Convenient non-invasive electrochemical techniques to monitor microbial processes: current state and perspectives

Abstract

Real-time electrochemical monitoring in bioprocesses is an improvement over existing systems because it is versatile and provides more information to the user than periodic measurements of cell density or metabolic activity. Real-time electrochemical monitoring provides the ability to monitor the physiological status of actively growing cells related to electron transfer activity and potential changes in the proton gradient of the cells. Voltammetric and amperometric techniques offer opportunities to monitor electron transfer reactions when electrogenic microbes are used in microbial fuel cells or bioelectrochemical synthesis. Impedance techniques provide the ability to monitor the physiological status of a wide range of microorganisms in conventional bioprocesses. Impedance techniques involve scanning a range of frequencies to define physiological activity in terms of equivalent electrical circuits, thereby enabling the use of computer modeling to evaluate specific growth parameters. Electrochemical monitoring of microbial activity has applications throughout the biotechnology industry for generating real-time data and offers the potential for automated process controls for specific bioprocesses.Open Access This article is distributed under the terms of the Creative Comm ons Attribution 4.0 International License (http:// creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Spectral Induced Polarization (SIP) of Denitrification‐Driven Microbial Activity in Column Experiments Packed With Calcareous Aquifer Sediments

“…This is of particular value for reaction monitoring during experiments to inform the timing of geochemical sampling. In biotechnology studies, the potential of SIP as a process monitoring method is gaining increasing interest and has shown to have advantages in terms of transferability between different strains and conditions over traditional methods (Slouka et al, 2016(Slouka et al, , 2017Turick et al, 2019).…”

“…SIP has been successfully used to study nitrate reduction in sands (Mellage, Holmes, et al., 2018; Mellage et al., 2019), hydrocarbon degradation (Abdel Aal et al., 2004, 2006; Kimak et al., 2019), bacterial growth in a saline environment (Joo et al., 2021) and microbially induced precipitation of calcite (Saneiyan et al., 2019) and sulfide (Ntarlagiannis et al., 2005; Williams et al., 2005) at the laboratory scale, highlighting the potential of SIP to serve as a monitoring tool for a variety of microbially mediated processes. The method has also gained increasing interest in the live‐monitoring of bioreactors (Turick et al., 2019). Electrical impedance spectroscopy (EIS), a 2‐point measurement technique similar to SIP, is used by bioelectrochemists, where “low‐frequency EIS” refers to the same frequency range that is traditionally used in biogeophysics.…”

Ancient electrogenic survival metabolism of β -proteobacterial ammonia oxidizers for oxygen deficiency

“…These data suggest that the graphite felt electrode served as an electron acceptor for N. communis in the presence of ammonia, generating a constant anodic current at all live replicates higher than the controls. Notably, we did not observe an increase in the anodic current of live incubations, suggesting that the microbial electroactivity over this time course was insufficient to support rapid cell growth (33). N. communis may have longer doubling times while using an anaerobic energy metabolism, previously reported for Nitrosomonas europaea (6.5 days vs. 9 days in aerobic conditions; 34).…”

Advanced Electroanalysis for Electrosynthesis

“…The relative increase in current over time is directly correlated with the density of cells immobilized at the electrode as well as substrate utilization by bacteria. 172 Vice versa, when it is poised at the desired reduction potential, the electrons can be used by microbes for driving metabolic pathways involved in bioproduction. In this case, CA monitors the consumption of current by microorganisms.…”

“…172 Since EIS signals can be related to the polar nature of lipid membranes, proton gradients on the outer surface of bacterial cells, and membrane-associated ET reactions, EIS can also be employed for monitoring cell viability, density and physiology of microbial BEs. 172 The exchange current density, j ex , is a reliable parameter for evaluating the performances of BESs. BESs characterized by high j ex are able to exchange electrons and respond to a change in potential more rapidly.…”