Impact of the Copper Second Coordination Sphere on Catalytic Performance and Substrate Specificity of a Bacterial Lytic Polysaccharide Monooxygenase.

Lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of glycosidic bonds in recalcitrant polysaccharides, such as cellulose and chitin, using a single copper cofactor bound in a conserved histidine brace with a more variable second coordination sphere. Cellulose-active LPMOs in the fungal AA9 family and in a subset of bacterial AA10 enzymes contain a His-Gln-Tyr second sphere motif, whereas other cellulose-active AA10s have an Arg-Glu-Phe motif. To shine a light on the impact of this variation, we generated single, double, and triple mutations changing the His216-Gln219-Tyr221 motif in cellulose- and chitin-oxidizing MaAA10B toward Arg-Glu-Phe. These mutations generally reduced enzyme performance due to rapid inactivation under turnover conditions, showing that catalytic fine-tuning of the histidine brace is complex and that the roles of these second sphere residues are strongly interconnected. Studies of copper reactivity showed remarkable effects, such as an increase in oxidase activity following the Q219E mutation and a strong dependence of this effect on the presence of Tyr at position 221. In reductant-driven reactions, differences in oxidase activity, which lead to different levels of in situ generated H2O2, correlated with differences in polysaccharide-degrading ability. The single Q219E mutant displayed a marked increase in activity on chitin in both reductant-driven reactions and reactions fueled by exogenously added H2O2. Thus, it seems that the evolution of substrate specificity in LPMOs involves both the extended substrate-binding surface and the second coordination sphere.

Mutational dissection of a hole hopping route in a lytic polysaccharide monooxygenase (LPMO).

Oxidoreductases have evolved tyrosine/tryptophan pathways that channel highly oxidizing holes away from the active site to avoid damage. Here we dissect such a pathway in a bacterial LPMO, member of a widespread family of C-H bond activating enzymes with outstanding industrial potential. We show that a strictly conserved tryptophan is critical for radical formation and hole transference and that holes traverse the protein to reach a tyrosine-histidine pair in the protein's surface. Real-time monitoring of radical formation reveals a clear correlation between the efficiency of hole transference and enzyme performance under oxidative stress. Residues involved in this pathway vary considerably between natural LPMOs, which could reflect adaptation to different ecological niches. Importantly, we show that enzyme activity is increased in a variant with slower radical transference, providing experimental evidence for a previously postulated trade-off between activity and redox robustness.

Exploring class III cellobiose dehydrogenase: sequence analysis and optimized recombinant expression.

BACKGROUND: Cellobiose dehydrogenase (CDH) is an extracellular fungal oxidoreductase with multiple functions in plant biomass degradation. Its primary function as an auxiliary enzyme of lytic polysaccharide monooxygenase (LPMO) facilitates the efficient depolymerization of cellulose, hemicelluloses and other carbohydrate-based polymers. The synergistic action of CDH and LPMO that supports biomass-degrading hydrolases holds significant promise to harness renewable resources for the production of biofuels, chemicals, and modified materials in an environmentally sustainable manner. While previous phylogenetic analyses have identified four distinct classes of CDHs, only class I and II have been biochemically characterized so far. RESULTS: Following a comprehensive database search aimed at identifying CDH sequences belonging to the so far uncharacterized class III for subsequent expression and biochemical characterization, we have curated an extensive compilation of putative CDH amino acid sequences. A sequence similarity network analysis was used to cluster them into the four distinct CDH classes. A total of 1237 sequences encoding putative class III CDHs were extracted from the network and used for phylogenetic analyses. The obtained phylogenetic tree was used to guide the selection of 11 cdhIII genes for recombinant expression in Komagataella phaffii. A small-scale expression screening procedure identified a promising cdhIII gene originating from the plant pathogen Fusarium solani (FsCDH), which was selected for expression optimization by signal peptide shuffling and subsequent production in a 5-L bioreactor. The purified FsCDH exhibits a UV-Vis spectrum and enzymatic activity similar to other characterized CDH classes. CONCLUSION: The successful production and functional characterization of FsCDH proved that class III CDHs are catalytical active enzymes resembling the key properties of class I and class II CDHs. A detailed biochemical characterization based on the established expression and purification strategy can provide new insights into the evolutionary process shaping CDHs and leading to their differentiation into the four distinct classes. The findings have the potential to broaden our understanding of the biocatalytic application of CDH and LPMO for the oxidative depolymerization of polysaccharides.

