Laccases are emerging as an efficient and environmentally friendly tool for developing many industrial technologies that help modify the surface properties of materials. Laccases achieve this by either directly generating reactive species on the surface of materials or by mediating the incorporation/grafting of various functional molecules on both synthetic and biobased materials. Thanks to the versatile catalytic ability of laccases, they catalyze the oxidation of a wide range of different molecules that include phenols, substituted phenols, polyphenols, aryl diamines, anilines, benzene-thiols and inorganic/organic metal compounds to generate reactive species that further none-enzymatically react among themselves or with other molecules/polymers in the surrounding milieu. Some of the laccase-oxidized low molecular weight substrates produce highly reactive species (known as laccase mediators) that either oxidize or activate other molecules which are not its substrates. The oxidized molecules can also diffuse and oxidize molecules a distance away from the enzyme itself, for example, inside polymers. Using laccase mediators, the scope of laccase substrates is widening and their application is expanding to higher-redox potential compounds than laccases themselves (in some cases bulky and recalcitrant substrates). This chapter provides a concise overview of recent progress in the development of laccase-based processes and technologies for changing the surface properties of materials.

Enzymatic polymerization of lignosulfonate (LS) has a high potential for various applications ranging from coatings to adhesives. Here, the effect of different ions in low concentrations on enzymatic polymerization of LS was investigated, including salt solutions consisting of mono- and dicarboxylic acids, sulfate, phosphate and chloride with sodium as counter ion. LS polymerization was followed by viscometry and size exclusion (SEC) chromatography. Interestingly, there was only a small effect of ions on the activity of the laccase on standard substrate ABTS, while the effect on polymerization of LS was substantially different. The presence of acetate led to a 39 % higher degree of polymerization (DP) for LS. Small angle X-ray scattering (SAXS) revealed that the structure of the enzyme was largely unaffected by the ions, while the determination of the zeta potential showed that those ions conveying higher negative surface charges onto LS particles showed lower DPs, than those not affecting the surface charge. Further, electron paramagnetic resonance (EPR) spectroscopy showed 5-times higher intensity in phenoxyl radicals for the monovalent ions compared to the divalent ones. It was concluded that the DPs of LS could be tuned in the presence of certain ions, by facilitating the interaction between the laccase substrate-binding site and the LS molecules.

The enzyme-catalyzed polymerization of lignosulfonates was investigated. Molecular formulas for the initial material (LS) and the final polymerized lignosulfonates (pLS) were determined by mass balance calculations combined with elemental analyses, allowing the elaboration of the reaction equation. Structural and chemical changes during the reaction were followed. Rheology and size exclusion chromatography showed that viscosity and molecular weight increased 90-fold and 4-fold, respectively. The thermal stability of pLS was investigated by thermogravimetric analysis and was found to be rather low compared to those of other polymers. The specific heat capacity (c(P)) was determined by differential scanning calorimetry and was higher for pLS than for LS, depending on the final formulation of the polymer. Determination of the higher heating value together with the reaction equation allowed the determination of the reaction enthalpy of -61 kJ/kg(feed). Only minor structural changes were revealed by NMR and FTIR analyses. However, these are responsible for the gained insolubility properties of pLS. Higher solubility in organic solvents of varying polarity (heptane, toluene, isopropanol, and acetone) was found for polymer films. The perturbed chain statistical associating fluid theory equation of state was found suitable to model the solution behavior of pLS films.

A reliance on fossil fuel has led to the increased emission of greenhouse gases (GHGs). The excessive consumption of raw materials today makes the search for sustainable resources more pressing than ever. Technical lignins are mainly used in low-value applications such as heat and electricity generation. Green enzyme-based modifications of technical lignin have generated a number of functional lignin-based polymers, fillers, coatings, and many other applications and materials. These bio-modified technical lignins often display similar properties in terms of their durability and elasticity as fossil-based materials while also being biodegradable. Therefore, it is possible to replace a wide range of environmentally damaging materials with lignin-based ones. By researching publications from the last 20 years focusing on the latest findings utilizing databases, a comprehensive collection on this topic was crafted. This review summarizes the recent progress made in enzymatically modifying technical lignins utilizing laccases, peroxidases, and lipases. The underlying enzymatic reaction mechanisms and processes are being elucidated and the application possibilities discussed. In addition, the environmental assessment of novel technical lignin-based products as well as the developments, opportunities, and challenges are highlighted.

Development of novel, eco-friendly coating systems for application in lawn and turf management.

