Laccase applications in the forest products industry: A review

Diverting organic waste from landfills via insect biomanufacturing using engineered black soldier flies (Hermetia illucens)

A major roadblock towards the realisation of a circular economy are the lack of high-value products that can be generated from waste. Black soldier flies (BSF; Hermetia illucens) are gaining traction for their ability to rapidly consume large quantities of organic wastes. However, these are primarily used to produce a small variety of products, such as animal feed ingredients and fertiliser. Using synthetic biology, BSF could be developed into a novel sustainable biomanufacturing platform to valorise a broader variety of organic waste feedstocks into enhanced animal feeds, a large variety of high-value biomolecules including industrial enzymes and lipids, and improved fertiliser.

Evaluating the mechanism of soybean meal protein for boosting the laccase-catalyzed of thymol onto lignosulfonate via restraining non-specific adsorption

The control of laccase-catalyzed efficiency often relies on the utilization of modifying enzyme molecules and shielding agents. However, their elevated costs or carcinogenicity led to the inability for large-scale application. To address this concern, we found that a low-cost protein from soybean meal can reduce lignin's ineffective adsorption onto enzymes for improving the efficiency of thymol grafting to lignosulfonate. The results demonstrated that by adding 0.5 mg/mL of additional soybean meal protein, the thymol reaction ratio of the modified lignosulfonate (L-0.5 S) significantly boosted from 18.1 % to 35.0 %, with the minimal inhibitory concentrations of the L-0.5 S against Aspergillus niger dramatically improved from 12.5 mg/mL to 3.1 mg/mL. Multiple characterization methods were employed to better understand the benefit of the modification under the addition of the soybean meal protein. The CO and R1-O group content increased from 20.5 % to 37.8 % and from 65.1 % to 75.5 %, respectively. The proposed potential reaction mechanism was further substantiated by the physicochemical properties. The incorporation of soybean meal effectively mitigated the non-specific adsorption of lignosulfonate, resulting in a reduction of the surface area of lignin from 235.0 to 139.2 m2/g. The utilization of soybean meal as a cost-effective and efficient shielding agent significantly enhanced the efficiency of subsequent enzyme catalysis. Consequently, the application of soybean meal in commercial enzyme catalysis holds considerable appeal and amplifies the relevance of this study in preservative industries.

A sustainable nano-hybrid system of laccase@M-MWCNTs for multifunctional PAHs and PhACs removal from water, wastewater, and lake water

This study examined the use of modified multiwall carbon nanotubes (M-MWCNTs) with immobilized laccase (L@M-MWCNTs) for removing ciprofloxacin (Cip), carbamazepine (Cbz), diclofenac (Dcf), benzo[a]pyrene (Bap), and anthracene (Ant) from different water samples. The synthesized materials were characterized using an array of advanced analytical techniques. The physical immobilization of laccase onto M-MWCNTs was confirmed through Scanning electron microscope (SEM)-dispersive X-ray spectroscopy (EDS) analysis and Brunner-Emmet-Teller (BET) surface area measurements. The specific surface area of M-MWCNTs decreased by 65% upon laccase immobilization. There was also an increase in nitrogen content seen by EDS analysis asserting successful immobilization. The results of Boehm titration and Fourier transform infrared (FTIR) exhibited an increase in acidic functional groups after laccase immobilization. L@M-MWCNTs storage for two months maintained 77.8%, 61.6%, and 57.6% of its initial activity for 4 °C, 25 °C, and 35 °C, respectively. In contrast, the free laccase exhibited 55.3%, 37.5%, and 23.5% of its initial activity at 4 °C, 25 °C, and 35 °C, respectively. MWCNTs improved storability and widened the working temperature range of laccase. The optimum removal conditions of studied pollutants were pH 5, 25 °C, and 1.6 g/L of M-MWCNTs. These parameters led to >90% removal of the targeted pollutants for four treatment cycles of both synthetic water and spiked lake water. L@M-MWCNTs demonstrated consistent removal of >90% for up to five cycles even with spiked wastewater. The adsorption was endothermic and followed Langmuir isotherm. Oxidation, dehydrogenation, hydroxylation, and ring cleavage seem to be the dominant degradation mechanisms.

Deciphering the enzymatic grafting of vanillin onto lignosulfonate for the production of versatile aldehydes-bearing biomaterials

Modification of lignin plays a crucial role in extending its applications. While chemical functionalization has been extensively applied, exploring the enzyme-catalyzed approach for grafting phenolic molecules presents a promising avenue. Herein, we investigate the controlled laccase-mediated grafting of vanillin onto lignosulfonates (LS) as a sustainable approach to introduce aldehydes into LS, paving the way for further (bio)chemical functionalizations (e.g., reductive amination and Knoevenagel-Doebner condensations). The resulting vanillin-grafted LS is comprehensively characterized (HPLC, SEC, Pyrolysis-GC/MS, FTIR). The study reveals four key steps in the grafting process: (i) vanillin acts as a mediator, generating the phenoxyl radical that initiates LS oxidation, (ii) the oxidation leads to depolymerization of LS, resulting in a decrease in molecular weight, (iii) rearrangement in the vanillin-grafted LS, evidenced by the replacement of labile bonds by stronger 5-5 bonds that resist to pyrolysis, and (iv) if the reaction is prolonged after complete consumption of vanillin, condensation of the vanillin-grafted LS occurs, leading to a significant increase in molecular weight. This study provides valuable insights on the behavior of vanillin and LS throughout the process and allows to identify the optimal reaction conditions, thereby enhancing the production of vanillin-grafted LS for its subsequent functionalization.

Potential biodegradation of polycyclic aromatic hydrocarbons (PAHs) and petroleum hydrocarbons by indigenous fungi recovered from crude oil-contaminated soil in Iran

A total of 265 fungal individuals were isolated from soils exposed to heavy oil spills in the Yadavaran oil field in Iran to discover indigenous fungal species with a high potential to biodegrade petroleum hydrocarbon pollutants. Morphological and molecular identification of obtained fungal species led to their assignment into 16 genera and 25 species. Alternaria spp. (78%), Fusarium spp. (5%), and Cladosporium spp. (4%) were the most common genera, along with Penicillium spp., Neocamarosporium spp., Epicoccum sp., Kotlabaea sp., Aspergillus sp., Mortierella sp., and Pleurotus sp. A preliminary screening using the DCPIP indicator revealed that approximately 35% of isolates from Alternaria, Epicoccum, Neocamarosporium, Cladosporium, Fusarium, Stachybotrys, Penicillium, and Stemphylium demonstrated promising tolerance to crude oil. The best-performing isolates (12 fungal individuals) were further investigated for their capacity to mineralize a mixture of four polycyclic aromatic hydrocarbons (PAH) for 47 days, quantified by GC-MS. Eventually, two top-performing isolates, namely 5c-12 (Alternaria tenuissima) and 3b-1 (Epicoccum nigrum), were applied to petroleum-contaminated soil. The GC-MS analysis showed that 60 days after inoculation, these isolates successfully degraded more than 70% of the long-chain hydrocarbons in the soil, including C8-C16 n-alkanes, C36 n-alkane, and Pristane. This study introduces two fungal species (5c-12 and 3b-1) with high potential for biodegrading petroleum compounds and PAHs, offering promising prospects for the decontamination of oil-contaminated soil.

