A review. Being inspired by a very recent review entitled: "Electrocatalysis and bioelectrocatalysis - Distinction without a difference" and following the general approach employed by Prof. Dr. Schuhmann, in the current work we point to the similarities and differences between oxygen electroredn. and bioelectroredn. processes. To addnl. distinguish our paper from the recent review we touch on different bioelements, such as redox proteins and living cells, but we still keep a special emphasis on oxidoreductases, biocatalysts par excellence. Moreover, we also exclusively focus on oxygen electroredn. based on direct electron transfer reactions. On the one hand, we corroborate the previously made conclusion regarding intrinsically high activity of the active sites of biol. catalysts, esp. redox enzymes, which results in mass transfer and heterogeneous electron transfer limited currents from oxygen reducing bioelectrodes. On the other hand, we disagree with the statements regarding the exceptionality of precious metal catalysts, and the notion of a huge trade-​off between high activity and stability of non-​precious metal catalysts and bioelements. We show that the activity and stability of noble metal based cathodes is very far from perfect, esp. when these electrodes operate in complex electrolytes, such as physiol. fluids, e.g. human blood.

Fungal high-redox-potential laccases (HRPLs) are multi-copper oxidases with a relaxed substrate specificity that is highly dependent on their binding affinity and redox potential of the T1Cu site (E-T1). In this study, we combined computational design with directed evolution to tailor an HRPL variant with increased E-T1 and activity toward high-redox-potential mediators as well as enhanced stability. Laccase mutant libraries were screened in vitro using synthetic highredox-potential mediators with different oxidation routes and chemical natures, while computer-aided evolution experiments were run in parallel to guide benchtop mutagenesis, without compromising protein stability. Through this strategy, the E-T1 of the evolved HRPL increased from 740 to 790 mV, with a concomitant improvement in thermal and acidic pH stability. The kinetic constants for high-redox-potential mediators were markedly improved and were then successfully tested within laccase systems (LMSs). Two hydrophobic substitutions surrounding the T1Cu site appeared to underlie these effects, and they were rationalized at the atomic level. Together, this study represents a proof-of-concept of the joint elevation of the E-T1, redox mediator activity, and stability in an HRPL, making this versatile biocatalyst a promising candidate for future LMS applications and for the development of bioelectrochemical devices.

Electrochemical characterization of the GreeDo variant of a high redox potential fungal laccase obtained by laboratory evolution together with computer-guided mutagenesis, in comparison to its parental variety (the OB-1 mutant), is presented. Both laccases, when immobilized on graphite electrodes either by direct physical adsorption or covalently attached via gold nanoparticles, were capable of both non-mediated and mediator-based bioelectroreduction of molecular oxygen at low overpotentials. GreeDo exhibited higher open circuit potential values and onset potentials for oxygen bioelectroreduction compared to OB-1. However, even though in homogeneous catalysis GreeDo outperforms OB-1 in terms of turnover numbers and catalytic efficiency, when exposed to high redox potential substrates, direct electron transfer based bioelectrocatalytic currents of GreeDo and OB-1 modified electrodes were similar. High operational stability of freely diffusing GreeDo and also the immobilized enzyme in the acidic electrolyte was registered, in agreement with high storage stability of GreeDo in acidic solutions.

Here we report on an entirely new kind of bioelectronic device - a conventional biosupercapacitor, which is built from copper containing redox proteins. Prior to biodevice fabrication, detailed spectroelectrochemical studies of the protein, viz. Acidithiobacillus ferrooxidcats rusticyanin, in solution and in adsorbed state, were performed, including estimation of the redox potential of the T1 site (0.62 V vs. NHE), protein midpoint potential when adsorbed on a self-assembled monolayer (0.34 V vs. NHE), as well as biocapacitance of rusticyanin modified gold electrodes (115 mu F cm(-2)). The symmetrical biosupercapacitor based on two identical gold electrodes modified with rusticyanin is able to capacitively store electricity and deliver electric power accumulated mostly in the form of biopseudocapacitance, when charged and discharged externally. When charged during Just 5 s, the biosupercapacitor with a total capacitance of about 73 mu F cm(-2) provided a maximum of 4 mu A cm(-2) peak current at 0.40 V. The biodevice, which can be charged and discharged at least 50 times without a significant loss of ability to store electric energy, had a low leakage current below 50 nA cm(-2).