A new assay for lignin-type peroxidases employing the dye azure B

Biodegradation of Naphthalene Using Biosurfactant Producing Fusarium proliferatum WC416 Isolated from Refinery Effluent

Naphthalene is one of the priority pollutants in the environment which can effectively managed through bioremediation approach. Here fungal remediation of PAHs may be cost-effective technology. In present research study, biodegradation of naphthalene at varying concentrations in laboratory scale was investigated using Fusarium proliferatum WC416 isolated from refinery effluent. Degradation of naphthalene was computed by high-performance liquid chromatography (HPLC) and gas chromatography -mass spectroscopy (GC-MS). The results show that Fusarium proliferatum WC416 has effectively degraded the naphthalene to salicylamide and salicylic acid. The highest degradation achieved was 83% for the concentration of 100 ppm followed 74% and 63% for the concentration of 250 ppm and 500 ppm respectively. The intermediates confirmed by GC-MS were salicylic acid (m/z identification 138) and salicylamide (m/z identification 137). During the study, fungal growth, COD, pH, and surface tension have been monitored, which show the continuous variation that indicates progressive biodegradation of naphthalene. The qualitative assessment of extracellular enzymes shows positive activity for lipase, manganese peroxidase, and laccase. The present study also assessed the biosurfactant production by fungus which was characterized as sophorolipid in nature. The study suggests that Fusarium proliferatum WC416 would be an efficient degrader of naphthalene for environmental clean-up.

Effect of co-cultivation of white and brown rot species on basidiome production, lignocelluloytic enzyme activity and dye decolourisation

The aim of this work was studying the impact of co-cultivating two mushroom species: a white (Pleurotus albidus CLA 45) and a brown rot one (Laetiporus sulphureus BAFC 205) in substrates based on poplar or pine sawdust, on their lignocellulolytic enzyme production, yield values and basidiomes properties. Laetiporus sulphureus only developed basidiome primordia, but P. albidus monoculture and co-culture in pine sawdust achieved biological efficiencies of up to 50-55 %. Co-cultivation on diverse substrates rendered varied enzyme titers. Laccase and Manganese peroxidase titers were highest in pine co-culture and P. albidus poplar monoculture, respectively. Enzymatic extracts obtained from spent poplar substrate of dual cultures displayed potential for treating non-sterile textile-coloured effluents, achieving 35 % decolourisation after 120 h. The knowledge available on the effects of co-culture of white and brown rot fungi is still limited. This study represents an initial exploration of the interaction between them within intensive cultivation conditions.

Production of Extracellular Enzymes by Lentinula edodes Strains in Solid-State Fermentation on Lignocellulosic Biomass Sterilized by Physical and Chemical Methods

Two methods of sterilization of lignocellulosic biomass were performed in this study. Eucalypt waste (EW) supplemented with rice bran (RB) was added in the proportions 80:20 and 90:10 in dry weight. The compositions were sterilized by physical method (autoclaving) and by chemical method (H2O2). The production of extracellular enzymes by Lentinula edodes strains was compared within the two methods. Inactivation of catalase present in RB was achieved with 250 mM H2O2. The use of H2O2, when compared by physical method, favored high production of hydrolytic enzymes such as endoglucanase (1,600 IU/kg), twofold higher, β-glucosidase (1,000 IU/kg), fivefold higher, xylanase (55,000 IU/kg), threefold higher and β-xylosidase (225 IU/kg), similar results. Oxidative enzymes, MnP and laccase, were produced within a different profile between strains, with shorter times for laccase (2,200 IU/kg) by SJC in 45 days and MnP (2,000 IU/kg) by CCB-514 in 30 days. High production of extracellular enzymes is achieved by the use of the chemical method of sterilization of lignocellulosic biomass; in addition to no energy consumption, this process is carried out in a shorter execution time when compared to the physical process. The use of H2O2 in sterilization does not produce toxic compounds from the degradation of hemicellulose and cellulose such as furfural and hydroxy-methyl-furfural that cause inhibition of microorganisms and enzymes.

