Enzymatic and Microbial Electrochemistry: Approaches and Methods

Abstract

The coupling of enzymes and/or intact bacteria with electrodes has been vastly investigated due to the wide range of existing applications. These span from biomedical and biosensing to energy production purposes and bioelectrosynthesis, whether for theoretical research or pure applied industrial processes. Both enzymes and bacteria offer a potential biotechnological alternative to noble/rare metal-dependent catalytic processes. However, when developing these biohybrid electrochemical systems, it is of the utmost importance to investigate how the approaches utilized to couple biocatalysts and electrodes influence the resulting bioelectrocatalytic response. Accordingly, this tutorial review starts by recalling some basic principles and applications of bioelectrochemistry, presenting the electrode and/or biocatalyst modifications that facilitate the interaction between the biotic and abiotic components of bioelectrochemical systems. Focus is then directed toward the methods used to evaluate the effectiveness of enzyme/bacteria−electrode interaction and the insights that they provide. The basic concepts of electrochemical methods widely employed in enzymatic and microbial electrochemistry, such as amperometry and voltammetry, are initially presented to later focus on various complementary methods such as spectroelectrochemistry, fluorescence spectroscopy and microscopy, and surface analytical/characterization techniques such as quartz crystal microbalance and atomic force microscopy. The tutorial review is thus aimed at students and graduate students approaching the field of enzymatic and microbial electrochemistry, while also providing a critical and up-to-date reference for senior researchers working in the field.

Photobioelectrocatalysis of Intact Photosynthetic Bacteria Exposed to Dinitrophenol

“…The quantitative evaluation of R. capsulatus cells viability in presence of 2,4‐DNP was then performed by spectrofluorimetry by utilizing fluorescein diacetate [38] . The fluorescence spectra and the histograms presented in Figure 4 demonstrated that the long exposure to 2,4‐DNP (trace 2, R.caps ‐PDA+300.0 μM 2,4‐DNP) did not result in a complete inhibition of bacteria viability, since a clear fluorescence emission signal was observed.…”

“…The quantitative evaluation of R. capsulatus cells viability in presence of 2,4-DNP was then performed by spectrofluorimetry by utilizing fluorescein diacetate. [38] The fluorescence spectra and the histograms presented in Figure 4…”

Advanced Electroanalysis for Electrosynthesis

“…The current generated upon application of a potential provides kinetic and mechanistic information about the enzyme object of study. CV can offer insights on the type of electron transfer (ET) mechanism, direct or mediated, of both enzymes and electrogenic microbes . CV can be used to detect the presence of membrane bound redox proteins responsible for ET in electroactive bacteria and their redox potential .…”

“…The adsorption of electrochemically active molecules and the capacitive charge that is created when microbial systems are used, can indeed also contribute to the total charge consumed at the electrode . SWV, by reducing nonfaradaic contributions, allows a more accurate calculation of k ET and electroactive surface coverage …”

Application of gas diffusion electrodes in bioeconomy: An update

“…The combination of electrochemical and microbial as well as enzymatic reactions is well-established in the field of biosensors (Bedendi et al, 2022). In bioeconomy in general, this combination is believed to be highly effective to optimize established processes or to setup new production routes (Harnisch & Urban, 2018).…”