An insight into omics analysis and metabolic pathway engineering of lignin-degrading enzymes for enhanced lignin valorization

Lignin, a highly heterogeneous polymer of lignocellulosic biomass, is intricately associated with cellulose and hemicellulose, responsible for its strength and rigidity. Lignin decomposition is carried out through certain enzymes derived from microorganisms to promote the hydrolysis of lignin. Analyzing multi-omics data helps to emphasize the probable value of fungal-produced enzymes to degrade the lignocellulosic material, which provides them an advantage in their ecological niches. This review focuses on lignin biodegrading microorganisms and associated ligninolytic enzymes, including lignin peroxidase, manganese peroxidase, versatile peroxidase, laccase, and dye-decolorizing peroxidase. Further, enzymatic catalysis, lignin biodegradation mechanisms, vital factors responsible for lignin modification and degradation, and the design and selection of practical metabolic pathways are also discussed. Highlights were made on metabolic pathway engineering, different aspects of omics analyses, and its scope and applications to ligninase enzymes. Finally, the advantages and essential steps of successfully applying metabolic engineering and its path forward have been addressed.

Potential of the enzyme laccase for the synthesis and derivatization of antimicrobial compounds

Laccases [E.C. 1.10.3.2, benzenediol:dioxygen oxidoreductase] can oxidize phenolic substances, e.g. di- and polyphenols, hydroxylated biaryls, aminophenols or aryldiamines. This large substrate spectrum is the basis for various reaction possibilities, which include depolymerization and polymerization reactions, but also the coupling of different substance classes. To catalyze these reactions, laccases demand only atmospheric oxygen and no depletive cofactors. The utilization of mild and environmentally friendly reaction conditions such as room temperature, atmospheric pressure, and the avoidance of organic solvents makes the laccase-mediated reaction a valuable tool in green chemistry for the synthesis of biologically active compounds such as antimicrobial substances. In particular, the production of novel antibiotics becomes vital due to the evolution of antibiotic resistances amongst bacteria and fungi. Therefore, laccase-mediated homo- and heteromolecular coupling reactions result in derivatized or newly synthesized antibiotics. The coupling or derivatization of biologically active compounds or its basic structures may allow the development of novel pharmaceuticals, as well as the improvement of efficacy or tolerability of an already applied drug. Furthermore, by the laccase-mediated coupling of two different active substances a synergistic effect may be possible. However, the coupling of compounds that have no described efficacy can lead to biologically active substances by means of laccase. The review summarizes laccase-mediated reactions for the synthesis of antimicrobial compounds valuable for medical purposes. In particular, reactions with two different reaction partners were shown in detail. In addition, studies with in vitro and in vivo experimental data for the confirmation of the antibacterial and/or antifungal efficacy of the products, synthesized with laccase, were of special interest. Analyses of the structure-activity relationship confirm the great potential of the novel compounds. These substances may represent not only a value for pharmaceutical and chemical industry, but also for other industries due to a possible functionalization of surfaces such as wood or textiles.

Tailor-made alkaliphilic and thermostable fungal laccases for industrial wood processing

BACKGROUND

During the kraft process to obtain cellulosic pulp from wood, most of the lignin is removed by high-temperature alkaline cooking, released in the black liquors and usually incinerated for energy. However, kraft lignins are a valuable source of phenolic compounds that can be valorized in new bio-based products. The aim of this work is to develop laccases capable of working under the extreme conditions of high temperature and pH, typical of the industrial conversion of wood into kraft pulp and fibreboard, in order to provide extremophilic biocatalysts for depolymerising kraft lignin, and enzyme-assisted technologies for kraft pulp and fibreboard production.

RESULTS

Through systematic enzyme engineering, combining enzyme-directed evolution and rational design, we changed the optimal pH of the laccase for oxidation of lignin phenols from acidic to basic, enhanced the catalytic activity at alkaline pH and increased the thermal tolerance of the enzyme by accumulating up to eight mutations in the protein sequence. The extremophilic laccase variants show maximum activity at 70 °C and oxidize kraft lignin at pH 10. Their integration into industrial-type processes saves energy and chemicals. As a pre-bleaching stage, the enzymes promote kraft pulp bleachability and significantly reduce the need for chlorine dioxide compared to the industrial sequence. Their application in wood chips during fibreboard production, facilitates the defibering stage, with less energy required.

CONCLUSIONS

A set of new alkaliphilic and thermophilic fungal laccases has been developed to operate under the extreme conditions of high temperature and pH typical of industrial wood conversion processes. For the first time basidiomycete laccases of high-redox potential show activity on lignin-derived phenols and polymeric lignin at pH 10. Considering the extreme conditions of current industrial processes for kraft pulp and fibreboard production, the new tailor-made laccases constitute a step forward towards turning kraft pulp mills into biorefineries. Their use as biocatalysts in the wood conversion sector is expected to support the development of more environmentally sound and efficient processes, and more sustainable products.

Enzymatic Oxidation of Ca-Lignosulfonate and Kraft Lignin in Different Lignin-Laccase-Mediator-Systems and MDF Production

