Biodelignification of lignocellulose using ligninolytic enzymes from white-rot fungi

Effects of different proportions of fruit tree branches on nicotine content and microbial diversity during composting of tobacco waste

Adding fruit tree branches to the compost pile in appropriate proportions is one of the methods used to address the challenge of tobacco waste recycling. However, the effects of different proportions of fruit tree branches on nicotine concentration and microbial diversity during tobacco waste composting have not been reported. In this study, a composting system with tobacco waste, cow dung, and fruit tree branches was established in a laboratory fermenter to assess the impact of adding 10%, 20%, and 30% fruit tree branches on quantity changes. In addition, the relationships between nicotine degradation, compost properties, enzyme activities, and microbial diversities were determined using biochemical assay methods and high-throughput sequencing. The results showed that adding appropriate proportions of fruit branch segments affected changes in physical and chemical properties during composting and promoted tobacco waste compost maturity. Aerobic composting effectively degraded nicotine in tobacco waste. Increased proportions of fruit branch segments led to elevations in nicotine degradation rates and enzyme activities related to lignocellulose degradation. The addition of fruit branches influenced the relative abundance and species of dominant bacteria and fungi at the phylum and genus levels. However, it did not significantly affect the relative abundance of the main bacterial genera involved in nicotine degradation. Nevertheless, it reduced the sensitivity of enzyme activity to nicotine content within heaps, increasing reliance on total nitrogen changes. The results of this study provide a theoretical basis for the utilization of tobacco waste in composting systems and indicate that fruit tree branches can enhance nicotine degradation efficiency during tobacco waste composting.

Sequence and structure analyses of lytic polysaccharide monooxygenases mined from metagenomic DNA of humus samples around white-rot fungi in Cuc Phuong tropical forest, Vietnam

Background

White-rot fungi and bacteria communities are unique ecosystems with different types of symbiotic interactions occurring during wood decomposition, such as cooperation, mutualism, nutritional competition, and antagonism. The role of chitin-active lytic polysaccharide monooxygenases (LPMOs) in these symbiotic interactions is the subject of this study.

Method

In this study, bioinformatics tools were used to analyze the sequence and structure of putative LPMOs mined by hidden Markov model (HMM) profiles from the bacterial metagenomic DNA database of collected humus samples around white-rot fungi in Cuc Phuong primary forest, Vietnam. Two genes encoding putative LPMOs were expressed in E. coli and purified for enzyme activity assay.

Result

Thirty-one full-length proteins annotated as putative LPMOs according to HMM profiles were confirmed by amino acid sequence comparison. The comparison results showed that although the amino acid sequences of the proteins were very different, they shared nine conserved amino acids, including two histidine and one phenylalanine that characterize the H1-Hx-Yz motif of the active site of bacterial LPMOs. Structural analysis of these proteins revealed that they are multidomain proteins with different functions. Prediction of the catalytic domain 3-D structure of these putative LPMOs using Alphafold2 showed that their spatial structures were very similar in shape, although their protein sequences were very different. The results of testing the activity of proteins GL0247266 and GL0183513 show that they are chitin-active LPMOs. Prediction of the 3-D structures of these two LPMOs using Alphafold2 showed that GL0247266 had five functional domains, while GL0183513 had four functional domains, two of which that were similar to the GbpA_2 and GbpA_3 domains of protein GbpA of Vibrio cholerae bacteria. The GbpA_2 - GbpA_3 complex was also detected in 11 other proteins. Based on the structural characteristics of functional domains, it is possible to hypothesize the role of chitin-active GbpA-like LPMOs in the relationship between fungal and bacterial communities coexisting on decomposing trees in primary forests.

