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The development of bioelectrochemical systems requires careful selection of both their biotic and abiotic components to obtain sustainable devices. Herein, we report a biophotoelectrode obtained with polyhydroxybutyrate (PHB), a biopolymer, which purple non-sulphur bacteria produce as an energy stock under specific environmental conditions. The electrode was obtained by casting a mixture composed of PHB and carbon fibers in a 3:2 mass ratio. Following, the composite material was modified with polydopamine and thermally treated to obtain a hydrophilic electrode with improved electrochemical behavior. The bio-based electrode was tested with metabolically active cells of Rhodobacter capsulatus embedded in a biohybrid matrix of polydopamine. The system achieved enhanced catalytic activity under illumination, with an 18-fold increase in photocurrent production compared to biophotoelectrodes based on glassy carbon, reaching a current density of 12 ± 3 μ A cm−2, after 30 min of light exposure at +0.32 V. The presented biocompatible electrode provides a sustainable alternative to metal-based and critical raw material-based electrodes for bioelectrochemical systems. [ABSTRACT FROM AUTHOR]

The present work evaluates the action of nitroreductase enzyme immobilized on Tosylactivated magnetic particles (MP-Tosyl) on three disperse dyes which contain nitro and azo groups. The dyes included Disperse Red 73 (DR 73), Disperse Red 78 (DR 78), and Disperse Red 167 (DR 167). The use of a magnet enabled the rapid and easy removal of the immobilized enzyme after biotransformation; this facilitated the identification of the products generated using high-performance liquid chromatography with diode array detector (HPLC-DAD) and mass spectrometry (LC-MS/MS). The main products formed by the in vitro biotransformation were identified as the product of nitro group reduction to the correspondent amine groups, which were denoted as follows: 50% of 2-(2-(4-((2-cyanoethyl)(ethyl)amino)phenyl)hydrazinyl)-5-nitrobenzonitrile, 98% of 3-((4-((4-amino-2-chlorophenyl) diazenyl)phenyl) (ethyl)amino)propanenitrile and 99% of (3-acetamido-4 - ((4-amino-2-chlorophenyl) diazenyl) phenyl) azanediyl) bis (ethane-2,1-diyl) for DR 73, DR 78 and DR 167, respectively. Based on the docking studies, the dyes investigated were found to be biotransformed by nitroreductase enzyme due to their favorable interaction with the active site of the enzyme. Theoretical results show that DR73 dye exhibits a relatively lower rate of degradation; this is attributed to the cyanide substituent which affects the electron density of the azo group. The docking studies also indicate that all the dyes presented significant reactivity towards DNA. However, Disperse Red 73 was found to exhibit a substantially higher reactivity compared to the other dyes; this implies that the dye possesses a relatively higher mutagenic power. The docking results also show that DR 73, DR 78 and DR 167 may be harmful to both humans and the environment, since the mutagenicity of nitro compounds is associated with the products formed during the reduction of nitro groups. These products can interact with biomolecules, including DNA, causing toxic and mutagenic effects. [ABSTRACT FROM AUTHOR]

Synthetic azo dyes have increasingly become a matter of great concern as a result of the genotoxic and mutagenic potential of the products derived from azo dye biotransformation. This work evaluates the manner in which reducing enzymes produced by Escherichia coli ( E. coli ) act on three disperse dyes bearing azo groups, namely Disperse Red 73 (DR 73), Disperse Red 78 (DR 78), and Disperse Red 167 (DR 167). UV–Vis spectrophotometry, high-performance liquid chromatography with diode array detector (HPLC-DAD), and liquid chromatography mass spectrometry (LC-MS/MS) were applied towards the identification of the main products. Seven days of incubation of the azo dyes with the tested enzymes yielded a completely bleached solution. 3–4-Aminophenyl-ethyl-amino-propanitrile was detected following the biotransformation of both DR 73 and DR 78. 4-Nitroaniline and 2-chloro-4-nitroaniline were detected upon the biotransformation of DR 73 and DR 78, respectively. The main products derived from the biotransformation of DR 167 were dimethyl 3,3′-3-acetamido-4-aminophenyl-azanedyl-dipropanoate and 2-chloro-4-nitroaniline. The results imply that DR 73 lost the CN - substituent during the biotransformation. Furthermore, theoretical calculations were also carried out aiming at evaluating the interaction and reactivity of these compounds with DNA. Taken together, the results indicate that DR 73, DR 78, and DR 167 pose health risks and serious threats to both human beings and the environment at large as their biotransformation produces harmful compounds such as amines, which have been widely condemned by the International Agency for Research on Cancer. [ABSTRACT FROM AUTHOR]