Laccase-mediator-oxidized lignin offers replacement for conventional chemical binders to produce fiberboards. Compared to the previously reported laccase–mediator system (LMS), a lignin-laccase-mediator-system (LLMS) has an advantage in that it requires much shorter fiber-enzyme incubation time due to significantly increased redox reactions. However, the cost of regularly applying laccase on an industrial scale is currently too high. We have employed CcLcc5 from cultures of the basidiomycete Coprinopsis cinerea as a novel basi-laccase (a CAZy subfamily AA1_1 laccase) in medium-density fiberboard (MDF) production, in comparison to the commercial formulation Novozym 51003 with recombinantly produced asco-laccase MtL (a CAZy subfamily AA1_3 laccase-like multicopper oxidase from the ascomycete Myceliophthora thermophila). With the best-performing natural mediator 2,6-dimethoxyphenol (DMP), unpurified CcLcc5 was almost as good as formulated Novozym 51003 in increasing the molecular weight (MW) of the technical lignins tested, the hydrophilic high-MW Ca-lignosulfonate and the hydrophobic low-MW kraft lignin (Indulin AT). Oxygen consumption rates of the two distantly related, poorly conserved enzymes (31% sequence identity) with different mediators and lignosulfonate were also comparable, but Indulin AT significantly reduced the oxidative activity of Novozym 51003 unlike CcLcc5, regardless of the mediator used, either DMP or guaiacol. Oxygen uptake by both laccases was much faster with both technical lignins with DMP than with guaiacol. In case of lignosulfonate and DMP, 20–30 min of incubation was sufficient for full oxygen consumption, which fits in well in time with the usual binder application steps in industrial MDF production processes. LLMS-bonded MDF was thus produced on a pilot-plant scale with either crude CcLcc5 or Novozym 51003 at reduced enzyme levels of 5 kU/kg absolutely dry wood fiber with lignosulfonate and mediator DMP. Boards produced with CcLcc5 were comparably good as those made with Novozym 51003. Boards reached nearly standard specifications in internal bond strength (IB) and modulus of rupture (MOR), while thickness swelling (TS) was less good based on the hydrophilic character of lignosulfonate. LLMS-bonded MDF with Indulin AT and DMP performed better in TS but showed reduced IB and MOR values.

Bioremediation of Industrial Pollutants by Insects Expressing a Fungal Laccase

Inadequate management of household and industrial wastes poses major challenges to human and environmental health. Advances in synthetic biology may help address these challenges by engineering biological systems to perform new functions such as biomanufacturing of high-value compounds from low-value waste streams and bioremediation of industrial pollutants. The current emphasis on microbial systems for biomanufacturing, which often requires highly preprocessed inputs and sophisticated infrastructure, is not feasible for many waste streams. Furthermore, concerns about transgene biocontainment have limited the release of engineered microbes or plants for bioremediation. Engineering of animals may provide opportunities for utilizing various waste streams that are not suitable for microbial biomanufacturing while effective transgene biocontainment options should enable in situ bioremediation. Here, we engineer the model insect Drosophila melanogaster to express a functional laccase from the fungus Trametes trogii. Laccase-expressing flies reduced concentrations of the endocrine disruptor bisphenol A by more than 50% when present in their growth media. A lyophilized powder prepared from engineered adult flies retained substantial enzymatic activity, degrading more than 90% of bisphenol A and the textile dye indigo carmine in aqueous solutions. Our results demonstrate that transgenic animals may be used to bioremediate environmental contaminants in vivo and serve as novel production platforms for industrial enzymes. These results support further development of insects, and possibly other animals, as bioproduction platforms and their potential use in bioremediation.

Bioactive Properties of a Novel Antibacterial Dye Obtained from Laccase-Mediated Oxidation of 8-Anilino-1-naphthalenesulfonic Acid

Fungal laccase obtained from a Cerrena unicolor strain was used as an effective biocatalyst for the transformation of 8-anilino-1-naphthalenesulfonic acid into a green-coloured antibacterial compound, which can be considered as both an antimicrobial agent and a textile dye, simultaneously. The process of biosynthesis was performed in buffered solutions containing methanol as a co-solvent, allowing better solubilisation of substrate. The transformation process was optimised in terms of the buffer pH value, laccase activity, and concentrations of the substrate and co-solvent. The crude product obtained exhibited low cytotoxicity, antibacterial properties against Staphylococcus aureus and Staphylococcus epidermidis, and antioxidant properties. Moreover, the synthesised green-coloured compound proved non-allergenic and demonstrated a high efficiency of dyeing wool fibres.

Enzymatic Conversion of Lignosulfonate into Wood Adhesives: A Next Step towards Fully Biobased Composite Materials

This study investigates the effect of the enzymatic polymerization of lignosulfonate for the formulation of a lignosulfonate-based adhesive. For this, beech lamellas were glued together and tested according to the EN 302-1 standard. The results showed that the laccase-polymerized lignosulfonate-based wood adhesives (LS-p) had similar mechanical properties as a standard carpenter’s glue (PVAc-based D3 class white glue), as no significant difference in tensile shear strength between these two adhesive types was found. However, carpenter’s glue showed almost 100% wood failure, while with the lignosulfonate-based wood glue, the samples failed, mainly in the glueline. Pre-polymerization of LS-p is the most critical factor to achieve the required viscosity, which is also connected to the wetting properties and the resulting tensile shear strength. The longer the pre-polymerization, the higher the viscosity of the LS-p adhesive, with the tensile shear strength reaching a plateau. The presented data show the potential of using enzymatically pre-polymerized lignosulfonate as a well-performing wood adhesive. Further development and optimization of the pre-polymerization process is required, which is also important to push towards upscaling and practical applications.

Lignocellulose degradation for the bioeconomy: The potential of enzyme synergies between xylanases, ferulic acid esterase and laccase for the production of arabinoxylo-oligosaccharides

The success of establishing bioeconomies replacing current economies based on fossil resources largely depends on our ability to degrade recalcitrant lignocellulosic biomass. This study explores the potential of employing various enzymes acting synergistically on previously pretreated agricultural side streams (corn bran, oat hull, soluble and insoluble oat bran). Degrees of synergy (oligosaccharide yield obtained with the enzyme combination divided by the sum of yields obtained with individual enzymes) of up to 88 were obtained. Combinations of a ferulic acid esterase and xylanases resulted in synergy on all substrates, while a laccase and xylanases only acted synergistically on the more recalcitrant substrates. Synergy between different xylanases (glycoside hydrolase (GH) families 5 and 11) was observed particularly on oat hulls, producing a yield of 57%. The synergistic ability of the enzymes was found to be partly due to the increased enzyme stability when in combination with the substrates.

Laccase as a Tool in Building Advanced Lignin-Based Materials

Lignin is an abundant natural feedstock that offers great potential as a renewable substitute for fossil-based resources. Its polyaromatic structure and unique properties have attracted significant research efforts. The advantages of an enzymatic over chemical or thermal approach to construct or deconstruct lignins are that it operates in mild conditions, requires less energy, and usually uses non-toxic chemicals. Laccase is a widely investigated oxidative enzyme that can catalyze the polymerization and depolymerization of lignin. Its dual nature causes a challenge in controlling the overall direction of lignin-laccase catalysis. In this Review, the factors that affect laccase-catalyzed lignin polymerization were summarized, evaluated, and compared to identify key features that favor lignin polymerization. In addition, a critical assessment of the conditions that enable production of novel lignin hybrids via laccase-catalyzed grafting was presented. To assess the industrial relevance of laccase-assisted lignin valorization, patented applications were surveyed and industrial challenges and opportunities were analyzed. Finally, our perspective in realizing the full potential of laccase in building lignin-based materials for advanced applications was deduced from analysis of the limitations governing laccase-assisted lignin polymerization and grafting.