Nature's Plastic Predators: A Comprehensive and Bibliometric Review of Plastivore Insects

Unprecedented plastic production has resulted in over six billion tons of harmful waste. Certain insect taxa emerge as potential agents of plastic biodegradation. Through a comprehensive manual and bibliometric literature analysis, this review analyses and consolidates the growing literature related to insect-mediated plastic breakdown. Over 23 insect species, representing Coleoptera, Lepidoptera, and 4 other orders, have been identified for their capacity to consume plastic polymers. Natural and synthetic polymers exhibit high-level similarities in molecular structure and properties. Thus, in conjunction with comparative genomics studies, we link plastic-degrading enzymatic capabilities observed in certain insects to the exaptation of endogenous enzymes originally evolved for digesting lignin, cellulose, beeswax, keratin and chitin from their native dietary substrates. Further clarification is necessary to distinguish mineralisation from physicochemical fragmentation and to differentiate microbiome-mediated degradation from direct enzymatic reactions by insects. A bibliometric analysis of the exponentially growing body of literature showed that leading research is emerging from China and the USA. Analogies between natural and synthetic polymer's degradation pathways will inform engineering robust enzymes for practical plastic bioremediation applications. By aggregating, analysing, and interpreting published insights, this review consolidates our mechanistic understanding of insects as a potential natural solution to the escalating plastic waste crisis.

Lignocellulolytic Enzymes Production by Four Wild Filamentous Fungi for Olive Stones Valorization: Comparing Three Fermentation Regimens

Lignocellulolytic enzymes play a crucial role in efficiently converting lignocellulose into valuable platform molecules in various industries. However, they are limited by their production yields, costs, and stability. Consequently, their production by producers adapted to local environments and the choice of low-cost raw materials can address these limitations. Due to the large amounts of olive stones (OS) generated in Morocco which are still undervalued, Penicillium crustosum, Fusarium nygamai, Trichoderma capillare, and Aspergillus calidoustus, are cultivated under different fermentation techniques using this by-product as a local lignocellulosic substrate. Based on a multilevel factorial design, their potential to produce lignocellulolytic enzymes during 15 days of dark incubation was evaluated. The results revealed that P. crustosum expressed a maximum total cellulase activity of 10.9 IU/ml under sequential fermentation (SF) and 3.6 IU/ml of β-glucosidase activity under submerged fermentation (SmF). F. nygamai recorded the best laccase activity of 9 IU/ml under solid-state fermentation (SSF). Unlike T. capillare, SF was the inducive culture for the former activity with 7.6 IU/ml. A. calidoustus produced, respectively, 1,009 μg/ml of proteins and 11.5 IU/ml of endoglucanase activity as the best results achieved. Optimum cellulase production took place after the 5th day under SF, while ligninases occurred between the 9th and the 11th days under SSF. This study reports for the first time the lignocellulolytic activities of F. nygamai and A. calidoustus. Furthermore, it underlines the potential of the four fungi as biomass decomposers for environmentally-friendly applications, emphasizing the efficiency of OS as an inducing substrate for enzyme production.

Effects of Orange Peel Extract on Laccase Activity and Gene Expression in Trametes versicolor

The genome of Trametes versicolor encodes multiple laccase isozymes, the expression of which is responsive to various conditions. Here, we set out to investigate the potential of orange peel extract as an inducer of laccase production in this white-rot fungus, in comparison to the previously identified inducing chemical compound, veratryl alcohol. For four geographically distinct T. versicolor strains, a positive correlation has been observed between their oxidative activity and incubation time in liquid cultures. The addition of 20% orange peel extract or 5 mM veratryl alcohol caused a rapid increase in the oxidative potential of T. versicolor M99 after 24 h, with a more pronounced effect observed for the orange peel extract. To elucidate the underlying molecular mechanisms of the induced laccase activity, a transcriptional gene expression analysis was performed for the seven individual laccase genes in T. versicolor, revealing the upregulation of several laccase genes in response to the addition of each inducer. Notably, the gene encoding TvLac5 demonstrated a substantial upregulation in response to the addition of 20% orange peel extract, likely contributing to the observed increase in its oxidative potential. In conclusion, our results demonstrate that orange peels are a promising agro-industrial side stream for implementation as inducing agents in large-scale laccase production with T. versicolor.