We report the preparation of mono and bi-enzymatic bioanodes immobilizing dehydrogenase enzymes at the surface of a carbon support aiming to follow the 2 and 4 electron transfer of ethanol oxidation by HPLC. Enzymatic immobilization of ADH and AlDH enzymes at the bioanodes was performed using Nafion membranes modified with tetrabutylammonium salt. Themonoenzymatic film with immobilized alcohol dehydrogenase (ADH) provided, at pH 8.50, power densities of 29.5 ± 3.4 μW cm-2; however, addition of the second enzyme (AlDH) aiming to transfer 4 electrons furnished values as high as 186.0 ± 19.4 μW cm-2. These results indicate that as the product of the first oxidation is consumed by the second enzyme it inhibits the first enzyme less thus, furnishing better performance for the bienzymatic electrodes. Long-term electrolysis (12 hours) of ethanol followed by HPLC-UV/RID system confirms our electrochemical finding demonstrating formation of 2 and 4 electrons products, e.g., acetaldehyde (6.6 mmol L-1) and acetate (0.72 mmol L-1) when a two dehydrogenase enzyme system was employed. The faradaic efficiency was above 60% for the bi-enzymatic system. We demonstrate that simultaneous product identification and mass balance analysis is an important tool to follow the synergy between the enzymes within the enzymatic cascade. [ABSTRACT FROM AUTHOR]

Azo dyes are known as a group of substances with DNA damage potential that depend on the nature and number of azo groups connected to aromatic rings (benzene and naphthalene), chemical properties, e . g . solubility and reactive functional groups, which significantly affect their toxicological and ecological risks. In this paper, we used in vitro models to evaluate the metabolism of selected textile dyes: Disperse Red 73 (DR 73), Disperse Red 78 (DR 78) and Disperse Red 167 (DR 167). To evaluate the mutagenic potential of the textile dyes, the Salmonella mutagenicity assay (Ames test) with strains TA 98 and TA 100 in the presence and absence of the exogenous metabolic system (S9) was used. DR73 was considered the most mutagenic compound, inducing both replacement base pairs (TA 100) and also changing frameshift (TA 98) mutations that are reduced in the presence of the S9 mixture. Furthermore, we used rat liver microsomes in the same experimental conditions of the S9 mixture to metabolize the dyes and the resultant solutions were analyzed using a liquid chromatography coupled to a quadrupole linear ion trap mass spectrometry (LC-MS/MS) to investigate the metabolites formed by the in vitro biotransformation. Based on this experiment, we detected and identified two biotransformation products for each textile dye substrate analyzed. Furthermore, to evaluate the interaction and reactivity of these compounds with DNA, theoretical calculations were also carried out. The results showed that the chemical reaction occurred preferentially at the azo group and the nitro group, indicating that there was a reduction in these groups by the CYP P450 enzymes presented in the rat microsomal medium. Our results clearly demonstrated that the reduction of these dyes by biological systems is a great environmental concern due to increased genotoxicity for the body of living beings, especially for humans. [ABSTRACT FROM AUTHOR]

We prepared a W/WO3/TiO2 bicomposite photoanode by simple electrochemical anodization of W foil, followed by cathodic electrodeposition of TiO2 and annealing at 450°C for 30min. This photoanode shows good photoactivity under irradiation with UV and visible light. In optimized conditions, it promotes complete photoelectrocatalytic oxidation of 3.33×10−5 molL−1 basic red 51 solution (which is used in hair dye) at 0.1molL−1 Na2SO4, pH 2.0, under a current density of 1.25mAcm−2 and ultraviolet and visible radiation–total organic carbon removal is 94 and 88%, respectively. This effect paves the way for the sustainable solar-assisted remediation of water bodies contaminated with organic components of hair dyes. [ABSTRACT FROM AUTHOR]