The other side of the coin: systemic effects of Serendipita indica root colonization on development of sedentary plant-parasitic nematodes in Arabidopsis thaliana.

MAIN CONCLUSION: Upon systemic S. indica colonization in split-root system cyst and root-knot nematodes benefit from endophyte-triggered carbon allocation and altered defense responses what significantly facilitates their development in A. thaliana. Serendipita indica is an endophytic fungus that establishes mutualistic relationships with different plants including Arabidopsis thaliana. It enhances host's growth and resistance to different abiotic and biotic stresses such as infestation by the cyst nematode Heterodera schachtii (CN). In this work, we show that S. indica also triggers similar direct reduction in development of the root-knot nematode Meloidogyne javanica (RKN) in A. thaliana. Further, to mimick the natural situation occurring frequently in soil where roots are unequally colonized by endophytes we used an in vitro split-root system with one half of A. thaliana root inoculated with S. indica and the other half infected with CN or RKN, respectively. Interestingly, in contrast to direct effects, systemic effects led to an increase in number of both nematodes. To elucidate this phenomenon, we focused on sugar metabolism and defense responses in systemic non-colonized roots of plants colonized by S. indica. We analyzed the expression of several SUSs and INVs as well as defense-related genes and measured sugar pools. The results show a significant downregulation of PDF1.2 as well as slightly increased sucrose levels in the non-colonized half of the root in three-chamber dish. Thus, we speculate that, in contrast to direct effects, both nematode species benefit from endophyte-triggered carbon allocation and altered defense responses in the systemic part of the root, which promotes their development. With this work, we highlight the complexity of this multilayered tripartite relationship and deliver new insights into sugar metabolism and plant defense responses during S. indica-nematode-plant interaction.

The application of bacteria-derived dehydrogenases and oxidases in the synthesis of gold nanoparticles.

In this work the green synthesis of gold nanoparticles (Au-NPs) using the oxidoreductive enzymes Myriococcum thermophilum cellobiose dehydrogenase (Mt CDH), Glomerella cingulata glucose dehydrogenase (Gc GDH), and Aspergillus niger glucose oxidase (An GOX)) as bioreductants was investigated. The influence of reaction conditions on the synthesis of Au-NPs was examined and optimised. The reaction kinetics and the influence of Au ions on the reaction rate were determined. Based on the kinetic study, the mechanism of Au-NP synthesis was proposed. The Au-NPs were characterized by UV-Vis spectroscopy and transmission electron microscopy (TEM). The surface plasmon resonance (SPR) absorption peaks of the Au-NPs synthesised with Mt CDH and Gc GDH were observed at 535 nm, indicating an average size of around 50 nm. According to the image analysis performed on a TEM micrograph, the Au-NPs synthesized with Gc GDH have a spherical shape with an average size of 2.83 and 6.63 nm after 24 and 48 h of the reaction, respectively. KEY POINTS: • The Au NPs were synthesised by the action of enzymes CDH and GDH. • The synthesis of Au-NPs by CDH is related to the oxidation of cellobiose. • The synthesis of Au-NPs by GDH was not driven by the reaction kinetic.

Electrochemical Monitoring of Heterogeneous Peroxygenase Reactions Unravels LPMO Kinetics.