Lignocellulosic biomass fertilizers: Production, characterization, and agri-applications

The growing focus on sustainable agriculture and optimal resource utilization has spurred investigations into lignocellulosic biomass as a potential source for producing environmentally friendly fertilizers. This paper reviews recent advancements in the production and application of innovative fertilizers derived from lignocellulose. It highlights potential in enhancing agricultural productivity and reducing environmental impacts such as carbon footprint and water pollution. The paper outlines various methods for conversion, highlighting the unique advantages of chemical, enzymatic, and microbiological processes, for converting lignocellulosic biomass into nutrient-rich fertilizers. The study compares the efficacy of lignocellulosic fertilizers to traditional fertilizers in promoting crop growth, enhancing soil health, and reducing nutrient losses. The results demonstrate the potential of lignocellulosic biomass-derived fertilizers in promoting resource efficiency and sustainable agriculture. While this research significantly contributes to the existing body of knowledge, further studies on long-term impacts and scalability are recommended for the development of innovative and sustainable agricultural practices.

Pathogenicity of monokaryotic and dikaryotic mycelia of Ganoderma boninense revealed via LC-MS-based metabolomics

This study compared the pathogenicity of monokaryotic (monokaryon) and dikaryotic (dikaryon) mycelia of the oil palm pathogen Ganoderma boninense via metabolomics approach. Ethyl acetate crude extracts of monokaryon and dikaryon were analysed by liquid chromatography quadrupole/time-of-flight-mass spectrometry (LC-Q/TOF-MS) coupled with multivariate data analysis using MetaboAnalyst. The mummichog algorithm was also used to identify the functional activities of monokaryon and dikaryon without a priori identification of all their secondary metabolites. Results revealed that monokaryon produced lesser fungal metabolites than dikaryon, suggesting that monokaryon had a lower possibility of inducing plant infection. These findings were further supported by the identified functional activities. Monokaryon exhibits tyrosine, phenylalanine, and tryptophan metabolism, which are important for fungal growth and development and to produce toxin precursors. In contrast, dikaryon exhibits the metabolism of cysteine and methionine, arginine and proline, and phenylalanine, which are important for fungal growth, development, virulence, and pathogenicity. As such, monokaryon is rendered non-pathogenic as it produces growth metabolites and toxin precursors, whereas dikaryon is pathogenic as it produces metabolites that are involved in fungal growth and pathogenicity. The LC-MS-based metabolomics approach contributes significantly to our understanding of the pathogenesis of Ganoderma boninense, which is essential for disease management in oil palm plantations.

Oxidative Machinery of basidiomycetes as potential enhancers in lignocellulosic biorefineries: A lytic polysaccharide monooxygenases approach

Basidiomycetes are renowned as highly effective decomposers of plant materials, due to their extensive array of oxidative enzymes, which enable them to efficiently break down complex lignocellulosic biomass structures. Among the oxidative machinery of industrially relevant basidiomycetes, the role of lytic polysaccharide monooxygenases (LPMO) in lignocellulosic biomass deconstruction is highlighted. So far, only a limited number of basidiomycetes LPMOs have been identified and heterologously expressed. These LPMOs have presented activity on cellulose and hemicellulose, as well as participation in the deconstruction of lignin. Expanding on this, the current review proposes both enzymatic and non-enzymatic mechanisms of LPMOs for biomass conversion, considering the significance of the Carbohydrate-Binding Modules and other C-terminal regions domains associated with their structure, which is involved in the deconstruction of lignocellulosic biomass.

Panapophenanthrin, a Rare Oligocyclic Diterpene from Panus strigellus

During the course of our search for biologically active secondary metabolites from fungal cultures, a new oligocyclic diterpenoidal derivative, panapophenanthrin (1), was isolated from Panus strigellus. In addition, two known metabolites, panepophenanthrin (2) and dihydrohypnophilin (3), were also obtained. The chemical structures of the isolated compounds were elucidated based on extensive 1D and 2D NMR spectral analyses together with high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The absolute configuration was determined through TDDFT-ECD calculations. All of the compounds were assessed for their antimicrobial and cytotoxic activities. Compounds 1 and 3 showed moderate to weak activities in the performed antimicrobial assays, while compound 1 exhibited potent cytotoxic activity against the mammalian cell lines mouse fibroblast (L929) and human endocervical adenocarcinoma (KB3.1).