Recent advances in carbon nanotubes-based biocatalysts and their applications

Enzymes have been incorporated into a wide variety of fields and industries as they catalyze many biochemical and chemical reactions. The immobilization of enzymes on carbon nanotubes (CNTs) for generating nano biocatalysts with high stability and reusability is gaining great attention among researchers. Functionalized CNTs act as excellent support for effective enzyme immobilization. Depending on the application, the enzymes can be tailored using the various surface functionalization techniques on the CNTs to extricate the desirable characteristics. Aiming at the preparation of efficient, stable, and recyclable nanobiocatalysts, this review provides an overview of the methods developed to immobilize the various enzymes. Various applications of carbon nanotube-based biocatalysts in water purification, bioremediation, biosensors, and biofuel cells have been comprehensively reviewed.

Enhancement of Wood Biological Resistance and Fire Retardant Properties after Laccase Assisted Enzymatic Grafting

Several treatments of wood, based on laccase assisted grafting, were evaluated in this paper. Firstly, the efficacy of lignosulfonate and kraft lignin from Eucalyptus spp. as a wood preservative was assessed. Both ligno products were anchored to wood surfaces via laccase treatment in order to avoid leaching. Moreover, some of these wood preservative treatments were completed with the addition of silver nanoparticles. For comparison, a commercial product was also analyzed in terms of its fungal decay resistance during surface application, in accordance to use class 3, CEN EN 335. Secondly, the anchoring of a flame retardant based on tetrabromobisphenol-A (TBBPA) was attempted, to limit the dispersion of this toxic substance from treated wood. In both cases, kraft lignin and lignosulfonate showed an improvement in wood durability, even after leaching. However, the addition of silver nanoparticles did not improve the efficacy. On the other hand, the efficacy of TBBPA as a flame retardant was not improved by grafting it with laccase treatment or by adding O2, a co-factor of laccase.

Extremophilic Oxidoreductases for the Industry: Five Successful Examples With Promising Projections

In a global context where the development of more environmentally conscious technologies is an urgent need, the demand for enzymes for industrial processes is on the rise. Compared to conventional chemical catalysts, the implementation of biocatalysis presents important benefits including higher selectivity, increased sustainability, reduction in operating costs and low toxicity, which translate into cleaner production processes, lower environmental impact as well as increasing the safety of the operating staff. Most of the currently available commercial enzymes are of mesophilic origin, displaying optimal activity in narrow ranges of conditions, which limits their actual application under industrial settings. For this reason, enzymes from extremophilic microorganisms stand out for their specific characteristics, showing higher stability, activity and robustness than their mesophilic counterparts. Their unique structural adaptations allow them to resist denaturation at high temperatures and salinity, remain active at low temperatures, function at extremely acidic or alkaline pHs and high pressure, and participate in reactions in organic solvents and unconventional media. Because of the increased interest to replace chemical catalysts, the global enzymes market is continuously growing, with hydrolases being the most prominent type of enzymes, holding approximately two-third share, followed by oxidoreductases. The latter enzymes catalyze electron transfer reactions and are one of the most abundant classes of enzymes within cells. They hold a significant industrial potential, especially those from extremophiles, as their applications are multifold. In this article we aim to review the properties and potential applications of five different types of extremophilic oxidoreductases: laccases, hydrogenases, glutamate dehydrogenases (GDHs), catalases and superoxide dismutases (SODs). This selection is based on the extensive experience of our research group working with these particular enzymes, from the discovery up to the development of commercial products available for the research market.

Chemical and biochemical bleaching of oat hulls: The effect of hydrogen peroxide, laccase, xylanase and sonication on optical properties and chemical composition

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Alkaline hydrogen peroxide is a mild and robust bleaching method for oat hulls.

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The lignocellulose content is not altered during alkaline H₂O₂ bleaching.

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Neither phenolic acids nor coniferaldehyde structures are removed during bleaching.

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Laccase, xylanase and sonication are not suitable for biobleaching of oat hulls.

Oat hulls are an excellent dietary fibre source for food supplements due to their rich lignocellulose composition as well as their great abundance as low-value agricultural side stream. For the production of white fibre supplements, a mild, but effective bleaching of the hulls is required. Chemical bleaching with hydrogen peroxide and sodium hydroxide was here found to be a suitable method increasing the CIE L* value (corresponds to a lightness value) above 85. The developed method is mild, retaining the hull’s chemical composition. Only a minor decrease in coniferaldehyde structures upon bleaching was detected. Colour and chemical variabilities of oat hulls from different growth seasons did not influence the required bleaching conditions to achieve the desired optical properties. The inclusion of biochemical bleaching steps utilizing the xylanase Pentopan Mono BG, the laccase NS51003 and sonication was industrially not feasible as they could not reduce the required amount of subsequently applied bleaching chemicals significantly.

The optimization of enzymatic oxidation of levofloxacin, a fluoroquinolone antibiotic for wastetwater treatment

The global presence of antibiotics in the environment has created concerns about the emergence of antibiotic resistance bacteria and potential hazard to humans and the ecosystem. This work aims to study the removal of levofloxacin, a new generation fluoroquinolone antibiotic from aqueous solutions by enzyme mediated oxidation process and optimization of the conditions thereof by response surface methodology (RSM) using Box-Behnken design (BBD). For this study, experiments were conducted to analyze the effect of independent variables namely, pH, temperature, mediator concentration and antibiotic concentration on the degradation percentage of levofloxacin antibiotic using laccase enzyme derived from Trametes versicolor. The residual levofloxacin concentration was determined using high performance liquid chromatography (HPLC). On applying the quadratic regression analysis, among the main parameters, it was found that the percentage degradation was significantly affected by all the four variables. The predicted values for percentage degradation of levofloxacin were close to the experimental values obtained and the R² (0.95) indicated that the regression was able to give a good prediction of response for the percentage degradation of levofloxacin in the studied range. The optimal conditions for the maximum degradation (99.9%) as predicted by the BBD were: temperature of 37 °C, pH of 4.5, mediator concentration of 0.1 mM and levofloxacin concentration of 5 μg mL^-1. The findings of the study were further extended to study the effect of partially purified enzymes isolated from Pleurotus eryngii, Pleurotus florida and Pleurotus sajor caju on the degradation of levofloxacin at concentrations ranging from as low as 0.1 to as high as 50 µg mL^-1 in synthetic wastewater utilizing the optimized conditions generated by BBD. A maximum degradation of 88.8% was achieved with the partially purified enzyme isolated from Pleurotus eryngii at 1 µg mL^-1 levofloxacin concentration which was at par with the commercial laccase which showed 89% degradation in synthetic wastewater at the optimized conditions. The biodegradation studies were conducted using only 2 units of laccase. Thus, the expensive commercial laccase can be effectively replaced by crude laccase isolated from indigenous macrofungi such as P. eryngii, P. florida and P. sajor caju as a cost effective alternative to degrade levofloxacin present in contaminated wastewater using as low as 2 units of enzyme for a 72 h treatment period.

