The white-rot fungus Phanerochaete chrysosporium: conditions for the production of lignin-degrading enzymes

Metabolomics analysis of advancing humification mechanism in secondary fermentation of composting by fungal bioaugmentation

The aim of this study was to investigate the differential metabolites and core metabolic pathways caused by fungal bioaugmentation (pH regulation and Phanerochaete chrysosporium inoculation) in secondary fermentation of composting, as well as their roles in advancing humification mechanism. Metabolomics analyses showed that inoculation strengthened the expression of carbohydrate, amino acid, and aromatic metabolites, and pH regulation resulted in the up-regulation of the phosphotransferase system and its downstream carbohydrate metabolic pathways, inhibiting Toluene degradation and driving biosynthesis of aromatic amino acids via the Shikimate pathway. Partial least squares path model suggested that lignocellulose degradation, precursors especially amino acids and their metabolism process enhanced by the regulation of pH and Phanerochaete were the main direct factors for humic acid formation in composting. This finding helps to understand the regulating mechanism of fungal bioaugmentation to improve the maturity of agricultural waste composting.

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.

Effect of alkali treatment on enzymatic hydrolysis of p-toluenesulfonic acid pretreated bamboo substrates

The comprehensive separation and utilization of whole components of lignocellulosic materials has received extensive attention in present research. This study focused on the efficacy of alkali treatment for enzymatic saccharification of cellulose based on p-toluenesulfonic acid (p-TsOH) pretreated bamboo substrate. The results showed that the cellulose to glucose conversion yield was 94.69 % under optimized conditions of 0.4 g NaOH/g, 160 °C and 4 h (soaked), which after only 6 h enzymatic hydrolysis time. Alkali lignin recovery was 88.51 %, with potential for conversion to lignin derivatives. The yield of hemicellulose in the pretreated filtrate was 51.85 % after the 4th cycling reuse of p-TsOH. This work has borrowed the advantages of p-TsOH pretreatment of depolymerized hemicellulose from bamboo, combined with a low-priced weak alkali secondary treatment method, which can be effectively applied to the co-production of lignin, xylooligosaccharide, xylose and glucose, and the whole process is green and economically sustainable.

Enhancing biogas generation from lignocellulosic biomass through biological pretreatment: Exploring the role of ruminant microbes and anaerobic fungi

Biogas production from Lignocellulosic Biomass (LB) via anaerobic digestion (AD) has gained attention for its potential in self-sustainability. However, the recalcitrance of LB cell walls pose a challenge to its degradability and biogas generation. Therefore, pretreatment of LB is necessary to enhance lignin removal and increase degradability. Among the different approaches, environmentally friendly biological pretreatment ispromising as it avoids the production of inhibitors. The ruminal microbial community, including anaerobic fungi, bacteria, and protozoa, has shown an ability to effectively degrade LB through biomechanical and microbial penetration of refractory cell structures. In this review, we provide an overview of ruminant microbes dominating LB's AD, their degradation mechanism, and the bioaugmentation of the rumen. We also explore the potential cultivation of anaerobic fungi from the rumen, their enzyme potential, and their role in AD. The rumen ecosystem, comprising both bacteria and fungi, plays a crucial role in enhancing AD. This comprehensive review delves into the intricacies of ruminant microorganisms' adhesion to plant cells, elucidates degradation mechanisms, and explores integrated pretreatment approaches for the effective utilization of LB, minimizing the impact of inhibitors. The discussion underscores the considerable potential of ruminant microbes in pretreating LB, paving the way for sustainable biogas production. Optimizing fungal colonization and ligninolytic enzyme production, such as manganese peroxidase and laccase, significantly enhances the efficiency of fungal pretreatment. Integrating anaerobic fungi through bioaugmentation during mainstream processing demonstrably increases methane production. This study opens promising avenues for further research and development of these microorganisms for bioenergy production.

Synergistic lignin degradation between Phanerochaete chrysosporium and Fenton chemistry is mediated through iron cycling and ligninolytic enzyme induction

Removal of recalcitrant lignin from wastewater remains a critical bottleneck in multiple aspects relating to microbial carbon cycling ranging from incomplete treatment of biosolids during wastewater treatment to limited conversion of biomass feedstock to biofuels. Based on previous studies showing that the white rot fungus Phanerochaete chrysosporium and Fenton chemistry synergistically degrade lignin, we sought to determine optimum levels of Fenton addition and the mechanisms underlying this synergy. We tested the extent of degradation of lignin under different ratios of Fenton reagents and found that relatively low levels of H2O2 and Fe(II) enhanced fungal lignin degradation, achieving 80.4 ± 1.61 % lignin degradation at 1.5 mM H2O2 and 0.3 mM Fe(II). Using a combination of whole-transcriptome sequencing and iron speciation assays, we determined that at these concentrations, Fenton chemistry induced the upregulation of 80 differentially expressed genes in P. ch including several oxidative enzymes. This study underlines the importance of non-canonical, auxiliary lignin-degrading pathways in the synergy between white rot fungi and Fenton chemistry in lignin degradation. We also found that, relative to the abiotic control, P. ch. increases the availability of Fe(II) for the production of hydroxyl radicals in the Fenton reaction by recycling Fe(III) (p < 0.001), decreasing the Fe(II) inputs necessary for lignin degradation via the Fenton reaction.

Elucidating the role of media nitrogen in augmenting the production of lignin-depolymerizing enzymes by white-rot fungi