White-rot fungi scavenge reactive oxygen species, which drives pH-dependent exo-enzymatic mechanisms and promotes CO2 efflux

Soil organic matter (SOM) decomposition mechanisms in rainforest ecosystems are governed by biotic and abiotic procedures which depend on available oxygen in the soil. White-rot fungi (WRF) play an important role in the primary decomposition of SOM via enzymatic mechanisms (biotic mechanism), which are linked to abiotic oxidative reactions (e.g., Fenton reaction), where both processes are dependent on reactive oxygen species (ROS) and soil pH variation, which has yet been studied. In humid temperate forest soils, we hypothesize that soil pH is a determining factor that regulates the production and consumption of ROS during biotic and abiotic SOM decomposition. Three soils from different parent materials and WRF inoculum were considered for this study: granitic (Nahuelbuta, Schizophyllum commune), metamorphic (Alerce Costero, Stereum hirsutum), and volcanic-allophanic (Puyehue, Galerina patagonica). CO₂ fluxes, lignin peroxidase, manganese peroxidase, and dye-decolorizing peroxidase levels were all determined. Likewise, the production of superoxide anion (O₂•-), hydrogen peroxide (H₂O₂), and hydroxyl radicals (•OH) were assessed in soils microcosms after 36 days of anaerobic incubation with WRF inoculum and induced Fenton reaction under pH variations ranging from 2.5 to 5.1. ROS significantly increased biotic and abiotic CO₂ emissions in all tested soils, according to the findings. The highest values (217.45 mg C kg^-1) were found during the anaerobic incubation of sterilized and inoculated soils with WRF at a natural pH of 4.5. At pH 4.0, the lowest levels of C mineralization (82 mg C kg^-1) were found in Nahuelbuta soil. Enzyme activities showed different trends as pH changed. The Fenton reaction consumed more H₂O₂ between pH 3 and 4, but less between pH 4.5 and 2.5. The mechanisms that oxidized SOM are extremely sensitive to variations in soil pH and the stability of oxidant radical and non-radical compounds, according to our findings.

Advances in the Physico-Chemical, Antimicrobial and Angiogenic Properties of Graphene-Oxide/Cellulose Nanocomposites for Wound Healing

Graphene oxide (GO) and its reduced form (rGO) have recently attracted a fascinating interest due to their physico-chemical properties, which have opened up new and interesting opportunities in a wide range of biomedical applications, such as wound healing. It is worth noting that GO and rGO may offer a convenient access to its ready dispersion within various polymeric matrices (such as cellulose and its derivative forms), owing to their large surface area, based on a carbon skeleton with many functional groups (i.e., hydroxyl, carboxyl, epoxy bridge, and carbonyl moieties). This results in new synergic properties due to the presence of both components (GO or rGO and polymers), acting at different length-scales. Furthermore, they have shown efficient antimicrobial and angiogenic properties, mostly related to the intracellular formation of reactive oxygen species (ROS), which are advantageous in wound care management. For this reason, GO or rGO integration in cellulose-based matrixes have allowed for designing highly advanced multifunctional hybrid nanocomposites with tailored properties. The current review aims to discuss a potential relationship between structural and physico-chemical properties (i.e., size, edge density, surface chemistry, hydrophilicity) of the nanocomposites with antimicrobials and angiogenic mechanisms that synergically influence the wound healing phenomenon, by paying particular attention to recent findings of GO or rGO/cellulose nanocomposites. Accordingly, after providing a general overview of cellulose and its derivatives, the production methods used for GO and rGO synthesis, the mechanisms that guide antimicrobial and angiogenic processes of tissue repair, as well as the most recent and remarkable outcomes on GO/cellulose scaffolds in wound healing applications, will be presented.