Mechanism of Laccase Induction via Emodin in Trametes versicolor

Secondary metabolites of traditional Chinese herbs can prominently stimulate the production of laccase from white rot fungi during submerged fermentation. However, the molecular mechanism through which these natural products induce the production of laccase remains unknown. In this study, the Chinese herbal medicine Polygonum cuspidatum was used to induce laccase production in Trametes versicolor, and the best inducer was identified in emodin, even under conditions of 1000-L, large-scale fermentation. Proteomics analysis identified a selection of proteins that were differentially expressed in the presence of emodin, indicating that emodin may affect the expression of laccase genes through three mechanisms: reducing bioenergy productivity, the aryl hydrocarbon receptor (AHR)/xenobiotic response element (XRE) pathway, and the nuclear erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway. Combined with protoplast flow cytometry and fluorescence, it is revealed that emodin might reduce the synthesis of ATP by lowering the mitochondrial membrane potential, leading to the subsequent responses.

Optimization of protease production from Bacillus halodurans under solid state fermentation using agrowastes

Marine microbes are potential source for novel metabolites. They are efficient in producing these metabolites utilizing agrowastes. Protease is one of the enzymes which find wide industrial applications. In the present study, protease producing bacteria was isolated from marine sediments and the organism was identified as Bacillus halodurans. The organism was subjected to protease production under solid state fermentation (SSF) using different agrowastes as substrates. Among the substrates used, wheat bran yielded maximum quantity of protease. The fermentation process was carried out under different cultural conditions to optimize the parameters influencing the enzyme production. The results of the stain removal studies by the enzyme revealed the increased efficiency of the microbial enzyme than the commercial detergent.

Advances in laccase-triggered anabolism for biotechnology applications

This is the first comprehensive overview of laccase-triggered anabolism from fundamental theory to biotechnology applications. Laccase is a typical biological oxidordeuctase that induces the one-electronic transfer of diverse substrates for engendering four phenoxy radicals with concomitant reduction of O₂ into 2H₂O. In vivo, laccase can participate in anabolic processes to create multifarious functional biopolymers such as fungal pigments, plant lignins, and insect cuticles, using mono/polyphenols and their derivatives as enzymatic substrates, and is thus conducive to biological tissue morphogenesis and global carbon storage. Exhilaratingly, fungal laccase has high redox potential (E° = 500-800 mV) and thermodynamic efficiency, making it a remarkable candidate for utilization as a versatile catalyst in the green and circular economy. This review elaborates the anabolic mechanisms of laccase in initiating the polymerization of natural phenolic compounds and their derivatives in vivo via radical-based self/cross-coupling. Information is also presented on laccase immobilization engineering that expands the practical application ranges of laccase in biotechnology by improving the enzymatic catalytic activity, stability, and reuse rate. Particularly, advances in biotechnology applications in vitro through fungal laccase-triggered macromolecular biosynthesis may provide a key research direction beneficial to the rational design of green chemistry.

Bacterial valorization of pulp and paper industry process streams and waste

The pulp and paper industry is a major source of lignocellulose-containing streams. The components of lignocellulose material are lignin, hemicellulose, and cellulose that may be hydrolyzed into their smaller components and used as feedstocks for valorization efforts. Much of this material is contained in underutilized streams and waste products, such as black liquor, pulp and paper sludge, and wastewater. Bacterial fermentation strategies have suitable potential to upgrade lignocellulosic biomass contained in these streams to value-added chemicals. Bacterial conversion allows for a sustainable and economically feasible approach to valorizing these streams, which can bolster and expand applications of the pulp and paper industry. This review discusses the composition of pulp and paper streams, bacterial isolates from process streams that can be used for lignocellulose biotransformations, and technological approaches for improving valorization efforts. KEY POINTS: • Reviews the conversion of pulp and paper industry waste by bacterial isolates. • Metabolic pathways for the breakdown of lignocellulose components. • Methods for isolating bacteria, determining value-added products, and increasing product yields.

Recent environmental applications of and development prospects for immobilized laccase: a review