Indigenous white-rot fungal isolates Schizophyllum commune, Phanerochaete chrysosporium, Ganoderma racenaceum, and Lentinus squarrosulus, demonstrating the ability to depolymerize lignin of the crop residues, were studied for their potential to produce ligninolytic enzymes using modified production media under conditions of limiting and excess nitrogen for higher enzymatic expressions. Secretome-rich media on the investigation confirmed the successful production of lignin-depolymerizing enzymes, viz. laccase, lignin peroxidase, manganese peroxidase, and versatile peroxidase. Production of laccases and peroxidases was statistically significant in nitrogen-limiting media with and without the substrate, across all white-rot fungal cultures at 95% confidence interval. Nitrogen-limiting media with the substrate on analysis extracellularly expressed 99.27 U of laccase and 68.48 U of manganese peroxidase in Schizophyllum commune, while 195.14 U of lignin peroxidase was produced by Phanerochaete chrysosporium. Lentinus squarrosulus expressed 455.34 U of laccase and 357.13 U of versatile peroxidase with 250.09 U of laccase and 206.95 U of manganese peroxidase produced by Ganoderma racenaceum for every milliliter of the media used. Nitrogen-limiting media triggered the production of laccase during the initial stages of growth while the expression of peroxidases was predominant at a later stage. Also, this media evinced increased enzymatic yields with low biomass content compared to nitrogen-excess conditions. The extant study confirmed the positive influence of nitrogen-limiting media in the efficient production of ligninolytic enzymes and their suggestive degradation potential for environmental pollutants, making these enzymes a safe, clean alternative to the use of chemicals and the media to be effective for large-scale production of ligninolytic enzymes. IMPORTANCE Lignin on account of its high abundance, complex polymeric structure, and biochemical properties is identified as a promising candidate in renewable energy and bioproduct manufacturing. However, depolymerization of lignin remains a major challenge in lignin utilization, entailing the employment of harsh treatments representing not only an environmental concern but also a waste of economic potential. Developing an alternative green technology to minimize this impact is imperative. Methods using enzymes to depolymerize lignin are the focus of recent studies. Current research work emphasized the efficient expression of the major lignin-depolymerizing enzymes: laccases, lignin peroxidases, manganese peroxidases, and versatile peroxidases from native isolates of white-rot fungus for several biotechnological applications as well as treatment of crop residues for use as ruminant feed in improving productivity. The importance of nitrogen in augmenting the expression of lignin-depolymerizing enzymes and providing a media recipe for the cost-effective production of ligninolytic enzymes is highlighted.

Effects of Solid-State Fermentation Pretreatment with Single or Dual Culture White Rot Fungi on White Tea Residue Nutrients and In Vitro Rumen Fermentation Parameters

Fermentation of agricultural by-products by white rot fungi is a research hotspot in the development of ruminant feed resources. The aim of this study was to investigate the potential of the nutritional value and rumen fermentation properties of white tea residue fermented at different times, using single and dual culture white rot fungal species. Phanerochaete chrysosporium, Pleurotus ostreatus, and Phanerochaete chrysosporium + Pleurotus ostreatus (dual culture) solid-state fermented white tea residue was used for 4 weeks, respectively. The crude protein content increased significantly in all treatment groups after 4 weeks. Total extractable tannin content was significantly decreased in all treatment groups (p < 0.01). P. chrysosporium and dual culture significantly reduced lignin content at 1 week. The content of NH3-N increased in each treatment group (p < 0.05). P. chrysosporium treatment can reduce the ratio of acetic to propionic and improve digestibility. Solid state fermentation of white tea residue for 1 week using P. chrysosporium was the most desirable.

Biodelignification of lignocellulose using ligninolytic enzymes from white-rot fungi

Lignocellulose is the most abundant biomass available on earth, including wood and agricultural wastes such as rice straw, corn cobs, and oil palm empty bunches. The biopolymer content in lignocellulose has a great potential as feedstock for producing industrial raw materials such as glucose, sorbitol, xylose, xylitol, and other pharmaceutical excipients. Currently, scientists and governments agree that the enzymatic delignification method is an environmentally friendly green method to be applied. This review attempts to explain the proper preparation of the enzymes laccase, lignin peroxidase, and manganese peroxidase, as well as the important factors influencing their activity. The recent applications of the enzymes for detoxification of hazardous substances, proper enzyme immobilization technique, and future prospect combination with DESs extraction of lignin are also discussed.

Bioremoval and tolerance study of sulfamethoxazole using whole cell Trichoderma harzianum isolated from rotten tree bark

Antibiotic contamination raises concerns over antibiotic resistance genes (ARGs), which can severely impact the human health and environment. Sulfamethoxazole (SMX) is a widely used antibiotic that is incompletely metabolized in the body. In this study, the research objectives were (1) to isolate the native strain of Trichoderma sp. from the environment and analyze the tolerance toward SMX concentration by evaluating fungal growth, and (2) to investigate the potential of SMX removal by fungi. The potential fungi isolated from rotten tree bark showed 97% similarity to Trichoderma harzianum (Accession no. MH707098.1). The whole cell of fungi was examined in vitro; the strain Trichoderma harzianum BGP115 eliminated 71% of SMX after 7 days, while the white rot fungi Trametes versicolor, demonstrated 90% removal after 10 days. Furthermore, the tolerance of fungal growth toward SMX concentration at 10 mg L^-1 was analyzed, which indicated that Trichoderma harzianum BGP115 (the screened strain) exhibited more tolerance toward SMX than Trametes versicolor (the reference strain). The screened fungi isolated from rotted tree bark demonstrated the ability of SMX bioremoval and the potential to be tolerant to high concentrations of SMX.

A comprehensive insight into the application of white rot fungi and their lignocellulolytic enzymes in the removal of organic pollutants

Environmental problems resultant from organic pollutants are a major current challenge for modern societies. White rot fungi (WRF) are well known for their extensive organic compound degradation abilities. The unique oxidative and extracellular ligninolytic systems of WRF that exhibit low substrate specificity, enable them to display a considerable ability to transform or degrade different environmental contaminants. In recent decades, WRF and their ligninolytic enzymes have been widely applied in the removal of polycyclic aromatic hydrocarbons (PAHs), pharmaceutically active compounds (PhACs), endocrine disruptor compounds (EDCs), pesticides, synthetic dyes, and other environmental pollutants, wherein promising results have been achieved. This review focuses on advances in WRF-based bioremediation of organic pollutants over the last 10 years. We comprehensively document the application of WRF and their lignocellulolytic enzymes for removing organic pollutants. Moreover, potential problems and intriguing observations that are worthy of additional research attention are highlighted. Lastly, we discuss trends in WRF-remediation system development and avenues that should be considered to advance research in the field.

A Review on the Utilization of Lignin as a Fermentation Substrate to Produce Lignin-Modifying Enzymes and Other Value-Added Products

The lignocellulosic biomass is comprised of three major components: cellulose, hemicellulose, and lignin. Among these three, cellulose and hemicellulose were already used for the generation of simple sugars and subsequent value-added products. However, lignin is the least applied material in this regard because of its complex and highly variable nature. Regardless, lignin is the most abundant material, and it can be used to produce value-added products such as lignin-modifying enzymes (LMEs), polyhydroxyalkanoates (PHAs), microbial lipids, vanillin, muconic acid, and many others. This review explores the potential of lignin as the microbial substrate to produce such products. A special focus was given to the different types of lignin and how each one can be used in different microbial and biochemical pathways to produce intermediate products, which can then be used as the value-added products or base to make other products. This review paper will summarize the effectiveness of lignin as a microbial substrate to produce value-added products through microbial fermentations. First, basic structures of lignin along with its types and chemistry are discussed. The subsequent sections highlight LMEs and how such enzymes can enhance the value of lignin by microbial degradation. A major focus was also given to the value-added products that can be produced from lignin.