Biological conversion of plant biomass depends on peroxygenases and peroxidases acting on insoluble polysaccharides and lignin. Among these are cellulose- and hemicellulose-degrading lytic polysaccharide monooxygenases (LPMOs), which have revolutionized our concept of biomass degradation. Major obstacles limiting mechanistic and functional understanding of these unique peroxygenases are their complex and insoluble substrates and the hard-to-measure H2O2 consumption, resulting in the lack of suitable kinetic assays. We report a versatile and robust electrochemical method for real-time monitoring and kinetic characterization of LPMOs and other H2O2-dependent interfacial enzymes based on a rotating disc electrode for the sensitive and selective quantitation of H2O2 at biologically relevant concentrations. The H2O2 sensor works in suspensions of insoluble substrates as well as in homogeneous solutions. Our characterization of multiple LPMOs provides unprecedented insights into the substrate specificity, kinetics, and stability of these enzymes. High turnover and total turnover numbers demonstrate that LPMOs are fast and durable biocatalysts.

Amino Acid Residues Controlling Domain Interaction and Interdomain Electron Transfer in Cellobiose Dehydrogenase.

The function of cellobiose dehydrogenase (CDH) in biosensors, biofuel cells, and as a physiological redox partner of lytic polysaccharide monooxygenase (LPMO) is based on its role as an electron donor. Before donating electrons to LPMO or electrodes, an interdomain electron transfer from the catalytic FAD-containing dehydrogenase domain to the electron shuttling cytochrome domain of CDH is required. This study investigates the role of two crucial amino acids located at the dehydrogenase domain on domain interaction and interdomain electron transfer by structure-based engineering. The electron transfer kinetics of wild-type Myriococcum thermophilum CDH and its variants M309A, R698S, and M309A/R698S were analyzed by stopped-flow spectrophotometry and structural effects were studied by small-angle X-ray scattering. The data show that R698 is essential to pull the cytochrome domain close to the dehydrogenase domain and orient the heme propionate group towards the FAD, while M309 is an integral part of the electron transfer pathway - its mutation reducing the interdomain electron transfer 10-fold. Structural models and molecular dynamics simulations pinpoint the action of these two residues on the domain interaction and interdomain electron transfer.

Molecular modelling and site-directed mutagenesis provide insight into saccharide pyruvylation by the Paenibacillus alvei CsaB enzyme.

Pyruvylation is a biologically versatile but mechanistically unexplored saccharide modification. 4,6-Ketal pyruvylated N-acetylmannosamine within bacterial secondary cell wall polymers serves as a cell wall anchoring epitope for proteins possessing a terminal S-layer homology domain trimer. The pyruvyltransferase CsaB from Paenibacillus alvei served as a model to investigate the structural basis of the pyruvyltransfer reaction by a combination of molecular modelling and site-directed mutagenesis together with an enzyme assay using phosphoenolpyruvate (PEP; donor) and synthetic ß-D-ManNAc-(1 → 4)-α-D-GlcNAc-diphosphoryl-11-phenoxyundecyl (acceptor). CsaB protein structure modelling was done using Phyre2 and I-Tasser based on the partial crystal structure of the Schizosaccharomyces pombe pyruvyltransferase Pvg1p and by AlphaFold. The models informed the construction of twelve CsaB mutants targeted at plausible PEP and acceptor binding sites and KM and kcat values were determined to evaluate the mutants, indicating the importance of a loop region for catalysis. R148, H308 and K328 were found to be critical to PEP binding and insight into acceptor binding was obtained from an analysis of Y14 and F16 mutants, confirming the modelled binding sites and interactions predicted using Molecular Operating Environment. These data lay the basis for future mechanistic studies of saccharide pyruvylation as a novel target for interference with bacterial cell wall assembly.

Enzymatic Pretreatment of Plant Cells for Oil Extraction.