Biofuel cells use chemical reactions and biological catalysts (enzymes or microorganisms) to produce electrical energy, providing clean and renewable energy. Enzymatic biofuel cells (EBFCs) have promising characteristics and potential applications as an alternative energy source for low-power electronic devices. Over the last decade, researchers have focused on enhancing the electrocatalytic activity of biosystems and on increasing energy generation and electronic conductivity. Self-powered biosensors can use EBFCs while eliminating the need for an external power source. This review details improvements in EBFC and catalyst arrangements that will help to achieve complete substrate oxidation and to increase the number of collected electrons. It also describes how analytical techniques can be employed to follow the intermediates between the enzymes within the enzymatic cascade. We aim to demonstrate how a high-performance self-powered sensor design based on EBFCs developed for ethanol detection can be adapted and implemented in power devices for biosensing applications. [ABSTRACT FROM AUTHOR]

The work presented herein demonstrates a hybrid bi-catalytic architecture for the complete electrochemical oxidation of ethanol. The new catalytic system contains pyrene-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidinyl-N-oxyl) immobilized on the surface of carboxylated multi-walled carbon nanotubes (MWCNT-COOH), and oxalate decarboxylase enzyme (OxDc) immobilized onto a carbon cloth electrode. Electrolysis revealed a stable amperometric curve and an excellent current density value over a duration of 10 h. In addition, the hybrid system immobilized on the carbon electrode exhibits outstanding stability after electrolysis. Nuclear magnetic resonance (NMR) and gas chromatography (GC) demonstrate that the hybrid electrode system is able to oxidize ethanol to CO 2 after 10 h of electrolysis. Overall, this study illustrates the enhancement of an enzymatic biofuel cell through the hybrid multi-catalytic systems, which exhibit high oxidation rates for all substrates involved in complete ethanol oxidation, enabling the collection of up to 12 electrons per molecule of ethanol. Image 1 • This bi-catalytic architecture system showed excellent electrocatalytic performance. • The hybrid system exhibit good stability during long term electrolysis. • The enzymatic/organic system allows for the enhancement of complete ethanol oxidation. • The multi-catalytic electrode enable collection of up to 12 electrons from ethanol. • The new system represents a promising advancement in the bioelectrochemistry. [ABSTRACT FROM AUTHOR]

We report a hybrid catalytic system containing metallic PtSn nanoparticles deposited on multiwalled carbon nanotubes (Pt 65 Sn 35 /MWCNTs), prepared by the microwave-assisted method, coupled to the enzyme oxalate oxidase (OxOx) for complete ethylene glycol (EG) electrooxidation. Pt 65 Sn 35 /MWCNTs, without OxOx, showed good electrochemical activity toward EG oxidation and all the byproducts. Pt 65 Sn 35 /MWCNTs cleaved the glyoxilic acid C-C bond, producing CO 2 and formic acid, which was further oxidized at the electrode. Concerning EG oxidation, the catalytic activity of the hybrid system (Pt 65 Sn 35 /MWCNTs+OxOx) was twice the catalytic activity of Pt 65 Sn 35 /MWCNTs. Long-term electrolysis revealed that Pt 65 Sn 35 /MWCNTs+OxOx was much more active for EG oxidation than Pt 65 Sn 35 /MWCNTs: the charge increased by 65%. The chromatographic results proved that Pt 65 Sn 35 /MWCNTs+OxOx collected all of the 10 electrons per molecule of the fuel and was able to catalyze EG oxidation to CO 2 due to the associative oxidation between the metallic nanoparticles and the enzymatic pathway. Overall, Pt 65 Sn 35 /MWCNTs+OxOx proved to be a promising system to enhance the development of enzymatic biofuel cells for further application in the bioelectrochemistry field., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Magnetic molecularly imprinted polymers (MMIPs) have become a research hotspot due to their two important characteristics: target recognition and magnetic separation. This paper presents the preparation, characterization, and optimization of an MMIP for the preconcentration of disperse red 73 dye (DR73) and its subsequent efficient degradation by photoelectrocatalytic treatment. The MMIPs were characterized by scanning electron microscopy (SEM), which revealed homogeneous distribution of the particles. Excellent encapsulation of magnetite was confirmed by transmission electron microscopy (TEM). A study of dye binding showed that the dye was retained more selectively in the MIP, compared to the NIP. The release of DR73 from the imprinted polymers into methanol and acetic acid was analyzed by UV-Vis spectrophotometry. The extracts showed higher absorbance values for MMIP, compared to MNIP, confirming greater adsorption of dye in the MMIP material. The extracts were then subjected to photoelectrocatalytic treatment. LC-MS/MS analysis following this treatment showed that the dye was almost completely degraded. Hence, the combination of MMIP extraction and photoelectrocatalysis offers an alternative way of selectively removing an organic contaminant, prior to proceeding with its complete degradation.