Self-Sustaining Bioelectrochemical Cell from Fungal Degradation of Lignin-Rich Agrowaste

The present work describes a self-sustaining bioelectrochemical system that adopts simple cell configurations and operates in uncontrolled ambient surroundings. The microbial fuel cell (MFC) was comprised of white-rot fungus of Phanaerochaete chrysosporium fed with oil palm empty fruit bunch (EFB) as the substrate. This fungal strain degrades lignin by producing ligninolytic enzymes such as laccase, which demonstrates a specific affinity for oxygen as its electron acceptor. By simply pairing zinc and the air electrode in a membraneless, single-chamber, 250-mL enclosure, electricity could be harvested. The microbial zinc/air cell is capable of sustaining a 1 mA discharge current continuously for 44 days (i.e., discharge capacity of 1056 mAh). The role of the metabolic activities of P. chrysosporium on EFB towards the MFC’s performance is supported by linear sweep voltammetry measurement and scanning electron microscopy observations. The ability of the MFC to sustain its discharge for a prolonged duration despite the fungal microbes not being attached to the air electrode is attributed to the formation of a network of filamentous hyphae under the submerged culture. Further, gradual lignin decomposition by fungal inocula ensures a continuous supply of laccase enzyme and radical oxidants to the MFC. These factors promote a self-sustaining MFC devoid of any control features.

Fed-batch production of Thermothelomyces thermophilus lignin peroxidase using a recombinant Aspergillus nidulans strain in stirred-tank bioreactor

Enzymatic lignin depolymerization is considered a favorable approach to utilize lignin due to the higher selectivity and less energy requirement when compared to thermochemical lignin valorization. Lignin peroxidase (LiP) is one of the key enzymes involved in lignin degradation and possesses high redox potential to oxidize non-phenolic structures and phenolic compounds in lignin. However, the production of LiP is mainly from white-rot fungi at small scales. It is critical to discover new LiP from other microorganisms and produce LiP at large scales. This study aims to produce a novel LiP originally from Thermothelomyces thermophiles using a recombinant Aspergillus nidulans strain. The LiP production medium was optimized, and different fed-batch strategies for LiP production were investigated to improve LiP activity, yield, and productivity. Results demonstrated that LiP production was enhanced by using multi-pulse fed-batch fermentation. A maximum LiP activity of 1,645 mU/L with a protein concentration of 0.26 g/L was achieved.

Fungi in PAH-contaminated marine sediments: Cultivable diversity and tolerance capacity towards PAH

The cultivable fungal diversity from PAH-contaminated sediments was examined for the tolerance to polycyclic aromatic hydrocarbon (PAH). The 85 fungal strains, isolated in non-selective media, revealed a large diversity by ribosomal internal transcribed spacer (ITS) sequencing, even including possible new species. Most strains (64%) exhibited PAH-tolerance, indicating that sediments retain diverse cultivable PAH-tolerant fungi. The PAH-tolerance was linked neither to a specific taxon nor to the peroxidase genes (LiP, MnP and Lac). Examining the PAH-removal (degradation and/or sorption), Alternaria destruens F10.81 showed the best capacity with above 80% removal for phenanthrene, pyrene and fluoranthene, and around 65% for benzo[a]pyrene. A. destruens F10.81 internalized pyrene homogenously into the hyphae that contrasted with Fusarium pseudoygamai F5.76 in which PAH-vacuoles were observed but PAH removal was below 20%. Thus, our study paves the way for the exploitation of fungi in remediation strategies to mitigate the effect of PAH in coastal marine sediments.

The white-rot fungus, Phanerochaete chrysosporium, under combinatorial stress produces variable oil profiles following analysis of secondary metabolites

AIMS

The effects of combinatorial stress on lipid production in Phanerochaete chrysosporium remain understudied. This species of white-rot fungi was cultivated on solid-state media while under variable levels of known abiotic and biotic stressors to establish the effect upon fungal oil profiles.

METHODS AND RESULTS

Environmental stressors induced upon the fungus included the following: temperature, nutrient limitation and interspecies competition to assess impact upon oil profiles. Fatty acid type and its concentration were determined using analytical methods of gas chromatography and mass spectrometry. Growth rate under stress was established using high-performance liquid chromatography with ergosterol as the biomarker. Fungi grown on solid-state agar were able to simultaneously produce short- and long-chain fatty acids which appeared to be influenced by nutritional composition as well as temperature. Addition of nitrogen supplements increased the growth rate, but lipid dynamics remained unchanged. Introducing competition-induced stress had significantly altered the production of certain fatty acids beyond that of the monoculture while under nutrient-limiting conditions. Linoleic acid concentrations, for example, increased from an average of 885 ng μl^-1 at monoculture towards 13 820 ng μl^-1 at co-culture, following 7 days of incubation.

CONCLUSIONS

Interspecies competition produced the most notable impact on lipid production for solid-state media cultivated fungi while the addition of nitrogen supplementation presented growth and lipid accumulation to be uncorrelated. Combinatorial stress therefore influences the yield of overall lipid production as well as the number of intermediate fatty acids produced, deriving similar oil profiles to the composition of vegetable and fish oils.

SIGNIFICANCE AND IMPACT OF THE STUDY

Fungal secondary metabolism remains highly sensitive following combinatorial stress. The outcome impacts the research towards optimizing fungal oil profiles for biomass and nutrition. Future investigations on fungal stress tolerance mechanisms need to address these environmental factors throughout the experimental design.

Inhibition of Phenolics Uptake by Ligninolytic Fungal Cells and Its Potential as a Tool for the Production of Lignin-Derived Aromatic Building Blocks

Lignin is the principal natural source of phenolics but its structural complexity and variability make it difficult to valorize through chemical depolymerization approaches. White rots are one of the rare groups of organisms that are able to degrade lignin in ecosystems. This biodegradation starts through extracellular enzymes producing oxidizing agents to depolymerize lignin and continue with the uptake of the generated oligomers by fungal cells for further degradation. Phanerochaete chrysosporium is one of the most studied species for the elucidation of these biodegradation mechanisms. Although the extracellular depolymerization step appears interesting for phenolics production from lignin, the uptake and intracellular degradation of oligomers occurring in the course of the depolymerization limits its potential. In this study, we aimed at inhibiting the phenolics uptake mechanism through metabolic inhibitors to favor extracellular oligomers accumulation without preventing the ligninases production that is necessary for extracellular depolymerization. The use of sodium azide confirmed that an active transportation phenomenon is involved in the phenolics uptake in P. chrysosporium. A protocol based on carbonyl cyanide m-chlorophenyl hydrazone enabled reaching 85% inhibition for vanillin uptake. This protocol was shown not to inhibit, but on the contrary, to stimulate the depolymerization of both dehydrogenation polymers (DHPs) and industrial purified lignins.

