Lignin, the second most abundant natural polymer, is a by-product of the biorefinery and pulp and paper industries. This study was undertaken to evaluate the properties and estimate the prospects of using lignin as a by-product of the pretreatment of common reed straw (Phragmites australis) with deep eutectic solvents (DESs) of various compositions: choline chloride/oxalic acid (ChCl/OA), choline chloride/lactic acid (ChCl/LA), and choline chloride/monoethanol amine (ChCl/EA). The lignin samples, hereinafter referred to as Lig-OA, Lig-LA, and Lig-EA, were obtained as by-products after optimizing the conditions of reed straw pretreatment with DESs in order to improve the efficiency of subsequent enzymatic hydrolysis. The lignin was studied using gel penetration chromatography, UV-vis, ATR-FTIR, and 1H and 13C NMR spectroscopy; its antioxidant activity was assessed, and the UV-shielding properties of lignin/polyvinyl alcohol composite films were estimated. The DES composition had a significant impact on the structure and properties of the extracted lignin. The lignin’s ability to scavenge ABTS+• and DPPH• radicals, as well as the efficiency of UV radiation shielding, decreased as follows: Lig-OA > Lig-LA > Lig-EA. The PVA/Lig-OA and PVA/Lig-LA films with a lignin content of 4% of the weight of PVA block UV radiation in the UVA range by 96% and 87%, respectively, and completely block UV radiation in the UVB range.

Deep eutectic solvents (DESs) are an alternative to conventional organic solvents in various biocatalytic reactions. Meanwhile, there have been few studies reporting on synthetic reactions in DESs or DES-containing mixtures involving oxidoreductases. In this work, we have studied the effects of several DESs based on betaine as the acceptor of hydrogen bonds on the catalytic activity and stability of laccase from the basidial fungus Trametes hirsuta and performed enzymatic polymerization of the flavonoid dihydroquercetin (DHQ, taxifolin) in a DES–buffer mixture containing 60 vol.% of betaine-glycerol DES (molar ratio 1:2). The use of the laccase redox mediator TEMPO enabled an increased yield of DHQ oligomers (oligoDHQ), with a number average molecular weight of 1800 g mol−1 and a polydispersity index of 1.09. The structure of the synthesized product was studied using different physicochemical methods. NMR spectroscopy showed that oligoDHQ had a linear structure with an average chain length of 6 monomers. A scheme for enzymatic polymerization of DHQ in a DES–buffer mixture was also proposed.

Deep eutectic solvents (DESs) are an alternative to traditional organic solvents for enzymatic reactions between compounds with poor solubility. Biocatalytic polymerization of the flavonoid (+)-catechin (CC) was carried out with laccase from the fungus Trametes hirsuta in a DES–buffer mixture (betaine/glycerol 60 vol %–buffer 40 vol %). The conditions for the synthesis of catechin oligomers (oligoCCs) soluble in organic solvents have been selected. According to the data from high-performance liquid chromatography, the oligoCCs had average molecular weights of 10 620 and 2540 g/mol with polydispersity indices of 1.1 and 1.09, respectively. The physicochemical properties of the obtained oligomers were studied via UV-visible, FTIR, 1H and 13C NMR spectroscopy. The resulting oligoCCs inhibited the α-glucosidase activity (IC50 ~ 8 μg/mL).

Enzymatic synthesis of polyaniline (PANI) doped with bivalent copper ions was carried out on a sodium polystyrene sulfonate (PSS) template. The synthesized interpolymer complex PANI-Cu2+/PSS had an inhibitory effect on the growth of Staphylococcus aureus and Escherichia coli cells.

The oxidation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) using ammonium peroxydisulfate and the high redox potential laccase from Trametes hirsuta is studied in order to clarify the significant differences in the chemical and enzymatic polymerization reactions of aniline. As opposed to the laccase-catalyzed reaction, the chemical oxidation of TMPD proceeds in two stages. The radical cation formed at the first stage is oxidized by the peroxydisulfate ion to quinoiddiimine that can interact with the initial TMPD. The kinetics of the formation of the radical cation $${\text{TMP}}{{{\text{D}}}^{{\centerdot + }}}$$ is studied by ultraviolet–visible (UV–Vis) and electron paramagnetic resonance spectroscopy. The obtained data allow making an assumption about the difference in the mechanisms of chemical and enzymatic polymerization of aniline.

The development of novel materials with improved functional characteristics for supercapacitor electrodes is of current concern and calls for elaboration of innovative approaches. We report on an eco-friendly enzymatic synthesis of a composite based on poly(3,4-ethylenedioxythiophene) (PEDOT) and multi-walled carbon nanotubes (MWCNTs). The redox active compound, sodium 1,2-naphthoquinone-4-sulfonate (NQS), was used as a dopant for the backbone of the polymer. Oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) was catalyzed by a high redox potential laccase from the fungus Trametes hirsuta. Atmospheric oxygen served as an oxidant. A uniform thin layer of NQS-doped PEDOT formed on the surface of MWCNTs as a result of the enzymatic polymerization. The PEDOT-NQS/MWCNT composite showed a high specific capacitance of ca. 575 F g-1 at a potential scan rate of 5 mV s-1 and an excellent cycling stability within a potential window between -0.5 and 1.0 V, which makes it a promising electrode material for high-performance supercapacitors.