Laccases have enormous potential as promising 'green' biocatalysts in environmental applications including wastewater treatment and polluted soil bioremediation. The catalytic oxidation reaction they perform uses only molecular oxygen without other cofactors, and the only product after the reaction is water. The immobilization of laccase offers several improvements such as protected activity and enhanced stability over free laccase. In addition, the reusability of immobilized laccase is adistinct advantage for future applications. This review covers the sources of and progress in laccase research, and discusses the different methodologies of laccase immobilization that have emerged in the recent 5-10 years, as well as its applications to environmental fields, and evaluates these emerging technologies. Abbreviations: (2,4,6-TCP): 2,4,6-trichlorophenol; (2,4-DCP): 2,4-dichlorophenol; (ABTS), 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid); (ACE), acetaminophen; (BC-AS), almond shell; (BC-PM), pig manure; (BC-PW), pine wood; (BPA), bisphenol A; (BPA), bisphenol A; (BPF), bisphenol F; (BPS), bisphenol S; (C₆₀), fullerene; (Ca-AIL), calcium-alginate immobilized laccase; (CBZ), carbamazepine; (CETY), cetirizine; (CHT-PGMA-PEI-Cu (II) NPs), Cu (II)-chelated chitosan nanoparticles; (CLEAs), cross-linked enzyme aggregates; (CMMC), carbon-based mesoporous magnetic composites; (COD), chemical oxygen demand; (CPH), ciprofloxacin hydrochloride; (CS), chitosan; (CTC), chlortetracycline; (Cu-AIL), copper-alginate immobilized laccase; (DBR K-4BL), Drimarene brilliant red K-4BL; (DCF), diclofenac; (E1),estrone; (E2), 17 β-estradiol; (EDC), 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride; (EDCs), endocrine disrupting chemicals; (EE2), 17α-ethinylestradiol; (EFMs), electrospun fibrous membranes; (FL), free laccase; (fsMP), fumed silica microparticles; (GA-CBs), GLU-crosslinked chitosan beads; (GA-CBs), glutaraldehyde-crosslinked chitosan beads; (GA-Zr-MOF), graphene aerogel-zirconium-metal organic framework; (GLU), glutaraldehyde; (GO), graphene oxide; (HMCs), hollow mesoporous carbon spheres; (HPEI/PES), hyperbranched polyethyleneimine/polyether sulfone; (IC), indigo carmine; (IL), immobilized laccase; (k_cat), catalytic constant; (K_m), Michealis constant; (M-CLEAs), Magnetic cross-linked enzyme aggregates; (MMSNPs-CPTS-IDA-Cu²⁺), Cu²⁺-chelated magnetic mesoporous silica nanoparticles; (MSS), magnetic mesoporous silica spheres; (MWNTs), multi-walled carbon nanotubes; (MWNTs), multi-walled carbon nanotubes; (NHS), N-hydroxy succinimide; (O-MWNTs), oxidized-MWNTs; (P(AAm-NIPA)), poly(acrylamide-N-isopropylacrylamide); (p(GMA)), poly(glycidyl methacrylate); (p(HEMA)), poly(hydroxyethyl methacrylate); (p(HEMA-g-GMA)-NH₂, poly(glycidyl methacrylate) brush grafted poly(hydroxyethyl methacrylate); (PA6/CHIT), polyamide 6/chitosan; (PAC), powdered active carbon; (PAHs), polycyclic aromatic hydrocarbons; (PAM-CTS), chitosan grafted polyacrylamide hydrogel; (PAN/MMT/GO), polyacrylonitrile/montmorillonite/graphene oxide; (PAN/PVdF), polyacrylonitrile/polyvinylidene fluoride; (PEG), poly ethylene glycol; (PEI), Poly(ethyleneimine); (poly(4-VP)), poly(4-vinyl pyridine); (poly(GMA-MAA)), poly(glycidyl methacrylate-methacrylic acid); (PVA), polyvinyl alcohol; (RBBR), Remazol Brilliant Blue R; (SDE), simulated dye effluent; (semi-IPNs), semi-interpenetrating polymer networks; (TC), tetracycline; (TCH), tetracycline hydrochloride; (TCS), triclosan; (Vmax), maximum activity; (Zr-MOF, MMU), micro-mesoporous Zr-metal organic framework.

A novel and highly active recombinant spore-coat bacterial laccase, able to rapidly biodecolorize azo, triarylmethane and anthraquinonic dyestuffs

Laccases are enzymes able to catalyze the oxidation of a wide array of phenolic and non-phenolic compounds using oxygen as co-substrate and releasing water as by-product. They are well known to have wide substrate specificity and in recent years, have gained great biotechnological importance. To date, most well studied laccases are from fungal and mesophilic origin, however, enzymes from extremophiles possess an even greater potential to withstand the extreme conditions present in many industrial processes. This research work presents the heterologous production and characterization of a novel laccase from a thermoalkaliphilic bacterium isolated from a hot spring in a geothermal site. This recombinant enzyme exhibits remarkably high specific activity (>450,000 U/mg) at 70 °C, pH 6.0, using syringaldazine substrate, it is active in a wide range of temperature (20-90 °C) and maintains over 60% of its activity after 2 h at 60 °C. Furthermore, this novel spore-coat laccase is able to biodecolorize eight structurally different recalcitrant synthetic dyes (Congo red, methyl orange, methyl red, Coomassie brilliant blue R250, bromophenol blue, malachite green, crystal violet and Remazol brilliant blue R), in just 30 min at 40 °C in the presence of the natural redox mediator acetosyringone.

Halophilic archaea and their potential to generate renewable fuels and chemicals

Lignocellulosic biofuels and chemicals have great potential to reduce our dependence on fossil fuels and mitigate air pollution by cutting down on greenhouse gas emissions. Chemical, thermal, and enzymatic processes are used to release the sugars from the lignocellulosic biomass for conversion to biofuels. These processes often operate at extreme pH conditions, high salt concentrations, and/or high temperature. These harsh treatments add to the cost of the biofuels, as most known biocatalysts do not operate under these conditions. To increase the economic feasibility of biofuel production, microorganisms that thrive in extreme conditions are considered as ideal resources to generate biofuels and value-added products. Halophilic archaea (haloarchaea) are isolated from hypersaline ecosystems with high salt concentrations approaching saturation (1.5-5 M salt concentration) including environments with extremes in pH and/or temperature. The unique traits of haloarchaea and their enzymes that enable them to sustain catalytic activity in these environments make them attractive resources for use in bioconversion processes that must occur across a wide range of industrial conditions. Biocatalysts (enzymes) derived from haloarchaea occupy a unique niche in organic solvent, salt-based, and detergent industries. This review focuses on the use of haloarchaea and their enzymes to develop and improve biofuel production. The review also highlights how haloarchaea produce value-added products, such as antibiotics, carotenoids, and bioplastic precursors, and can do so using feedstocks considered "too salty" for most microbial processes including wastes from the olive-mill, shell fish, and biodiesel industries.

Lignin-Based Pesticide Delivery System

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.

Ligninolytic enzymes and its mechanisms for degradation of lignocellulosic waste in environment

Ligninolytic enzymes play a key role in degradation and detoxification of lignocellulosic waste in environment. The major ligninolytic enzymes are laccase, lignin peroxidase, manganese peroxidase, and versatile peroxidase. The activities of these enzymes are enhanced by various mediators as well as some other enzymes (feruloyl esterase, aryl-alcohol oxidase, quinone reductases, lipases, catechol 2, 3-dioxygenase) to facilitate the process for degradation and detoxification of lignocellulosic waste in environment. The structurally laccase is isoenzymes with monomeric or dimeric and glycosylation levels (10–45%). This contains four copper ions of three different types. The enzyme catalyzes the overall reaction: 4 benzenediol + O₂ to 4 benzosemiquinone + 2H₂O. While, lignin peroxidase is a glycoprotein molecular mass of 38–46 kDa containing one mole of iron protoporphyrin IX per one mol of protein, catalyzes the H₂O₂ dependent oxidative depolymerization of lignin. The manganese peroxidase is a glycosylated heme protein with molecular mass of 40–50kDa. It depolymerizes the lignin molecule in the presence of manganese ion. The versatile peroxidase has broad range substrate sharing typical features of the manganese and lignin peroxidase families. Although ligninolytic enzymes have broad range of industrial application specially the degradation and detoxification of lignocellulosic waste discharged from various industrial activities, its large scale application is still limited due to lack of limited production. Further, the extremophilic properties of ligninolytic enzymes indicated their broad prospects in varied environmental conditions. Therefore it needs more extensive research for understanding its structure and mechanisms for broad range commercial applications.