Fungal Degradation of Wood: Emerging Data, New Insights and Changing Perceptions

Wood durability researchers have long described fungal decay of timber using the starkly simple terms of white, brown and soft rot, along with the less destructive mold and stain fungi. These terms have taken on an almost iconic meaning but are only based upon the outward appearance of the damaged timber. Long-term deterioration studies, as well as the emerging genetic tools, are showing the fallacy of simplifying the decay process into such broad groups. This paper briefly reviews the fundamentals of fungal decay, staining and mold processes, then uses these fundamentals as the basis for a discussion of fungal attack of wood in light of current knowledge about these processes. Biotechnological applications of decay fungi are reviewed, and an overview is presented on how fungi surmount the protective barriers that coatings provide on surfaces. Advances in biochemical analyses have, in some cases, radically altered our perceptions of how wood is degraded, and even the relationships between fungal species, while other new findings have reinforced traditional perspectives. Suggestions for future research needs in the coatings field relative to enhanced fungal and environmental protection are presented.

Quantitative comparison of the biomass-degrading enzyme repertoires of five filamentous fungi

The efficiency of microorganisms to degrade lignified plants is of great importance in the Earth's carbon cycle, but also in industrial biorefinery processes, such as for biofuel production. Here, we present a large-scale proteomics approach to investigate and compare the enzymatic response of five filamentous fungi when grown on five very different substrates: grass (sugarcane bagasse), hardwood (birch), softwood (spruce), cellulose and glucose. The five fungi included the ascomycetes Aspergillus terreus, Trichoderma reesei, Myceliophthora thermophila, Neurospora crassa and the white-rot basidiomycete Phanerochaete chrysosporium, all expressing a diverse repertoire of enzymes. In this study, we present comparable quantitative protein abundance values across five species and five diverse substrates. The results allow for direct comparison of fungal adaptation to the different substrates, give indications as to the substrate specificity of individual carbohydrate-active enzymes (CAZymes), and reveal proteins of unknown function that are co-expressed with CAZymes. Based on the results, we present a quantitative comparison of 34 lytic polysaccharide monooxygenases (LPMOs), which are crucial enzymes in biomass deconstruction.

Occurrence of methylisothiazolinone in water and soil samples in Poland and its biodegradation by Phanerochaete chrysosporium

Methylisothiazolinone is a commonly used biocide that is released into natural environments. In this work, the ability of the fungal strain Phanerochaete chrysosporium DSM 1556 to biotransform this compound was evaluated. The tested strain was able to remove MIT (at concentrations 50 μg L^-1 and 30 mg L^-1) from the growth medium with the efficiency 90% after the first 6 h and 100% after 12 h of incubation. Moreover, for the first time, qualitative LC-MS/MS and GC-MS analysis showed monohydroxylated and dihydroxylated methylisothiazolinone and N-methylmalonamic acid as the main products of fungal biodegradation. The ecological toxicity of the tested biocide and its derivatives was also evaluated by using an acute toxicity test with Daphnia magna. An approximately 90% decrease in the toxicity of metabolites formed in the P. chrysosporium culture was noticed. The concentration of MIT in soil and water samples collected in Poland was assessed for the first time. The analysis showed that the selected locations in Poland are contaminated by MIT in the range from 1.04-10.08 μg L^-1.

Advanced biological sequential treatment of mature landfill leachate using aerobic activated sludge SBR and fungal bioreactor

This study utilized Penicillium spp. to treat mature landfill leachate (MLL) in a continuous bioreactor and batch experimental tests under non-sterile conditions. MLL characteristics such as chemical oxygen demand (COD), soluble COD (sCOD), total carbon (TC), total organic carbon (TOC), and color removal efficiency were determined. The lignocellulosic enzymatic activity of laccase (Lac), lignin-peroxidase (LiP), and manganese-peroxidase (MnP) was also determined. The batch experimental test was carried out with raw and pretreated MLL containing the initial NH4 +-N concentrations of 0, 105, 352, and 914 mg/L. A maximum COD reduction of 41% and maximum enzymatic activity of 193, 37, and 25 U/L for Lac, LiP and MnP was recorded for the MLL containing 352 mg/L NH4 +-N. The continuous bioreactor exhibited maximum values of 52, 54, 60, 58, and 75 percentage of COD, sCOD, TC, TOC, and color removal efficiency with MLL containing 352 mg/L NH4 +-N that was pretreated at HRT 120 h, while the maximum detected lignocellulosic enzymatic activities were 149, 27, and 16 U/L for Lac, LiP, and MnP, respectively. A total of 64% COD reduction was achieved from the raw MLL considering 12% COD and 100% NH4 +-N reduction in the aerobic activated sludge sequencing batch reactor pretreatment process. The steady and higher removal efficiency of the bioreactor over the entire study period is promising for further exploration to enhance removal of refractory contaminants from the MLL.

Evolution of Microbial Composition and Enzymatic Activities during the Composting of Textile Waste

The production of stable and mature compost often depends on the performance of microbes and their enzymatic activity. Environmental and nutritional conditions influence the characteristics of microbial communities and, therefore, the dynamics of major metabolic activities. Using three waste mixtures (textile waste mixed with either green, paper, or cardboard waste), the maturity of the compost produced was assessed by following the physico-chemical parameters and enzymatic activities provided by the microorganisms that were identified using next-generation sequencing (NGS). Among the three mixtures used, it was found that the two best mixtures showed C/N ratios of 16.30 and 16.96, total nitrogen of 1.37 and 1.39%, cellulase activities of 50.62 and 52.67 Ug−1, acid phosphatase activities of 38.81 and 68.77 Ug−1, and alkaline phosphatase activities of 51.12 and 56.86 Ug−1. In addition, several lignocellulosic species, together with those that are able to solubilize phosphate, were identified. Among those known for cellulase and acid/alkaline phosphatase activities, bacteria belonging to the Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes phyla were shown. The presence of species belonging to the Ascomycota and Basidiomycota phyla of Fungi, which are known for their ability to produce cellulase and acid/alkaline phosphatases, was demonstrated. These findings provide a basis for the production of stable and mature compost based on textile waste.