Modification of kraft lignin (KL), traditionally uses harsh and energy-demanding physical and chemical processes. In this study, the potential of the bacterial laccase CotA (spore coating protein A) for oxidation of KL under mild conditions was assessed. Thereby, the efficiency of CotA to oxidize both softwood and hardwood KL of varying purity at alkaline conditions was examined. For the respective type of wood, the highest oxidation activity by CotA was determined for the medium ash content softwood KL (MA_S) and the medium ash content hardwood KL (MA_H), respectively. By an up to 95% decrease in fluorescence and up to 65% in phenol content coupling of the structural lignin units was indicated. These results correlated with an increase in viscosity and molecular weight, which increased nearly 2 and 20-fold for MA_H and about 1.3 and 6.0-fold for MA_S, respectively. Thus, this study confirms that the CotA laccase can oxidize a variety of KL at alkaline conditions, while the origin and purity of KL were found to have a major impact on the efficiency of oxidation. Under the herein tested conditions, it was observed that the MA_H KL showed the highest susceptibility to CotA oxidation when compared to the other hardwood KLs and the softwood KLs. Therefore, this could be a viable method to produce sustainable resins and adhesives.

The study investigates for the first time the possibility of using carbon rich paper recovery sludge, and nitrogen rich meat processing industry waste as cultivation medium for the production of high value enzymes needed in the respective industries. The complex cellulose rich deinking sludge was able to support the growth of many industrially relevant enzyme producing microorganisms (Bacillus licheniformis, Candida cylindracea, Aspergillus oryzae, Trichoderma reesei) and of recombinant enzyme producers (Escherichia coli and Pichia pastoris). Further detailed studies with Trichoderma reesei as model organism demonstrated that the organism was able to grow optimally in the presence of 40gL-1 paper sludge as carbon source and 67.5 gL-1 pasteurised blood as nitrogen source substituted in Mandels medium. Under these conditions cellulase activities up to 28.1 nkat FPU were achieved. Anyhow, to achieve these results pretreatment of both waste streams is inevitable. In summary, this study provides the practical basis for a valorisation systems of paper industry waste to produce valuable enzymes to be used on-site in paper processing or for other purposes. (C) 2020 The Author(s). Published by Elsevier Ltd.

The potential of lignosulfonates as widely underutilized byproducts of the pulp and paper industry for the synthesis of a biodegradable pesticide carrier system was assessed in this study. Design of experiment software MODDE Pro was for the first time applied to optimize lignosulfonate granule production using Myceliophthora thermophila laccase as a biocatalyst. Enzymatic cross-linking was monitored using size exclusion chromatography coupled online to multiangle laser light scattering, viscosity measurement, and enzyme activity. The determined optimal and experimentally confirmed incubation conditions were: 33 °C, 30 cm3/min O2 supply, and 190 min reaction time. The granules were thereafter loaded with 2 g/kg 3,6-dichloro-2-methoxybenzoic acid (Dicamba), a broad-spectrum herbicide. According to the HPLC analysis, complete release of Dicamba was achieved after 48 h of release. This study showed the green production of a 100% lignosulfonate-based biodegradable solid carrier with potential application in agriculture.

Lignin, a structural component of lignocellulosic plants, is an alternative raw material with enormous potential to replace diminishing fossil-based resources for the sustainable production of many chemicals and materials. Unfortunately, lignin's heterogeneity, low reactivity, and strong intra- and intermolecular hydrogen interactions and modifications introduced during the pulping process present significant technical challenges. However, the increasing ability to tailor lignin biosynthesis pathways by targeting enzymes and the continued discovery of more robust biocatalysts are enabling the synthesis of novel valuable products. This review summarizes how enzymes involved in lignin biosynthesis pathways and microbial enzymes are being harnessed to produce chemicals and materials and to upgrade lignin properties for the synthesis of a variety of value-added lignin industrial products.

In an attempt to reduce the loss of fertilizer due to leaching, this study investigates for the first time the possibility of synthesizing lignosulfonate-based fertilizer slow release granules by using laccases as green catalysts. Trametes hirsuta laccases (THL) extensively oxidized and polymerized lignosulfonates resulting in 62 and 54% decrease in phenolic groups from 52 g in samples incubated at pH 6 and 7, respectively, and as evidenced by the formation insoluble polymers at pH 6 and 7 in less than 2 h. Preliminary attempts to synthesize 100% lignosulfonate granules resulted in highly brittle randomly breaking particles with most particles <0.5 mm in diameter when dried. In order to produce bigger and regular sized lignosulfonate granules, 1% w/w alginate was incorporated into the polymerized lignosulfonates resulting in perfectly stable granules. Release studies showed that 100% lignosulfonate-based granules released all of the potassium nitrate and potassium phosphate in <5 days. However, in addition to helping make perfect granules, the incorporation of 1% alginate allowed the prolonged release of fertilizer over 25 days. This study therefore shows for the first time the possibility of synthesizing 100% biodegradable fertilizer delivery systems using 100% green technology "enzymes".