The copolymers of aniline (ANI) and 2-aminophenethyl alcohol (APA) were synthesized on a poly (2-acrylamido-2-methyl-1-propanesulfonic) acid (PAMPS) template with the fungal laccase Trametes hirsuta, which has a high redox potential, as the catalyst. Atmospheric oxygen was the oxidizing agent. The copolymer/PAMPS complexes were pseudo-soluble and were characterized by various physicochemical methods. The electrical conductivity of the copolymers depended on the initial molar ratio of the monomers. The copolymer synthesized at an APA : ANI ratio of 2 : 8 possessed the best characteristics. It is shown that the laccase/mediator system can be to oxidize the primary alcohol groups of the copolymer to reactive aldehyde groups.

Template polymerization of aniline was performed using a laccase-mediator system. The high redox-potential laccase from the basidiomycete fungus Trametes hirsuta was a catalyst for polymerization. The aniline dimer served as the redox mediator; atmospheric oxygen served as the oxidant. Sodium dodecylbenzenesulfonate micelles were used as a “soft” template. The biocatalytic polymerization of aniline resulted in conducting polyaniline/sodium dodecylbenzene sulfonate complex that was tested as a protective coating. The efficiency of the inhibition of copper corrosion by the complex was 86–87%, and the dissipation rate of positive and negative charges from cotton fabrics increased by 56 and 27 times, respectively.

Laccase-mediator systems (LMS) are extensively used both for degradation of various xenobiotics and synthesis of new compounds. In this work a laccase-mediator system was applied to copolymerization of aniline and 2-aminophenythyl alcohol on a 'soft' poly(2-acrylamido-2-methyl-1-propansulfonic acid) (PAMPS) template. The one-pot biocatalytic reaction resulted in obtaining a conducting copolymer/PAMPS complex with reactive aldehyde groups which enabled grafting the physiologically active compound 3,4-dihydroxy-L-phenylalanine (DOPA) to it.

Polyaniline/carboxylated multiwalled carbon-nanotube composites were synthesized with the use of laccase from the fungus Trametes hirsuta as a catalyst of aniline oxidative polymerization. Atmospheric oxygen was an oxidant. Aniline dimer adsorbed on the carbon material surface served as an enhancer of the enzymatic polymerization of aniline. The composites were synthesized in deionized water without any acidic dopant. The structure, morphology, and electrochemical characteristics of the obtained nanocomposite were examined. It has been shown that the carboxylic groups on the surface of multiwalled carbon nanotubes result in the electrochemical activity of polyaniline in solutions with a neutral pH.

The oxidative enzymatic polymerization of 3,4-ethylenedioxythiophene on a biopolymer DNA template is carried out. Laccase from fungus Trametes hirsuta with a high redox potential serves as a catalyst for the monomer polymerization; atmospheric oxygen is used as the oxidizing agent. Phosphate groups of DNA biopolymer, being dopants of the main chain of synthesized poly(3,4-ethylenedioxythiophene) (PEDOT), ensure its electrical conductivity. The physicochemical properties of the obtained complex and its morphology are studied. The conductivity of the PEDOT/DNA is ~0.15 mS/cm. The synthesized electrically conducting biocompatible PEDOT/DNA interpolymer complex can potentially be used for various biomedical purposes.

Derivatization of the natural flavonoid dihydroquercetin with p-aminobenzoic acid was carried out in an ethyl acetate/citric buffer biphasic system using laccase from the fungus Trametes hirsuta. The main reaction product yield was ~68 mol %. The product was characterized by 1H NMR, 13C NMR, and liquid chromatography-mass spectroscopy, and its structure was elucidated. The reaction product affected viability of cultured human rhabdomyosarcoma cells (RD cell line) in a dose-dependent manner and, therefore, can be of interest to pharmaceutical industry.

Multicopper oxidases such as bilirubin oxidase (BOD) from Myrothecium verrucaria and laccase (LC) from the basidial fungus Trametes hirsuta have been used as catalysts in dihydroquercetin (DHQ) oxidative polymerization. The conditions selected enabled good yields of DHQ oligomers, which were then analyzed using UV-vis, FTIR, 1Н and 13С NMR spectroscopy. DHQ oligomers synthesized using both enzymes showed higher thermostability as compared with the monomer. Depending on the oxidase, the products of DHQ polymerization differed in physicochemical properties, and as shown by NMR studies, had different structures.

A high-redox potential laccase from fungus Trametes hirsuta was used as a biocatalyst to synthesize poly(3,4-ethylenedioxythiophene) (PEDOT), which is a promising material possessing both electronic and optical properties. This enzyme only requires molecular oxygen as an oxidant, which represents a great advantage for oxidative coupling reactions. The enzymatic oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) was performed using water-soluble sodium polystyrene sulfonate (PSS) as a template. The pH of the reaction medium and Zn2+ ions influenced the rate of EDOT polymerization. The water-dispersible PEDOT/PSS complex was characterized by UV–Vis and Fourier transformed infrared spectroscopy, as well as by transmission electron microscopy. Enzymatic EDOT polymerization was also carried out in the presence of PSS and multi-walled carbon nanotubes (MWCNT). The PEDOT/PSS/MWCNT composite had a conductivity of ca. 5.7 S/cm and specific electrochemical capacitance of ca. 246 F g−1, calculated from cyclic voltammograms at a potential scan rate of 5 mV s−1.

A combination of the pseudocapacitances of both an enzymatically synthesized polyaniline/multi-walled carbon nanotube (PANI/MWCNT) composite and a gel polymer redox electrolyte was used to improve the specific characteristics of a supercapacitor.