Synergistic codon optimization and bioreactor cultivation toward enhanced secretion of fungal lignin peroxidase in Pichia pastoris: Enzymatic valorization of technical (industrial) lignins

Lignin peroxidase (LiP) is a well-recognized enzyme for its ability to oxidize lignins, but its commercial availability is limited, which hinders the biotechnological application of LiP-based bioprocesses in lignocellulose biorefineries. This study evaluated a combination strategy to improve the expression of LiP to promote its practical use. The strategy included optimization of the lipH8 gene of Phanerochaete chrysosporium according to the codon usage of Pichia pastoris, followed by fed-batch fermentation using a 14 L bioreactor (10 L working volume). The combination strategy achieved a maximum volumetric LiPH8 activity of 4480 U L^-1, protein concentration of 417 mg L^-1 and a specific activity of 10.7 U mg^-1, which was higher than previous reports. Biochemical characterization showed that the recombinant LiPH8 (rLiPH8) was optimum at pH 3.0, 25 ℃ and 0.4 mM H₂O₂. Using the optimized conditions, rLiPH8 was used to treat isolated technical lignins namely soda-anthraquinone (SAQ) lignin and steam explosion (S-E) lignin. High-performance gel permeation chromatography (HP-GPC) analysis showed that the molecular weight (Mw) of SAQ and S-E lignins were increased by 1.43-and 1.14-fold, respectively, after the enzymatic treatment. Thermogravimetric analysis (TGA) also showed that the thermal stability of the lignins was improved, indicating that the enzyme treatment of lignins with rLiPH8 resulted in lignin re-polymerization. As the first report on rLiPH8 production using P. pastoris, this study has shed light on the possible route for the enhancement of rLiPH8 production and its potential application for upgrading technical lignins.

Mycoremediation: Expunging environmental pollutants

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Mycoremediation of polycyclic aromatic hydrocarbons, challenges, and strategies to overcome.

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Role of the fungi in eradicating heavy metal contamination from the polluted sites.

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Mycoremediation of agricultural wastes including pesticides, herbicides, and cyanotoxins.

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Pharmaceutical wastes and strategies for its remediation using white-rot and ligninolytic fungus.

The ever-increasing population, rapid rate of urbanization, and industrialization are exacerbating the pollution-related problems. Soil and water pollution affect human health and the ecosystem. Thus, it is crucial to develop strategies to combat this ever-growing problem. Mycoremediation, employing fungi or its derivatives for remediation of environmental pollutants, is a comparatively cost-effective, eco-friendly, and effective method. It has advantages over other conventional and bioremediation methods. In this review, we have elucidated the harmful effects of common pollutants on public health and the environment. The role of several fungi in degrading these pollutants such as heavy metals, agricultural, pharmaceutical wastes, including polycyclic aromatic hydrocarbons, is enumerated. Future strategies to improve the rate and efficiency of mycoremediation are suggested. The manuscript describes the strategies which can be used as a future framework to address the global problem of pollution.

Ligninolytic behavior of the white-rot fungus Stereum ostrea under influence of culture conditions, inducers and chlorpyrifos

The production of three ligninolytic enzymes, laccase (LAC), manganese peroxidase (MnP) and lignin peroxidase (LiP) by the white-rot fungus, Stereum ostrea, was significantly more in Koroljova liquid medium in the presence of chlorpyrifos under shaking conditions than under stationary conditions. These enzymes were secreted into the broth to the extent of 214.37, 82.75 and 8.05 U/ml under influence of chlorpyrifos on 10th day of incubation in comparison with 138.06, 51.85 and 6.44 U/ml, respectively, under similar conditions in control. Maximum production of LAC, MnP and LiP on liquid medium with/without chlorpyrifos under stationary conditions did not exceed 80-85, 33-40, 0.6-0.7 U/ml, respectively. Among lignosulfonic acid, veratryl alcohol (VA), gallic acid (GA) and tannic acid tested, GA induced maximum production of LAC (300.53 U/ml) and MnP (181.66 U/ml) after 10 days of growth in the presence of chlorpyriphos, while maximum LiP (1.134 U/ml) was produced when grown with the inducer VA during this period. Our data suggest that chlorpyrifos and inducers interacted positively in producing higher amounts of the ligninolytic enzymes in S. ostrea.

Bacterial Valorization of Lignin: Strains, Enzymes, Conversion Pathways, Biosensors, and Perspectives

Lignin, an aromatic polymer found in plants, has been studied for years in many biological fields. Initially, when biofuel was produced from lignocellulosic biomass, lignin was regarded as waste generated by the biorefinery and had to be removed, because of its inhibitory effects on fermentative bacteria. Although it has since proven to be a natural resource for bio-products with considerable potential, its utilization is confined by its complex structure. Hence, the microbial degradation of lignin has attracted researchers' interest to overcome this problem. From this perspective, the studies have primarily focused on fungal systems, such as extracellular peroxidase and laccase from white- and brown-rot fungi. However, recent reports have suggested that bacteria play an increasing role in breaking down lignin. This paper, therefore, reviews the role of bacteria in lignin and lignin-related research. Several reports on bacterial species in soil that can degrade lignin and their enzymes are included. In addition, a cellulolytic anaerobic bacterium capable of solubilizing lignin and carbohydrate simultaneously has recently been identified, even though the enzyme involved has not been discovered yet. The assimilation of lignin-derived small molecules and their conversion to renewable chemicals by bacteria, such as muconic acid and polyhydroxyalkanoates, including genetic modification to enhance their capability was discussed. This review also covers the indirect use of bacteria for lignin degradation, which is concerned with whole-cell biosensors designed to detect the aromatic chemicals released from lignin transformation.

Iron-rich microorganism-enabled synthesis of magnetic biocarbon for efficient adsorption of diclofenac from aqueous solution

Microorganisms in nature have been suggested as effective synthetic platform for functional materials construction. In this study, we cultured a typical white rot fungus of Phanerochaete chrysosporium in iron-containing medium to obtain iron-rich biomass, serving as sole precursor for magnetic biocarbon synthesis. The accumulated iron in biomass reached to 4.6 wt%. After carbonization and activation, microporous magnetic biocarbon (Fe/BC) with high specific surface area of 1986 m² g^-1 was obtained. When applied as adsorbent for a model pharmaceutical (diclofenac sodium, DCF) removal from aqueous solution, a high adsorption capacity of 361.25 mg g^-1 was found for the developed Fe/BC. Systematic isotherm, kinetic, thermodynamic and recycle studies were conducted to investigate adsorption behaviors of DCF onto Fe/BC. This work not only provides a novel strategy for magnetic biocarbon construction, but also envisions new perspective on the utilization of a variety of microorganisms in nature for functional materials preparation.