Purification and biochemical characterization of two laccase isoenzymes isolated from Trichoderma harzianum S7113 and its application for bisphenol A degradation

Two laccase isoenzymes (LacA and LacB) were isolated from a novel Trichoderma harzianum S7113 isolate employing ammonium sulfate precipitation, Sephadex G100, and DEAE Sepharose ion exchange chromatography. The molecular weights of the purified LacA and LacB laccases were estimated to be 63 and 48 kDa, respectively. The two isoenzymes had their optimum activities at the same temperature (50 °C), but at slightly different pH values (pH 3.0 for LacA and pH 2.5 for LacB). LacA and LacB had the same thermal stability at 40 °C and pH stability at pH 9.0. The two isoenzymes also showed a high level of specific activity toward ABTS, where the K_m values of LacA and LacB were 0.100 and 0.065 mM, whereas their V_max values were 0.603 and 0.182 µmol min^-1, respectively. LacA and LacB catalytic activity was stimulated by Mg²⁺, Zn²⁺, K⁺, and Ni²⁺, whereas it was inhibited by Hg²⁺ and Pb²⁺, β-mercaptoethanol, EDTA, and SDS, and completely inhibited by sodium azide. Our findings indicate that purified laccase has a promising capacity for bisphenol A (BPA) bioremediation across a broad pH range. This finding opens up new opportunities for the commercialization of this technique in a variety of biotechnology-based applications, particularly for removing endocrine chemicals from the environment.

Enzymes and enzymatic mechanisms in enzymatic degradation of lignocellulosic biomass: A mini-review

Enzymatic hydrolysis is the key step limiting the efficiency of the biorefinery of lignocellulosic biomass. Enzymes involved in enzymatic hydrolysis and their interactions with biomass should be comprehended to form the basis for looking for strategies to improve process efficiency. This article updates the contemporary research on the properties of key enzymes in the lignocellulose biorefinery and their interactions with biomass, adsorption, and hydrolysis. The advanced analytical techniques to track the interactions for exploiting mechanisms are discussed. The challenges and prospects for future research are outlined.

Environmental and Human Health Impact of Disposable Face Masks During the COVID-19 Pandemic: Wood-Feeding Termites as a Model for Plastic Biodegradation

The ongoing COVID-19 pandemic has resulted in an unprecedented form of plastic pollution: personal protective equipment (PPE). On the eve of the COVID-19 pandemic, there is a tremendous increase in the production of plastic-based PPE. To control the spread of the virus, face masks (FMs) are used as primary PPE. Thus, the production and usage of FM significantly increased as the COVID-19 pandemic was still escalating. The primary raw materials for the manufacturing of FMs are non-biodegradable synthetic polymers derived from petrochemicals. This calls for an urgent need to develop novel strategies for the efficient degradation of plastics. Furthermore, most of these masks contain plastic or other derivatives of plastic. The extensive usage of FM generates millions of tons of plastic waste for the environment in a short span of time. However, their degradation in the environment and consequences are poorly understood. Therefore, the potential impacts of disposable FM on the environment and human health during the COVID-19 pandemic are clarified in the present study. Despite structural and recalcitrance variations, lignocellulose and plastic polymers have physicochemical features, including carbon skeletons with comparable chemical bonds as well as hydrophobic properties in amorphous and crystalline regions. In this review, we argue that there is much to be learned from termites by transferring knowledge from research on lignocellulose degradation by termites to that on plastic waste.

Transcriptome Analysis of Podoscypha petalodes Strain GGF6 Reveals the Diversity of Proteins Involved in Lignocellulose Degradation and Ligninolytic Function

The present study reports transcriptomic profiling of a Basidiomycota fungus, Podoscypha petalodes strain GGF6 belonging to the family Podoscyphaceae, isolated from the North-Western Himalayan ranges in Himachal Pradesh, India. Podoscypha petalodes strain GGF6 possesses significant biotechnological potential as it has been reported for endocellulase, laccase, and other lignocellulolytic enzymes under submerged fermentation conditions. The present study attempts to enhance our knowledge of its lignocellulolytic potential as no previous omics-based analysis is available for this white-rot fungus. The transcriptomic analysis of P. petalodes GGF6 reveals the presence of 280 CAZy proteins. Furthermore, bioprospecting transcriptome signatures in the fungi revealed a diverse array of proteins associated with cellulose, hemicellulose, pectin, and lignin degradation. Interestingly, two copper-dependent lytic polysaccharide monooxygenases (AA14) and one pyrroloquinolinequinone-dependent oxidoreductase (AA12) were also identified, which are known to help in the lignocellulosic plant biomass degradation. Overall, this transcriptome profiling-based study provides deeper molecular-level insights into this Basidiomycota fungi, P. petalodes, for its potential application in diverse biotechnological applications, not only in the biofuel industry but also in the environmental biodegradation of recalcitrant molecules.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-022-01037-6.