Oil from oilseeds can be extracted by mechanical extraction (pressing), aqueous extraction, or by extraction with organic solvents. Although solvent extraction is the most efficient method, organic solvents are a potential hazard to the life and health for workers as well as to the environment, when solvent vapours are released and act as air pollutant with a high ozone-forming potential. Pressing is safer, environmentally friendly, and it preserves valuable natural components in the resulting oils. The problems associated with pressing are the high energy consumption and the lower yield of oil extraction, because the applied mechanical force does not completely destroy the structural cell components storing the oil. In seed cells, the oil is contained in the form of lipid bodies (oleosomes) that are surrounded by a phospholipid monolayer with a protein layer on the surface. These lipid bodies are further protected by the seed cell walls consisting mainly of polysaccharides such as pectins, hemicelluloses and cellulose, but also of glycoproteins. The use of hydrolases to degrade these barriers is a promising pretreatment strategy to support mechanical extraction and improve the oil yield. It is advisable to use a combination of enzymes with different activities when considering the multicompartment and multicomponent structure of oilseed cells. This article gives an overview of the microstructure and composition of oilseed cells, reviews enzymes capable of destroying oil containing cell compartments, and summarizes the main parameters of enzymatic treatment procedures, such as the composition of the enzyme cocktail, the amount of enzyme and water used, temperature, pH, and the duration of the treatment. Finally, it analyzes the efficiency of proteolytic, cellulolytic and pectolytic enzyme pretreatment to increase the yield of mechanically extracted oil from various types of vegetable raw materials with the main focus on oilseeds.

Interdomain Linker of the Bioelecrocatalyst Cellobiose Dehydrogenase Governs the Electron Transfer.

Direct bioelectrocatalysis applied in biosensors, biofuel cells, and bioelectrosynthesis is based on an efficient electron transfer between enzymes and electrodes in the absence of redox mediators. Some oxidoreductases are capable of direct electron transfer (DET), while others achieve the enzyme to electrode electron transfer (ET) by employing an electron-transferring domain. Cellobiose dehydrogenase (CDH) is the most-studied multidomain bioelectrocatalyst and features a catalytic flavodehydrogenase domain and a mobile, electron-transferring cytochrome domain connected by a flexible linker. The ET to the physiological redox partner lytic polysaccharide monooxygenase or, ex vivo, electrodes depends on the flexibility of the electron transferring domain and its connecting linker, but the regulatory mechanism is little understood. Studying the linker sequences of currently characterized CDH classes we observed that the inner, mobile linker sequence is flanked by two outer linker regions that are in close contact with the adjacent domain. A function-based definition of the linker region in CDH is proposed and has been verified by rationally designed variants of Neurospora crassa CDH. The effect of linker length and its domain attachment on electron transfer rates has been determined by biochemical and electrochemical methods, while distances between the domains of CDH variants were computed. This study elucidates the regulatory mechanism of the interdomain linker on electron transfer by determining the minimum linker length, observing the effects of elongated linkers, and testing the covalent stabilization of a linker part to the flavodehydrogenase domain. The evolutionary guided, rational design of the interdomain linker provides a strategy to optimize electron transfer rates in multidomain enzymes and maximize their bioelectrocatalytic performance.

Resolving domain positions of cellobiose dehydrogenase by small angle X-ray scattering.

The interdomain electron transfer (IET) between the catalytic flavodehydrogenase domain and the electron-transferring cytochrome domain of cellobiose dehydrogenase (CDH) plays an essential role in biocatalysis, biosensors and biofuel cells, as well as in its natural function as an auxiliary enzyme of lytic polysaccharide monooxygenase. We investigated the mobility of the cytochrome and dehydrogenase domains of CDH, which is hypothesised to limit IET in solution by small angle X-ray scattering (SAXS). CDH from Myriococcum thermophilum (syn. Crassicarpon hotsonii, syn. Thermothelomyces myriococcoides) was probed by SAXS to study the CDH mobility at different pH and in the presence of divalent cations. By comparison of the experimental SAXS data, using pair-distance distribution functions and Kratky plots, we show an increase in CDH mobility at higher pH, indicating alterations of domain mobility. To further visualise CDH movement in solution, we performed SAXS-based multistate modelling. Glycan structures present on CDH partially masked the resulting SAXS shapes, we diminished these effects by deglycosylation and studied the effect of glycoforms by modelling. The modelling shows that with increasing pH, the cytochrome domain adopts a more flexible state with significant separation from the dehydrogenase domain. On the contrary, the presence of calcium ions decreases the mobility of the cytochrome domain. Experimental SAXS data, multistate modelling and previously reported kinetic data show how pH and divalent ions impact the closed state necessary for the IET governed by the movement of the CDH cytochrome domain.