Recovery of glucose from dried distiller’s grain with solubles, using combinations of solid-state fermentation and insect culture

A bioethanol by-product, dried distiller’s grains with solubles (DDGS) contains high levels of cellulose and starch. We hypothesized that combinations of solid-state fermentation (SSF) and digestion by black soldier fly larvae (BSFL) (Hermetia illucens) could increase the recovery of glucose from this by-product by concentrating and loosening the cellulose matrix through their activities. DDGS was individually fermented with Aspergillus niger, Aspergillus fumigatus, Trichoderma koningii, Phanerochaete chrysosporium, or Lactobacillus plantarum. The fermented DDGS was fed to BSFL, and glucose recoveries from spent feeds were conducted. SSF increases lipid and protein contents, supporting BSFL growth, and weakens the cellulosic matrix. BSFL use nutrients in SSF–DDGS, further concentrating and weakening the cellulose, i.e., DDGS is halved without changing the cellulose contents. For example, Lactobacillus plantarum SSF with BSFL culture concentrates the cellulose content from 9.7% to 26.5% of spent feed. Glucose recovery was determined using three sequential processes (free glucose determination, weak-acid hydrolysis of amorphous cellulose, and enzymatic hydrolysis of micronized crystalline cellulose). Total glucose obtained from 100 g of DDGS increased from 4.8 to 10.7 g. These results show that the combinations of SSF and BSFL could provide additional fermentable sugars (and insect biomass) from bioethanol by-products, suggesting a high productivity from the same feedstock.

Decolorization of remazol brilliant blue R with laccase from Lentinus crinitus grown in agro-industrial by-products

Lentinus crinitus is a white-rot fungus that produces laccase, an enzyme used for dye decolorization. Enzyme production depends on cultivation conditions, mainly agro-industrial by-products. We aimed to produce laccase from Lentinus crinitus with agro-industrial by-products for dye decolorization. Culture medium had coffee husk (CH) or citric pulp pellet (CP) and different nitrogen sources (urea, yeast extract, ammonium sulfate and sodium nitrate) at concentrations of 0, 0.7, 1.4, 2.8, 5.6 and 11.2 g/L. Enzymatic extract was used in the decolorization of remazol brilliant blue R. CH medium promoted greater laccase production than CP in all evaluated conditions. Urea provided the greatest laccase production for CH (37280 U/L) as well as for CP (34107 U/L). In CH medium, laccase activity was suppressed when carbon-to-nitrogen ratio changed from 4.5 to 1.56, but the other nitrogen concentrations did not affect laccase activity. For CP medium, reduction in carbon-to-nitrogen ratio from 6 to 1.76 increased laccase activity in 17%. The peak of laccase activity in CH medium occurred on the 11th day (41246 U/L) and in CP medium on the 12th day (32660 U/L). The maximum decolorization within 24 h was observed with CP enzymatic extract (74%) and with CH extract (76%).

Evaluation of the Effects of Isolated Lignin on Cellulose Enzymatic Hydrolysis of Corn Stover Pretreatment by NaOH Combined with Ozone

In this experiment, corn stover was treated with optimal combined pretreatment conditions: 2% NaOH at 80 °C treated 2 h combined with initial pH 9 at the ozone concentration of 78 mg/mL treated 25 min. The effect of lignin removal rate on the enzymatic hydrolysis degree of cellulose during the treatment process was studied. At the same time, the lignin in the optimal pretreated corn stover was separated and extracted by enzymatic acidolysis, and its structure and connection were characterized. The results showed that the alkali combined with ozone pretreatment improved the enzymatic hydrolysis degree of the cellulose while exfoliating and degrading the macromolecular lignin into small molecules. The stable crosslink structure of the lignin-cellulose-hemicellulose was destroyed, and the lignocellulosic structure changed in favor of the enzymatic hydrolysis of the cellulose.

Effects of wheat straw solid contents in fermentation media on utilization of soluble/insoluble nutrient, fungal growth and laccase production

The objective of the work was to study the effect of agri-residue solid contents (2-20% w v-1) in fermentation medium on fungal growth, soluble and insoluble nutrient consumption and laccase production. Fungal strain Ganoderma lucidium and wheat straw substrate was screened for maximum laccase production. At low solid content submerged fermentation (SmF), fungus utilized mainly soluble nutrient and was unable to access the insoluble nutrient in media due to lack of contact with solid. At high solid content solid-state fermentation (SF), fungi grew on solid surface with dense and thin hyphae, utilized mainly insoluble nutrient. At medium solid content (8% w v-1) semi-solid fermentation (sSF), fungi grew on solid substrates with network of thick intercrossed hyphae, utilized both soluble and insoluble nutrients optimally resulting in highest fungal growth and laccase activity (~ 3.5 folds than in SmF and ~ 2.5 folds than in SF). Importance of soluble and insoluble nutrients was also established after isolation of their individual effects. Morphology of fungal growth (SEM), composition, thermal analysis (TGA/DTG) of substrates confirmed the results. sSF showed potential for the production of enzymes through utilization of agricultural residues as substrate.

Oxygen-radical pretreatment promotes cellulose degradation by cellulolytic enzymes

BACKGROUND

The efficiency of cellulolytic enzymes is important in industrial biorefinery processes, including biofuel production. Chemical methods, such as alkali pretreatment, have been extensively studied and demonstrated as effective for breaking recalcitrant lignocellulose structures. However, these methods have a detrimental effect on the environment. In addition, utilization of these chemicals requires alkali- or acid-resistant equipment and a neutralization step.

RESULTS

Here, a radical generator based on non-thermal atmospheric pressure plasma technology was developed and tested to determine whether oxygen-radical pretreatment enhances cellulolytic activity. Our results showed that the viscosity of carboxymethyl cellulose (CMC) solutions was reduced in a time-dependent manner by oxygen-radical pretreatment using the radical generator. Compared with non-pretreated CMC, oxygen-radical pretreatment of CMC significantly increased the production of reducing sugars in culture supernatant containing various cellulases from Phanerochaete chrysosporium. The production of reducing sugar from oxygen-radical-pretreated CMC by commercially available cellobiohydrolases I and II was 1.7- and 1.6-fold higher, respectively, than those from non-pretreated and oxygen-gas-pretreated CMC. Moreover, the amount of reducing sugar from oxygen-radical-pretreated wheat straw was 1.8-fold larger than those from non-pretreated and oxygen-gas-pretreated wheat straw.