Ligninolytic characteristics of Pleurotus ostreatus cultivated in cotton stalk media

Biodelignification is widely regarded as a low-efficiency process because it is usually slow and difficult to control. To improve its efficiency and understand its mechanism, the present study analyzed the delignification characteristics of Pleurotus ostreatus grown on a cotton stalk medium. The results demonstrated that all strains of P. ostreatus can selectively degrade the cotton stalk lignin. When cultured in a cotton stalk medium for 60 days, P. ostreatus degraded lignin primarily during its mycelium growth with up to 54.04% lignin degradation and produced laccase and manganese dependent peroxidase with high activity levels at the peaks of 70.17 U/ml and 62.39 U/ml, respectively, but no detectable lignin peroxidase. The results of nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy analyses of significant changes in lignin structure revealed that syringyl (S) lignin units were more degraded than guaiacyl (G) lignin units, with a significantly elevated G/S ratio. The Gas Chromatography-Mass Spectrometer analysis of low-molecular-weight compounds revealed that the delignification resulted in the formation of alcohols, organic acids, benzodiazepines, and alkanes. Identified benzodiazepines implied the degradation of G and S units of lignin. These findings will help to improve the efficiency of biodelignification and expand our understanding of its mechanism.

Functional Characterization of Laccase Isozyme (PoLcc1) from the Edible Mushroom Pleurotus ostreatus Involved in Lignin Degradation in Cotton Straw

Fungal laccases play important roles in the degradation of lignocellulose. In this study, the laccase producing cotton straw medium for Pleurotus ostreatus was optimized by single-factor and orthogonal experiments, and to investigate the role of Lacc1 gene, one of the laccase-encoding genes, in the degradation of cotton straw lignin, an overexpression strain of Lacc1 gene was constructed, which was analyzed for the characteristics of lignin degradation. The results demonstrated that the culture conditions with the highest lignin degradation efficiency of the P. ostreatus were the cotton straw particle size of 0.75 mm, a solid–liquid ratio of 1:3 and containing 0.25 g/L of Tween in the medium, as well as an incubation temperature of 26 °C. Two overexpression strains (OE L1-1 and OE L1-4) of Lacc1 gene were obtained, and the gene expression increased 12.08- and 33.04-fold, respectively. The results of ¹H-NMR and FTIR analyses of significant changes in lignin structure revealed that Lacc1 gene accelerated the degradation of lignin G-units and involved in the cleavage of β-O-4 linkages and the demethylation of lignin units. These findings will help to improve the efficiency of biodelignification and expand our understanding of its mechanism.

Valorisation Potential of Invasive Acacia dealbata, A. longifolia and A. melanoxylon from Land Clearings

Acacia spp. are invasive in Southern Europe, and their high propagation rates produce excessive biomass, exacerbating wildfire risk. However, lignocellulosic biomass from Acacia spp. may be utilised for diverse biorefinery applications. In this study, attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR), high-performance anion-exchange chromatography pulsed amperometric detection (HPAEC-PAD) and lignin content determinations were used for a comparative compositional characterisation of A. dealbata, A. longifolia and A. melanoxylon. Additionally, biomass was treated with three white-rot fungi species (Ganoderma lucidum, Pleurotus ostreatus and Trametes versicolor), which preferentially degrade lignin. Our results showed that the pre-treatments do not significantly alter neutral sugar composition while reducing lignin content. Sugar release from enzymatic saccharification was enhanced, in some cases possibly due to a synergy between white-rot fungi and mild alkali pretreatments. For example, in A. dealbata stems treated with alkali and P. ostreatus, saccharification yield was 702.3 nmol mg^-1, which is higher than the samples treated only with alkali (608.1 nmol mg^-1), and 2.9-fold higher than the non-pretreated controls (243.9 nmol mg^-1). By characterising biomass and pretreatments, generated data creates value for unused biomass resources, contributing to the implementation of sustainable biorefining systems. In due course, the generated value will lead to economic incentives for landowners to cut back invasive Acacia spp. more frequently, thus reducing excess biomass, which exacerbates wildfire risk.