Electrochemical and biosensing properties of an FAD-dependent glucose dehydrogenase from Trichoderma virens.

We investigated the bioelectrochemical properties of an FAD-dependent glucose dehydrogenase from Trichoderma virens (TvGDH) and its electrochemical behaviour when immobilized on a graphite electrode. TvGDH was recently shown to have an unusual substrate spectrum and to prefer maltose over glucose as substrate, and hence could be of interest as recognition element in a maltose sensor. In this study, we determined the redox potential of TvGDH, which is -0.268 ± 0.007 V vs. SHE, and advantageously low to be used with many redox mediators or redox polymers. The enzyme was entrapped in, and wired by an osmium redox polymer (poly(1-vinylimidazole-co-allylamine)-{[Os(2,2'-bipyridine)2Cl]Cl}) with formal redox potential of +0.275 V vs. Ag|AgCl via poly(ethylene glycol) diglycidyl ether crosslinking onto a graphite electrode. When the TvGDH-based biosensor was tested with maltose it showed a sensitivity of 1.7 µA mM-1cm-2, a linear range of 0.5-15 mM, and a detection limit of 0.45 mM. Furthermore, it gave the lowest apparent Michaelis-Menten constant (KM app) of 19.2 ± 1.5 mM towards maltose when compared to other sugars. The biosensor is also able to detect other saccharides including glucose, maltotriose and galactose, these however also interfere with maltose sensing.

Interface engineering of cellobiose dehydrogenase improves interdomain electron transfer.

Cellobiose dehydrogenase (CDH) is a bioelectrocatalyst that enables direct electron transfer (DET) in biosensors and biofuel cells. The application of this bidomain hemoflavoenzyme for physiological glucose measurements is limited by its acidic pH optimum and slow interdomain electron transfer (IET) at pH 7.5. The reason for this rate-limiting electron transfer step is electrostatic repulsion at the interface between the catalytic dehydrogenase domain and the electron mediating cytochrome domain (CYT). We applied rational interface engineering to accelerate the IET for the pH prevailing in blood or interstitial fluid. Phylogenetic and structural analyses guided the design of 17 variants in which acidic amino acids were mutated at the CYT domain. Five mutations (G71K, D160K, Q174K, D177K, M180K) increased the pH optimum and IET rate. Structure-based analysis of the variants suggested two mechanisms explaining the improvements: electrostatic steering and stabilization of the closed state by hydrogen bonding. Combining the mutations into six combinatorial variants with up to five mutations shifted the pH optimum from 4.5 to 7.0 and increased the IET at pH 7.5 over 12-fold from 0.1 to 1.24 s-1 . While the mutants sustained a high enzymatic activity and even surpassed the IET of the wild-type enzyme, the accumulated positive charges on the CYT domain decreased DET, highlighting the importance of CYT for IET and DET. This study shows that interface engineering is an effective strategy to shift the pH optimum and improve the IET of CDH, but future work needs to maintain the DET of the CYT domain for bioelectronic applications.

AA16 Oxidoreductases Boost Cellulose-Active AA9 Lytic Polysaccharide Monooxygenases from Myceliophthora thermophila.