CONCLUSIONS

Oxygen-radical pretreatment of CMC and wheat straw enhanced the degradation of cellulose by reducing- and non-reducing-end cellulases in the supernatant of a culture of the white-rot fungus P. chrysosporium. These findings indicated that oxygen-radical pretreatment of plant biomass offers great promise for improvements in lignocellulose-deconstruction processes.

Severe Disseminated Necrotizing and Granulomatous Lymphadenitis and Encephalitis in a Dog Due to Sporotrichum pruinosum (Teleomorph: Phanerochaete chrysosporium)

A 9-year-old female mixed breed dog presented for an acute onset of anorexia, vomiting, and cough. Initial examination and diagnostics revealed a large multilobular cranial mediastinal mass with unidentified fungal organisms on cytology. The disease progressed in spite of therapy until the dog was euthanized 8 months later. Gross necropsy findings were a large multilobular intrathoracic mass, mild pleuritis, and generalized lymphadenopathy. Histologic evaluation showed granulomatous inflammation and necrosis with numerous 20- to 70-micron, periodic acid–Schiff- and Gomori methenamine silver-positive spherules effacing lymph node parenchyma, as well as severe inflammation within the midbrain. Endosporulation was a common finding, and large numbers of fungal hyphae were also present in affected areas. Ribosomal RNA gene sequencing found 100% identity to published sequences of Phanerochaete chrysosporium, the teleomorph form of Sporotrichum pruinosum. This is the first published report of disease caused by natural infection with this basidiomycete organism in animals.

Physiological Peculiarities of Lignin-Modifying Enzyme Production by the White-Rot Basidiomycete Coriolopsis gallica Strain BCC 142

Sixteen white-rot Basidiomycota isolates were screened for production of lignin-modifying enzymes (LME) in glycerol- and mandarin peel-containing media. In the synthetic medium, Cerrena unicolor strains were the only high laccase (Lac) (3.2–9.4 U/mL) and manganese peroxidase (MnP) (0.56–1.64 U/mL) producers while one isolate Coriolopsis gallica was the only lignin peroxidase (LiP) (0.07 U/mL) producer. Addition of mandarin peels to the synthetic medium promoted Lac production either due to an increase in fungal biomass (Funalia trogii, Trametes hirsuta, and T. versicolor) or enhancement of enzyme production (C. unicolor, Merulius tremellosus, Phlebia radiata, Trametes ochracea). Mandarin peels favored enhanced MnP and LiP secretion by the majority of the tested fungi. The ability of LiP activity production by C. gallica, C. unicolor, F. trogii, T. ochracea, and T. zonatus in the medium containing mandarin-peels was reported for the first time. Several factors, such as supplementation of the nutrient medium with a variety of lignocellulosic materials, nitrogen source or surfactant (Tween 80, Triton X-100) significantly influenced production of LME by a novel strain of C. gallica. Moreover, C. gallica was found to be a promising LME producer with a potential for an easy scale up cultivation in a bioreactor and high enzyme yields (Lac-9.4 U/mL, MnP-0.31 U/mL, LiP-0.45 U/mL).

Redox-mediator-free degradation of sulfathiazole and tetracycline using Phanerochaete chrysosporium

The removal of two of the most commonly used antibiotics, tetracycline (TC) and sulfathiazole (STZ), using laccase-producing Phanerochaete chrysosporium was studied in liquid-phase batch experiments in the absence of any synthetic redox mediator. The removal of STZ and TC from single antibiotic spikes varied from 97.8% to 15.4% and 98.8% to 31%, respectively, with increasing initial doses of 10-250 mg L^-1 within 14 days of incubation. The enzyme activity of P. chrysosporium was only minimally influenced by the concentrations of these antibiotics. The degradation of antibiotics initiated before an appreciable extracellular enzyme activity was noted in the fungal culture. The appearance of low-molecular weight molecular fragments from parent antibiotics in liquid chromatography-mass spectrometry confirmed the biodegradation process.

White-rot fungi pretreatment combined with alkaline/oxidative pretreatment to improve enzymatic saccharification of industrial hemp

White-rot fungi combined with alkaline/oxidative (A/O) pretreatments of industrial hemp woody core were proposed to improve enzymatic saccharification. In this study, hemp woody core were treated with only white rot fungi, only A/O and combined with the two methods. The results showed that Pleurotus eryngii (P. eryngii) was the most effective fungus for pretreatment. Reducing sugars yield was 329mg/g with 30 Filter Paper Unit (FPU)/g cellulase loading when treated 21day. In the A/O groups, the results showed that when treated with 3% NaOH and 3% H₂O₂, the yield of reducing sugars was 288mg/g with 30FPU/g cellulase loading. After combination pretreatment with P. eryngii and A/O pretreatment, the reducing sugar yield from enzymatic hydrolysis of combined sample increased 1.10-1.29-fold than that of bio-treated or A/O pretreatment sample at the same conditions, suggesting that P. eryngii combined with A/O pretreatment was an effective method to improve enzyme hydrolysis.

Enhancement in multiple lignolytic enzymes production for optimized lignin degradation and selectivity in fungal pretreatment of sweet sorghum bagasse

The objective of this work was to study the increase in multiple lignolytic enzyme productions through the use of supplements in combination in pretreatment of sweet sorghum bagasse (SSB) by Coriolus versicolor such that enzymes act synergistically to maximize the lignin degradation and selectivity. Enzyme activities were enhanced by metallic salts and phenolic compound supplements in SSF. Supplement of syringic acid increased the activities of LiP, AAO and laccase; gallic acid increased MnP; CuSO₄ increased laccase and PPO to improve the lignin degradations and selectivity individually, higher than control. Combination of supplements optimized by RSM increased the production of laccase, LiP, MnP, PPO and AAO by 17.2, 45.5, 3.5, 2.4 and 3.6 folds respectively for synergistic action leading to highest lignin degradation (2.3 folds) and selectivity (7.1 folds). Enzymatic hydrolysis of pretreated SSB yielded ∼2.43 times fermentable sugar. This technique could be widely applied for pretreatment and enzyme productions.