Inhibitor formation and detoxification during lignocellulose biorefinery: A review

For lignocellulose biorefinery, pretreatment is needed to maximize the cellulose accessibility, frequently generating excess inhibitory substances to decline the efficiency of the subsequent fermentation processes. This mini-review updates the current research efforts to detoxify the adverse impacts of generated inhibitors on the performance of biomass biorefinery. The lignocellulose pretreatment processes are first reviewed. The generation of inhibitors, furans, furfural, phenols, formic acid, and acetic acid, from the lignocellulose, with their action mechanisms, are listed. Then the detoxification processes are reviewed, from which the biological detoxification processes are noted as promising and worth further study. The challenges and prospects for applying biological detoxification in lignocellulose biorefinery are outlined. Integrated studies considering the entire biorefinery should be performed on a case-by-case basis.

Agro-industrial wastes revalorization as feedstock: production of lignin-modifying enzymes extracts by solid-state fermentation using white rot fungi

The purpose of the study was to evaluate the production of lignin-modifying enzyme extracts and delignified biomass from agro-industrial wastes using white rot fungi (Inonotus sp. Sp2, Stereum hirsutum Ru-104, Bjerkandera sp. BOS55, Pleurotus eryngii IJFM 169 and Phanerochaete chrysosporium BKM-F-1767). These were screened based on their adaptability and colonization ability on different substrates, as well as by the Laccase, Manganese peroxidase, and Lignin peroxidase enzymatic production. Native strains (Inonotus sp. Sp2 and S. hirsutum Ru-104) showed the highest growth kinetics under the solid-substrate fermentation conditions and the growth rate parameters of the kinetic logistic model for the different substrates were between 0.39-0.81 (1/d) and 0.42-0.83 (1/d), respectively; the determination coefficients were ≥0.99. Inonotus sp. Sp2 was subsequently cultured in static flasks to produce crude enzyme extracts, obtaining manganese peroxidase activity levels of 18.5 and 31.3 (U/g) when growing in corn cob husk and spent tea leaves, respectively. Besides, it was to establish that the best conditions for lignin-modifying enzymes production using corn cob husk are 70% of initial moisture and 2.12 mm of particle size; reaching after 30 incubation days a manganese peroxidase activity of 21 ± 6 (U/g) under these conditions; enzyme that showed a suitable thermostability.

Whole-genome sequence of a high-temperature edible mushroom Pleurotus giganteus (zhudugu)

Most of the sequenced wood-rotting edible mushroom produce fruiting body at relatively low temperatures. Little information has been known about the high-temperature wood-rotting mushroom. Here, we performed de novo sequencing and assembly of the genome of a high-temperature edible mushroom Pleurotus giganteus from a monokaryotic strain zhudugu2 using the Illumina and Pac-Bio CLR sequencing technologies. P. giganteus, also known as Zhudugu in China, is a well-known culinary edible mushroom that has been widely distributed and cultivated in China, Southeast Asia, and South Asia. The genome consists of 40.00 Mb in 27 contigs with a contig N50 of 4.384 Mb. Phylogenetic analysis reveals that P. giganteus and other strains in Pleurotus clustered in one clade. Phylogenetic analysis and average nucleotide identity analysis indicated that the P. giganteus genome showed a closer relationship with other Pleurotus species. Chromosome collinearity analysis revealed a high level of collinearity between P. ostreatus and P. giganteus. There are 12,628 protein-coding genes annotated in this monoploid genome. A total of 481 enzymes accounting for 514 carbohydrate-active enzymes (CAZymes) terms were identified in the P. giganteus genome, including 15 laccases and 10 class II peroxidases predicted in the genome, which revealed the robustness of lignocellulose degradation capacity of P. giganteus. The mating-A type locus of P. giganteus consisted of a pair of homeodomain mating-type genes HD1 and HD2. The mating-B type locus of P. giganteus consisted of at least four pheromone receptor genes and three pheromone genes. The genome is not only beneficial for the genome-assisted breeding of this mushroom but also helps us to understand the high-temperature tolerance of the edible mushroom.