Thermophiles and the applications of their enzymes as new biocatalysts

Ecological and efficient alternatives to industrial processes have sparked interest for using microorganisms and enzymes as biocatalysts. One of the difficulties is finding candidates capable of resisting the harsh conditions in which industrial processes usually take place. Extremophiles, microorganisms naturally found in "extreme" ecological niches, produce robust enzymes for bioprocesses and product development. Thermophiles like Geobacillus, Alyciclobacillus, Anoxybacillus, Pyrococcus and Thermoccocus are some of the extremophiles containing enzymes showing special promise for biocatalysis. Glutamate dehydrogenase used in food processes, laccases and xylanases in pulp and paper processes, nitrilases and transaminases for pharmaceutical drug synthesis and lipases present in detergents, are examples of the increasing use of enzymes for biocatalytic synthesis from thermophilic microorganisms. Some of these enzymes from thermophiles have been expressed as recombinant enzymes and are already in the market. Here we will review recent discoveries of thermophilic enzymes and their current and potential applications in industry.

Optimization of Laccase/Mediator System (LMS) Stage Applied in Fractionation of Eucalyptus globulus

In a biorefinery framework, a laccase/mediator system treatment following autohydrolysis was carried out for eucalyptus wood prior to soda-anthraquinone pulping. The enzymatic and autohydrolysis conditions, with a view to maximizing the extraction of hemicelluloses while preserving the integrity of glucan, were optimized. Secondly, pulping of solid phase from Eucalyptus globulus wood autohydrolysis and the enzymatic process was carried out and compared with a conventional soda-anthraquinone (AQ) pulping process. The prehydrolysis and enzymatic delignification of the raw material prior to the delignification with soda- Anthraquinone (AQ) results in paper sheets with a lower kappa number and brightness and strength properties close to conventional soda-AQ paper and a liquid fraction rich in hemicellulose compounds that can be used in additional ways. The advantage of this biorefinery scheme is that it requires a lower concentration of chemical reagents, and lower operating times and temperature in the alkaline delignification stage, which represents an economic and environmental improvement over the conventional process.

Green potential of Pleurotus spp. in biotechnology

BACKGROUND

The genus Pleurotus is most exploitable xylotrophic fungi, with valuable biotechnological, medical, and nutritional properties. The relevant features of the representatives of this genus to provide attractive low-cost industrial tools have been reported in numerous studies to resolve the pressure of ecological issues. Additionally, a number of Pleurotus species are highly adaptive, do not require any special conditions for growth, and possess specific resistance to contaminating diseases and pests. The unique properties of Pleurotus species widely used in many environmental technologies, such as organic solid waste recycling, chemical pollutant degradation, and bioethanol production.

METHODOLOGY

The literature study encompasses peer-reviewed journals identified by systematic searches of electronic databases such as Google Scholar, NCBI, Springer, ResearchGate, ScienceDirect, and ISI Web of Knowledge. The search scheme was divided into several steps, as described below.

RESULTS

In this review, we describe studies examining the biotechnological feasibility of Pleurotus spp. to elucidate the importance of this genus for use in green technology. Here, we review areas of application of the genus Pleurotus as a prospective biotechnological tool.

CONCLUSION

The incomplete description of some fungal biochemical pathways emphasises the future research goals for this fungal culture.

Decolorization and detoxification of textile wastewaters by recombinant Myceliophthora thermophila and Trametes trogii laccases

Laccases are multi-copper oxidoreductases with broad biotechnological applications. Here, we report detailed biochemical characterization of purified recombinant laccases originating from Myceliophthora thermophila (MtL) and Trametes trogii (TtL). We identified optimal conditions for decolorization of commercial dyes and textile wastewater samples. We also tested the toxicity of decolorized wastewater samples using human peripheral blood mononuclear cells. MtL and TtL were expressed in Saccharomyces cerevisiae, and secreted enzymes were purified by consecutive hydrophobic and gel chromatography. The molecular masses of TtL (~ 65 kDa) and MtL (> 100 kDa) suggested glycosylation of the recombinant enzymes. Deglycosylation of MtL and TtL led to 25% and 10% decreases in activity, respectively. In a thermal stability assay, TtL retained 61% and MtL 86% of the initial activity at 40 °C. While TtL retained roughly 50% activity at 60 °C, MtL lost stability at temperatures higher than 40 °C. MtL and TtL preferred syringaldazine as a substrate, and the catalytic efficiencies for ABTS oxidation were 7.5 times lower than for syringaldazine oxidation. In the presence of the mediator HBT, purified TtL almost completely decolorized dyes within 30 min and substantially decolorized wastewater samples from a textile factory (up to 74%) within 20 h. However, products of TtL-catalyzed decolorization were more toxic than MtL-decolorized products, which were almost completely detoxified.

Multiple Reaction Monitoring for quantitative laccase kinetics by LC-MS

Laccases (EC 1.10.3.2) are enzymes known for their ability to catalyse the oxidation of phenolic compounds using molecular oxygen as the final electron acceptor. Lignin is a natural phenylpropanoids biopolymer whose degradation in nature is thought to be aided by enzymatic oxidation by laccases. Laccase activity is often measured spectrophotometrically on compounds such as syringaldazine and ABTS which poorly relate to lignin. We employed natural phenolic hydroxycinnamates having different degree of methoxylations, p-coumaric, ferulic and sinapic acid, and a lignin model OH-dilignol compound as substrates to assess enzyme kinetics by HPLC-MS on two fungal laccases Trametes versicolor laccase, Tv and Ganoderma lucidum laccase, Gl. The method allowed accurate kinetic measurements and detailed insight into the product profiles of both laccases. Both Tv and Gl laccase are active on the hydroxycinnammates and show a preference for substrate with methoxylations. Product profiles were dominated by the presence of dimeric and trimeric species already after 10 minutes of reaction and similar profiles were obtained with the two laccases. This new HPLC-MS method is highly suitable and accurate as a new method for assaying laccase activity on genuine phenolic substrates, as well as a tool for examining laccase oxidation product profiles.