Induction of fungal laccase production under solid state bioprocessing of new agroindustrial waste and its application on dye decolorization

Lignocellulosic wastes are generally produced in huge amounts worldwide. Peach waste of these obtained from fruit juice industry was utilized as the substrate for laccase production by Pleurotus eryngii under solid state bioprocessing (SSB). Its chemical composition was determined and this bioprocess was carried out under stationary conditions at 28 °C. The effects of different compounds; copper, iron, Tween 80, ammonium nitrate and manganese, and their variable concentrations on laccase production were investigated in detail. The optimum production of laccase (43,761.33 ± 3845 U L^-1) was achieved on the day of 20 by employing peach waste of 5.0 g and 70 µM Cu²⁺, 18 µM Fe²⁺, 0.025% (v/v) Tween 80, 4.0 g L^-1 ammonium nitrate, 750 µM Mn²⁺ as the inducers. The dye decolorization also researched to determine the degrading capability of laccase produced from peach culture under the above-mentioned conditions. Within this scope of the study, methyl orange, tartrazine, reactive red 2 and reactive black dyes were treated with this enzyme. The highest decolorization was performed with methyl orange as 43 ± 2.8% after 5 min of treatment when compared to other dyes. Up to now, this is the first report on the induction of laccase production by P. eryngii under SSB using peach waste as the substrate.

Characterization of Unexplored Deadwood Mycobiome in Highly Diverse Subtropical Forests Using Culture-independent Molecular Technique

The deadwood mycobiome, also known as wood-inhabiting fungi (WIF), are among the key players in wood decomposition, having a large impact on nutrient cycling in forest soils. However, our knowledge of WIF richness and distribution patterns in different forest biomes is limited. Here, we used pyrotag sequencing of the fungal internal transcribed spacer (ITS2) region to characterize the deadwood mycobiome of two tree species with greatly different wood characteristics (Schima superba and Pinus massoniana) in a Chinese subtropical forest ecosystem. Specifically, we tested (i) the effects of tree species and wood quality properties on WIF OTU richness and community composition; (ii) the role of biotic and abiotic factors in shaping the WIF communities; and (iii) the relationship between WIF OTU richness, community composition and decomposition rates. Due to different wood chemical properties, we hypothesized that the WIF communities derived from the two tree species would be correlated differently with biotic and abiotic factors. Our results show that deadwood in subtropical forests harbors diverse fungal communities comprising six ecological functional groups. We found interesting colonization patterns for this subtropical biome, where Resinicium spp. were highly detected in both broadleaved and coniferous deadwood. In addition, the members of Xylariales were frequently found in Schima. The two deadwood species differed significantly in WIF OTU richness (Pinus > Schima) and community composition (P < 0.001). Variations in WIF community composition of both tree species were significantly explained by wood pH and ecological factors (biotic: deadwood species, basal area and abiotic: soil pH), but the WIF communities derived from each tree species correlated differently with abiotic factors. Interestingly, we found that deadwood decomposition rate significantly correlated with WIF communities and negatively correlated with WIF OTU richness. We conclude that the pattern of WIF OTU richness and community composition are controlled by multiple interacting biotic and abiotic factors. Overall, our study provides an in-depth picture of the deadwood mycobiome in this subtropical forest. Furthermore, by comparing our results to results from temperate and boreal forests we contribute to a better understanding of patterns of WIF communities across different biomes and geographic locations.

Gene expression metadata analysis reveals molecular mechanisms employed by Phanerochaete chrysosporium during lignin degradation and detoxification of plant extractives

Lignin, most complex and abundant biopolymer on the earth's surface, attains its stability from intricate polyphenolic units and non-phenolic bonds, making it difficult to depolymerize or separate from other units of biomass. Eccentric lignin degrading ability and availability of annotated genome make Phanerochaete chrysosporium ideal for studying lignin degrading mechanisms. Decoding and understanding the molecular mechanisms underlying the process of lignin degradation will significantly aid the progressing biofuel industries and lead to the production of commercially vital platform chemicals. In this study, we have performed a large-scale metadata analysis to understand the common gene expression patterns of P. chrysosporium during lignin degradation. Gene expression datasets were retrieved from NCBI GEO database and analyzed using GEO2R and Bioconductor packages. Commonly expressed statistically significant genes among different datasets were further considered to understand their involvement in lignin degradation and detoxification mechanisms. We have observed three sets of enzymes commonly expressed during ligninolytic conditions which were later classified into primary ligninolytic, aromatic compound-degrading and other necessary enzymes. Similarly, we have observed three sets of genes coding for detoxification and stress-responsive, phase I and phase II metabolic enzymes. Results obtained in this study indicate the coordinated action of enzymes involved in lignin depolymerization and detoxification-stress responses under ligninolytic conditions. We have developed tentative network of genes and enzymes involved in lignin degradation and detoxification mechanisms by P. chrysosporium based on the literature and results obtained in this study. However, ambiguity raised due to higher expression of several uncharacterized proteins necessitates for further proteomic studies in P. chrysosporium.

Mycoremediation of hydrocarbons with basidiomycetes-a review

The literature on hydrocarbon remediation with basidiomycetes was reviewed. Two ecological groups are considered for bioremediation, the saprotrophic basidiomycetes (white-rot and brown-rot fungi) and the ectomycorrhizal basidiomycetes. A remarkable capacity of basidiomycetes for in vitro degradation of simple and recalcitrant hydrocarbons, such as PAH, persistent organic pollutants (POPs), halogenated HC, aromatic HC and phenols, explosives and dyes was reported for many species. However, there is a need for more studies on the practical feasibility of field applications with basidiomycetes.

Pleurotus ostreatus decreases cornstalk lignin content, potentially improving its suitability for animal feed

BACKGROUND

The capacity of Pleurotus ostreatus to degrade lignin was investigated in the fermentation of cornstalk. Cornstalk was incubated with P. ostreatus for 30 days, and acid-soluble and acid-insoluble lignins were assessed. The microscopic structure of cornstalk samples was studied by scanning electron microscopy (SEM), and spectroscopic characteristics were measured by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (¹³ C NMR) spectroscopy.

RESULTS

During fermentation of cornstalk, the proportion of acid-soluble lignin did not vary significantly (P > 0.05), but that of acid-insoluble lignin decreased gradually from 17.8% on day 0 to 7.6% on day 30 (P < 0.01). SEM revealed that the surface of cornstalk was gradually damaged with cavities increasing in number and size, forming a quasi-network structure. Crystallinity decreased from 35.0 on day 0 to 15.2 on day 30. FTIR and cross-polarization magic angle spinning (CPMAS) ¹³ C NMR spectra showed that the intensity of the peaks corresponding to lignin, cellulose and hemicellulose also decreased gradually over 30 days.

CONCLUSION

Cornstalk can be effectively degraded by P. ostreatus within 30 days. Pleurotus ostreatus decreases cornstalk lignin content, potentially improving its suitability for animal feed. © 2016 Society of Chemical Industry.