Role of ascomycete and basidiomycete fungi in meeting established and emerging sustainability opportunities: a review

Fungal biomass is the future's feedstock. Non-septate Ascomycetes and septate Basidiomycetes, famously known as mushrooms, are sources of fungal biomass. Fungal biomass, which on averagely comprises about 34% protein and 45% carbohydrate, can be cultivated in bioreactors to produce affordable, safe, nontoxic, and consistent biomass quality. Fungal-based technologies are seen as attractive, safer alternatives, either substituting or complementing the existing standard technology. Water and wastewater treatment, food and feed, green technology, innovative designs in buildings, enzyme technology, potential health benefits, and wealth production are the key sectors that successfully reported high-efficiency performances of fungal applications. This paper reviews the latest technical know-how, methods, and performance of fungal adaptation in those sectors. Excellent performance was reported indicating high potential for fungi utilization, particularly in the sectors, yet to be utilized and improved on the existing fungal-based applications. The expansion of fungal biomass in the industrial-scale application for the sustainability of earth and human well-being is in line with the United Nations' Sustainable Development Goals.

Biological depolymerization of lignin using laccase harvested from the autochthonous fungus Schizophyllum commune employing various production methods and its efficacy in augmenting in vitro digestibility in ruminants

A laccase-producing hyper performer, Schizophyllum commune, a white-rot fungus, was evaluated for its ability to selectively degrade lignin of diverse crop residues in vitro. Relative analysis of crop residue treatment using laccase obtained from immobilized cells demonstrated degradation of 30–40% in finger millet straw and sorghum stover, 27–32% in paddy straw, 21% in wheat straw, and 26% in maize straw, while 20% lignin degradation was observed when purified and recombinant laccase was used. Further investigations into in vitro dry matter digestibility studies gave promising results recording digestibility of 54–59% in finger millet straw 33–36% in paddy straw and wheat straw, 16% in maize straw for laccase obtained from cell immobilization method, whereas 14% digestibility was observed when purified and recombinant laccase was used. Sorghum stover recorded digestibility of 13–15% across all straws treated with laccase. The results obtained elucidated the positive influence of laccase treatment on lignin degradation and in vitro dry matter digestibility. The present research gave encouraging figures confirming the production of laccase using the cell immobilization method to be an efficient production method commensurate with purified and recombinant laccase under conditions of submerged cultivation, proclaiming a cost-effective, environmentally safe green technology for effectual lignin depolymerization.

Use of Anthracophyllum Discolor and Stereum Hirsutum as a Suitable Strategy for Delignification and Phenolic Removal of Olive Mill Solid Waste

This study evaluated the use of the white-rot fungi (WRF) Anthracophyllum discolor and Stereum hirsutum as a biological pretreatment for olive mill solid mill waste (OMSW). The WRF strains proposed were added directly to OMSW. The assays consisted of determining the need to add supplementary nutrients, an exogenous carbon source or use agitation systems, and evaluating WRF growth, enzyme activity, phenolic compound removal and lignin degradation. The highest ligninolytic enzyme activity was found at day 10, reaching 176.7 U/L of manganese-independent peroxidase (MniP) produced by A. discolor, and the highest phenolic removal (more than 80% with both strains) was reached after 24 days of incubation. The confocal laser scanning microscopy analysis (CLSM) confirmed lignin degradation through the drop in lignin relative fluorescence units (RFU) from 3967 for untreated OMSW to 235 and 221 RFU, showing a lignin relative degradation of 94.1% and 94.4% after 24 days of treatment by A. discolor and S. hirsutum, respectively. The results demonstrate for the first time that A. discolor and S. hirsutum were able to degrade lignin and remove phenolic compounds from OMSW using this as the sole substrate without adding other nutrients or using agitation systems. This work indicates that it could be possible to design an in situ pretreatment of the valorization of OMSW, avoiding complex systems or transportation. In this sense, future research under non-sterile conditions is needed to evaluate the competition of WRF with other microorganisms present in the OMSW. The main drawbacks of this work are associated with both the low reaction time and the water addition. However, OMSW is seasonal waste produced in one season per year, being stored for a long time. In terms of water addition, the necessary optimization will be addressed in future research.