Copper-dependent lytic polysaccharide monooxygenases (LPMOs) classified in Auxiliary Activity (AA) families are considered indispensable as synergistic partners for cellulolytic enzymes to saccharify recalcitrant lignocellulosic plant biomass. In this study, we characterized two fungal oxidoreductases from the new AA16 family. We found that MtAA16A from Myceliophthora thermophila and AnAA16A from Aspergillus nidulans did not catalyze the oxidative cleavage of oligo- and polysaccharides. Indeed, the MtAA16A crystal structure showed a fairly LPMO-typical histidine brace active site, but the cellulose-acting LPMO-typical flat aromatic surface parallel to the histidine brace region was lacking. Further, we showed that both AA16 proteins are able to oxidize low-molecular-weight reductants to produce H2O2. The oxidase activity of the AA16s substantially boosted cellulose degradation by four AA9 LPMOs from M. thermophila (MtLPMO9s) but not by three AA9 LPMOs from Neurospora crassa (NcLPMO9s). The interplay with MtLPMO9s is explained by the H2O2-producing capability of the AA16s, which, in the presence of cellulose, allows the MtLPMO9s to optimally drive their peroxygenase activity. Replacement of MtAA16A by glucose oxidase (AnGOX) with the same H2O2-producing activity could only achieve less than 50% of the boosting effect achieved by MtAA16A, and earlier MtLPMO9B inactivation (6 h) was observed. To explain these results, we hypothesized that the delivery of AA16-produced H2O2 to the MtLPMO9s is facilitated by protein-protein interaction. Our findings provide new insights into the functions of copper-dependent enzymes and contribute to a further understanding of the interplay of oxidative enzymes within fungal systems to degrade lignocellulose.

Continuous ex vivo glucose sensing in human physiological fluids using an enzymatic sensor in a vein replica.

Managing blood glucose can affect important clinical outcomes during the intraoperative phase of surgery. However, currently available instruments for glucose monitoring during surgery are few and not optimized for the specific application. Here we report an attempt to exploit an enzymatic sensor in a vein replica that could continuously monitor glucose level in an authentic human bloodstream. First, detailed investigations of the superficial venous systems of volunteers were carried out using ocular and palpating examinations, as well as advanced ultrasound measurements. Second, a tubular glucose-sensitive biosensor mimicking a venous system was designed and tested. Almost ideal linear dependence of current output on glucose concentration in phosphate buffer saline was obtained in the range 2.2-22.0 mM, whereas the dependence in human plasma was less linear. Finally, the developed biosensor was investigated in whole blood under homeostatic conditions. A specific correlation was found between the current output and glucose concentration at the initial stage of the biodevice operation. However, with time, blood coagulation during measurements negatively affected the performance of the biodevice. When the experimental results were remodeled to predict the response without the influence of blood coagulation, the sensor output closely followed the blood glucose level.

Continuous photometric activity assays for lytic polysaccharide monooxygenase-Critical assessment and practical considerations.

Lytic polysaccharide monooxygenase (LPMO) is a monocopper-dependent enzyme that cleaves glycosidic bonds by using an oxidative mechanism. In nature, they act in concert with cellobiohydrolases to facilitate the efficient degradation of lignocellulosic biomass. After more than a decade of LPMO research, it has become evident that LPMOs are abundant in all domains of life and fulfill a diverse range of biological functions. Independent of their biological function and the preferred polysaccharide substrate, studying and characterizing LPMOs is tedious and so far mostly relied on the discontinuous analysis of the solubilized reaction products by HPLC/MS-based methods. In the absence of appropriate substrates, LPMOs can engage in two off-pathway reactions, i.e., an oxidase and a peroxidase-like activity. These futile reactions have been exploited to set up easy-to-use continuous spectroscopic assays. As the natural substrates of newly discovered LPMOs are often unknown, widely applicable, simple, reliable, and robust spectroscopic assays are required to monitor LPMO expression and to perform initial biochemical characterizations, e.g., thermal stability measurements. Here we provide detailed descriptions and practical protocols to perform continuous photometric assays using either 2,6-dimethoxyphenol (2,6-DMP) or hydrocoerulignone as colorimetric substrates as a broadly applicable assay for a range of LPMOs. In addition, a turbidimetric measurement is described as the currently only method available to continuously monitor LPMOs acting on amorphous cellulose.