The Influence of Adhesive Compounds Biochemical Modification on the Mechanical Properties of Adhesive Joints

The main purpose of this paper was to determine the effect of biochemical modification of epoxy adhesive compounds on the mechanical properties of hot-dip galvanized steel sheet DX51+Z275 adhesive joints. The epoxy adhesives (resin and curing agent) were biochemically modified by lyophilized fungal metabolites (in the form of lyophilized fungal fractions or materials preparation containing low molecular weight secondary metabolites of lignocellulose-degrading white rot fungi (WRF) Pycnoporus sanguineus (L.) Murrill and prepared by two methods). The epoxy adhesives (epoxy resin Epidian 53 and poliaminoamide curing agent PAC) were biochemical modified by lyophilized fungal metabolites and prepared by two methods. In the first method (Method I), the epoxy resin and the curing agent were mixed with the fungal material in the desired concentration. In the second method (Method II), the resin was mixed with mortar-grounded lyophilized post-culture liquid of the desired concentration and after following thorough mixing, a suitable amount of the poliaminoamide curing agent was added. The single-lap adhesive joints were prepared by modified epoxy adhesive compounds and were cured in various climatic factors. The specimens of adhesive joints were cured at single stage at the same temperature and humidity as during adhesive bonding (Variant A and Variant B). At the second stage, Method I adhesive joints were seasoned for two months at the temperature of 50 °C and 50% humidity in a climate test chamber (Variant C). The shear strength tests of the single-lap adhesive joints were performed using a Zwick/Roell Z150 testing machine in accordance with the DIN EN 1465 standard. The analysis of results revealed that the addition of the biological modifier can lead to reduced adhesive joint strength in ambient conditions, yet at elevated temperature and the higher humidity it results in a significant increase in adhesive joint strength.

Heterologous expression of a Streptomyces cyaneus laccase for biomass modification applications

Laccases are used for the conversion of biomass into fermentable sugars but it is difficult to produce high yields of active laccases in heterologous expression systems. We overcame this challenge by expressing Streptomyces cyaneus CECT 3335 laccase in Escherichia coli (ScLac) and we achieved a yield of up to 104 mg L-1 following purification by one-step affinity chromatography. Stability and activity assays using simple lignin model substrates showed that the purified enzyme preparation was active over a broad pH range and at high temperatures, suggesting it would be suitable for biomass degradation. The reusability of ScLac was also demonstrated by immobilizing the enzyme on agarose beads with a binding yield of 33%, and by the synthesis of cross-linked enzyme aggregates with an initial activity recovery of 72%.

Pretreatment of agricultural biomass for anaerobic digestion: Current state and challenges

The anaerobic digestion (AD) of agricultural biomass is an attractive second generation biofuel with potential environmental and economic benefits. Most agricultural biomass contains lignocellulose which requires pretreatment prior to AD. For optimization, the pretreatment methods need to be specific to the characteristics of the biomass feedstock. In this review, cereal residue, fruit and vegetable wastes, grasses and animal manure were selected as the agricultural biomass candidates, and the fundamentals and current state of various pretreatment methods used for AD of these feedstocks were investigated. Several nonconventional methods (electrical, ionic liquid-based chemicals, ruminant biological pretreatment) offer potential as targeted pretreatments of lignocellulosic biomass, but each comes with its own challenges. Pursuing an energy-intensive route, a combined bioethanol-biogas production could be a promising a second biofuel refinery option, further emphasizing the importance of pretreatment when lignocellulosic feedstock is used.

Effect of Laccase-Mediated Biopolymer Grafting on Kraft Pulp Fibers for Enhancing Paper's Mechanical Properties

High-resistance paper was manufactured by laccase-grafting of carboxymethyl cellulose (CMC) and chitosan (CPX) on Kraft pulp fiber. The reaction was mediated in the presence of laccase by one of the following polyphenols in the presence of air: gallic acid (GA), vanillic acid (VA) and catechol (1,2–DHB). Enzyme was added at constant loading (24 kg ton⁻¹), 1% pulp consistency, 0.005% CMC, pH = 6.3 ± 0.5 and 2 mM of mediator. CPX content was assessed at two levels (0% and 0.005%). Treated pulps were analyzed by different mechanical tests (ring crush, mullen, corrugating medium test (CMT) flat crush of corrugating medium test and tension). An improvement in these parameters was obtained by biopolymer coupling and selected mediator. When using GA, three parameters increased more than 40%, while ring crush increased 120%. For the case of VA, properties were enhanced from 74% to 88% when CPX was added. For 1,2–DHB, there was not found a statistically significant difference between the results in the presence of CPX. Scanning electron microscopy, confocal microscopy, FTIR and ¹³C NMR were used in all papers in order to evaluate grafting. Hence, it was possible to correlate polymerization with an improvement of paper’s mechanical properties.

Laccase: a multi-purpose biocatalyst at the forefront of biotechnology

Laccases are multicopper containing enzymes capable of performing one electron oxidation of a broad range of substrates. Using molecular oxygen as the final electron acceptor, they release only water as a by-product, and as such, laccases are eco-friendly, versatile biocatalysts that have generated an enormous biotechnological interest. Indeed, this group of enzymes has been used in different industrial fields for very diverse purposes, from food additive and beverage processing to biomedical diagnosis, and as cross-linking agents for furniture construction or in the production of biofuels. Laccases have also been studied intensely in nanobiotechnology for the development of implantable biosensors and biofuel cells. Moreover, their capacity to transform complex xenobiotics makes them useful biocatalysts in enzymatic bioremediation. This review summarizes the most significant recent advances in the use of laccases and their future perspectives in biotechnology.

Nanopaper Properties and Adhesive Performance of Microfibrillated Cellulose from Different (Ligno-)Cellulosic Raw Materials

The self-adhesive potential of nanocellulose from aqueous cellulosic suspensions is of interest with regard to a potential replacement of synthetic adhesives. In order to evaluate the performance of microfibrillated cellulose from different (ligno-)cellulosic raw materials for this purpose, softwood and hardwood powder were fibrillated and compared to sugar beet pulp as a representative non-wood cellulose resource, and conventional microfibrillated cellulose produced from bleached pulp. An alkali pre-treatment of woody and sugar beet raw materials enhanced the degree of fibrillation achieved, same as TEMPO-mediated oxidation of microfibrillated cellulose. Nanopapers produced from fibrillated material showed highly variable density and mechanical performance, demonstrating that properties may be tuned by the choice of raw material. While nanopaper strength was highest for TEMPO-oxidated microfibrillated cellulose, fibrillated untreated sugar beet pulp showed the best adhesive performance. Different microscopic methods (AFM, SEM, light microscopy) examined the interface between wood and fibrillated material, showing particular distinctions to commercial adhesives. It is proposed that fibrillated material suspensions, which achieve bond strength up to 60% of commercial urea-formaldehyde adhesive, may provide a viable solution to bio-based adhesives in certain applications where wet-strength is not an issue.