Live Biomass of Rigidoporus vinctus: A Sustainable Method for Decoloration and Detoxification of Dyes in Water

In this study, white-rot fungus, Rigidoporus vinctus, collected from an unidentified fallen twig from Pathankot, Punjab, India, was used for biosorption of anionic Congo red and cationic Methylene blue dyes from an aqueous medium. The biosorption efficiency of the live biomass of Rigidoporus vinctus was investigated to optimize biosorbent dosage, process time, concentrations of dyes, and pH of solutions. The results indicated that Rigidoporus vinctus is more efficient than other reported bio-adsorbents for Congo red and Methylene blue dyes. The maximum biosorption activity of Rigidoporus vinctus for Congo red was found at pH 2, and that for Methylene blue was at pH 10, after 24 h of the reaction period. The process followed pseudo-second-order kinetics, which indicated that the interaction of both dyes to the adsorption sites on the surface of Rigidoporus vinctus was responsive to biosorption. The biosorption process could be well explained by the Langmuir isotherm for both dyes. The maximum monolayer biosorption capacity of Rigidoporus vinctus for Congo red and Methylene blue was observed to be 54.0 mg/g and 80.6 mg/g, respectively. The seed germination test was carried out, and it was assessed that the toxicity of dyes was reduced up to significant levels. Based on the present experimental findings, it can be concluded that biosorption using the live biomass of Rigidoporus vinctus can effectively decolorize dye-containing wastewater, thus reducing the hazardous effects of dyes on human beings.

Abatement of microfibre pollution and detoxification of textile dye - Indigo by engineered plant enzymes

Microfibres (diameter <5 mm) and textile dyes released from textile industries are ubiquitous, cause environmental pollution, and harm aquatic flora, fauna, animals and human life. Therefore, enzymatic abatement of microfibre pollution and textile dye detoxification is essential. Microbial enzymes for such application present major challenges of scale and affordability to clean up large scale pollution. Therefore, enzymes required for the biodegradation of microfibres and indigo dye were expressed in transplastomic tobacco plants through chloroplast genetic engineering. Integration of laccase and lignin peroxidase genes into the tobacco chloroplast genomes and homoplasmy was confirmed by Southern blots. Decolorization (up to 86%) of samples containing indigo dye (100 mg/L) was obtained using cp-laccase (0.5% plant enzyme powder). Significant (8-fold) reduction in commercial microbial cellulase cocktail was achieved in pretreated cotton fibre hydrolysis by supplementing cost effective cellulases (endoglucanases, ß-glucosidases) and accessory enzymes (swollenin, xylanase, lipase) and ligninases (laccase lignin peroxidase) expressed in chloroplasts. Microfibre hydrolysis using cocktail of Cp-cellulases and Cp-accessory enzymes along with minimal dose (0.25% and 0.5%) of commercial cellulase blend (Ctec2) showed 88%-89% of sugar release from pretreated cotton and microfibres. Cp-ligninases, Cp-cellulases and Cp-accessory enzymes were stable in freeze dried leaves up to 15 and 36 months respectively at room temperature, when protected from light. Use of plant powder for decolorization or hydrolysis eliminated the need for preservatives, purification or concentration or cold chain. Evidently, abatement of microfibre pollution and textile dye detoxification using Cp-enzymes is a novel and cost-effective approach to prevent their environmental pollution.

Biodegradation and detoxification of phenanthrene in in vitro and in vivo conditions by a newly isolated ligninolytic fungus Coriolopsis byrsina strain APC5 and characterization of their metabolites for environmental safety

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant organic pollutants generated from agricultural, industrial, and municipal sources, and their strong carcinogenic and teratogenic properties pose a harmful threat to human beings. The present study deals with the bioremediation of phenanthrene by a ligninolytic fungus, Coriolopsis byrsina (Mont.) Ryvarden strain APC5 (GenBank; KY418163.1), isolated from the fruiting body of decayed wood surface. During the experiment, Coriolopsis byrsina strain APC5 was found as a promising organism for the degradation and detoxification of phenanthrene (PHE) in in vitro and in vivo conditions. Further, HPLC analysis showed that the C. byrsina strain degraded 99.90% of 20 mg/L PHE in in vitro condition, whereas 77.48% degradation of 50 mg/L PHE was reported in in vivo condition. The maximum degradation of PHE was noted 25 °C temperature under shaking flask conditions at pH 6.0. Further, GC-MS analysis of fungal treated samples showed detection of 9,10-Dihydroxy phenanthrene, 2,2-Diphenic acid, phthalic acid, 4-heptyloxy phenol, benzene octyl, and acetic acid anhydride as the metabolic products of degraded PHE. Furthermore, the phytotoxicity evaluation of degraded PHE was observed through the seed germination method using Vigna radiata and Cicer arietinum seeds. The phytotoxicity results showed that the seed germination index and vegetative growth parameters of tested plants were increased in the degraded PHE soil. As results, C. byrsina strain APC5 was found to be a potential and promising organism to degrade and detoxify PHE without showing any adverse effect of their metabolites.