Mutations Increasing Cofactor Affinity, Improve Stability and Activity of a Baeyer-Villiger Monooxygenase.

The typically low thermodynamic and kinetic stability of enzymes is a bottleneck for their application in industrial synthesis. Baeyer-Villiger monooxygenases, which oxidize ketones to lactones using aerial oxygen, among other activities, suffer particularly from these instabilities. Previous efforts in protein engineering have increased thermodynamic stability but at the price of decreased activity. Here, we solved this trade-off by introducing mutations in a cyclohexanone monooxygenase from Acinetobacter sp., guided by a combination of rational and structure-guided consensus approaches. We developed variants with improved activity (1.5- to 2.5-fold) and increased thermodynamic (+5 °C T m) and kinetic stability (8-fold). Our analysis revealed a crucial position in the cofactor binding domain, responsible for an 11-fold increase in affinity to the flavin cofactor, and explained using MD simulations. This gain in affinity was compatible with other mutations. While our study focused on a particular model enzyme, previous studies indicate that these findings are plausibly applicable to other BVMOs, and possibly to other flavin-dependent monooxygenases. These new design principles can inform the development of industrially robust, flavin-dependent biocatalysts for various oxidations.

Investigating lytic polysaccharide monooxygenase-assisted wood cell wall degradation with microsensors.

Lytic polysaccharide monooxygenase (LPMO) supports biomass hydrolysis by increasing saccharification efficiency and rate. Recent studies demonstrate that H2O2 rather than O2 is the cosubstrate of the LPMO-catalyzed depolymerization of polysaccharides. Some studies have questioned the physiological relevance of the H2O2-based mechanism for plant cell wall degradation. This study reports the localized and time-resolved determination of LPMO activity on poplar wood cell walls by measuring the H2O2 concentration in their vicinity with a piezo-controlled H2O2 microsensor. The investigated Neurospora crassa LPMO binds to the inner cell wall layer and consumes enzymatically generated H2O2. The results point towards a high catalytic efficiency of LPMO at a low H2O2 concentration that auxiliary oxidoreductases in fungal secretomes can easily generate. Measurements with a glucose microbiosensor additionally demonstrate that LPMO promotes cellobiohydrolase activity on wood cell walls and plays a synergistic role in the fungal extracellular catabolism and in industrial biomass degradation.

Application of Causality Modelling for Prediction of Molecular Properties for Textile Dyes Degradation by LPMO.

The textile industry is one of the largest water-polluting industries in the world. Due to an increased application of chromophores and a more frequent presence in wastewaters, the need for an ecologically favorable dye degradation process emerged. To predict the decolorization rate of textile dyes with Lytic polysaccharide monooxygenase (LPMO), we developed, validated, and utilized the molecular descriptor structural causality model (SCM) based on the decision tree algorithm (DTM). Combining mathematical models and theories with decolorization experiments, we have elucidated the most important molecular properties of the dyes and confirm the accuracy of SCM model results. Besides the potential utilization of the developed model in the treatment of textile dye-containing wastewater, the model is a good base for the prediction of the molecular properties of the molecule. This is important for selecting chromophores as the reagents in determining LPMO activities. Dyes with azo- or triarylmethane groups are good candidates for colorimetric LPMO assays and the determination of LPMO activity. An adequate methodology for the LPMO activity determination is an important step in the characterization of LPMO properties. Therefore, the SCM/DTM model validated with the 59 dyes molecules is a powerful tool in the selection of adequate chromophores as reagents in the LPMO activity determination and it could reduce experimentation in the screening experiments.