochemistry and electrochemical methods represent the fundament of
all behavior. Traditionally, fuel cell type setups were often used for the growth and
maintenance of electroactive microbial cultures in the archetype of these engineered
systems: microbial fuel cells (MFCs) (Logan et al. 2006; Sevda et al. 2016; Naha
et al. 2020). In the traditional types of MFCs often did not allow monitoring or even
scheming the potential of a single electrode and thus only limited insights in the
electrode processes were possible. Often only open cell potential is reported for the
tradition MFC. Now it is more and more approved that the monitoring and control of
the potential of single electrode in MFCs represents a clear benefit, not only for
fundamental research but also for engineering. Furthermore, with the diversification
of the applications of microbial electrochemical technologies that now include,
e.g. syntheses, remediation, desalination, and even biocomputing, in the so-called
microbial bioelectrochemical systems (BES) (Harnisch and Schröder 2010;
TerAvest et al. 2011; Sevda et al. 2018) an external control of individual electrode
potentials is often substantial. This control is usually achieved by using external
influence sources or potentiostats. The application of potentiostat in BES system
provide contol in the operating cell potential and resulting the cathodic reactions can
be used for the new product generation from CO 2 . This is of high importance as the
electrode represents the incurable microbial electron acceptor (for anodes) or electron donor (for cathodes) of the extracellular electron transfer (Lovley 2006, 2011).
Thus the control of the electrode potential enables not only the use of a reproducible microbial culturing conditions but also its tailoring in terms of EET thermodynamics (Schröder 2007; Rosenbaum et al. 2011). This includes the performance
parameters maximum current density and coulombic efficiency (CE) as well as EET
characteristics. Here the identification of the formal potentials of possible and actual
106
S. Sevda et al.