Seasonal variation and tissues specificity of endophytic fungi of Dillenia indica L. and their extracellular enzymatic activity

Endophytes are microbes that live inside the tissues of plants without causing any disease. Many of these belonging to fungi have been exploited earlier for their biological activities. This study focused on the exploration and characterization of culturable endophytic fungi inhabiting the medicinal plant Dillenia indica L. during four different seasons (summer, monsoon, autumn, and winter) from 2018 to 2019. A total of 2360 segments from different parts (leaves, fruits, and stem) were screened to isolate endophytic fungi. During the study, 25 species of fungi belonging to 20 genera were isolated from the selected plant. The identification of these fungi was validated at morphological, microscopic, and molecular levels. Results indicate the plant has the highest affinity for Daldinia eschscholtzii, followed by Colletotrichum gloeosporioides and Cladosporium cladosporioides. Further, the percent frequency was highest in leaves, followed by stem and fruits. The results were further supported by a similar trend of colonization rate for different plant parts. The monsoon season had the highest number of isolates (312), followed by summer (208), winter (164), and autumn (114). Species diversity was highest during the monsoon season and lowest during the winter. These fungi also produce amylase, lipase, protease, asparaginase, cellulase, and ligninolytic enzymes. This study focused only on culturable fungal endophytes, yet the scope can be extended for other non-culturable microbes and their interaction by using high-throughput genomics and novel next-generation sequencing (NGS) tools. The results indicate that Dillenia indica L. harbors novel endophytic fungi having industrial applications.

Degradation and detoxification of reactive yellow dyes by Scedosporium apiospermum: a mycoremedial approach

Textile industrial effluents have long enunciated the essentiality of ascertaining an efficient wastewater treatment for the removal of azo dyes given their potential disturbances on the ecosystem. Our study investigated the efficiency of the strain SKF2 among 14 other isolates, molecularly identified to be Scedosporium apiospermum, isolated by our research group from the textile effluent sludge in the degradation of two azo dyes, Reactive Yellow 145 and Remazol Yellow RR. Kinetic profiling of the degradation process revealed the decolourisation efficiency to be 94.8 and 86.9% for RY 145 and RYRR, respectively, during the declining growth phase. Laccase and polyphenol oxidase (RY 145-2.37 and RYRR-2.30 U/mL; RY 145-3.26 and RYRR-2.89 U/mL, respectively) were found to influence the biodegradation process in both the dyes than the other examined fungal degradative enzymes. The metabolic pathway predicted with the aid of GC-MS analysis identified the degraded metabolites to be smaller molecular weight non-toxic products. Assessment of toxicity via brine shrimp lethality assay (RY 145-23.3% and RYRR-16.7%, respectively) and seed germination assay (RY 145-96.7% and RYRR-83.3%) further solidified the detoxified status of both the dyes after biodegradation. The experimental data thus substantiated the expediency of S. apiospermum SKF2 in the degradation of textile azo dyes and its further employment in the bioremediation of textile wastewaters for agricultural applications and ecological recycling.

Microbe assisted depolymerization of lignin rich waste and its conversion to gaseous biofuel

Biomethanation potential of lignin rich residue (LRR) obtained from lignocellulosic ethanol fermentation was evaluated after subjecting to microbe assisted pretreatment using selectively enriched lignin depolymerizing consortia (LDC). The efficiency of LDC in lignin depolymerization was established using alkali and dealkali lignins (AL and DL) along with LRR as feedstocks. Microbial growth on media having lignin as sole carbon source, activity of lignin depolymerizing enzymes, viz., lignin peroxidase and laccase, ability of culture to decolorize the lignin mimicking dyes like methylene blue and ramezol brilliant blue, were considered to confirm the efficiency of enriched mixed culture. Microbial treatment using LDC showed significant positive impact on lignin breakdown irrespective of the substrate (LRR, 46.33%; AL, 31.37%; DL, 34.20%). The hydrolysate of LRR obtained from microbial pretreatment showed higher biogas yield (424 ml/g VS) owing to the efficiency of lignin depolymerization and availability of readily available biodegradable components in residual lignin from previous processing. Depolymerization of commercial lignins also produced a good amount of biogas (302-324 ml/g VS) after pretreatment with LDC. Overall, an additional energy conversion efficiency of about 11.75 kJ/g VS was obtained by valorizing the residual lignin through integrating biomethanation technology to ethanol fermentation. Outcome of this study indicated the feasibility of using lignin rich residue generated from the second generation cellulosic bioethanol plants as a potential feedstock to meet the current gaseous fuel demands. This integration also helps in closing the biomass based biorefinery loop and also promotes the circular economy.

Biodegradation of Reactive Red 198 by textile effluent adapted microbial strains

A sustainable technology to eliminate the persistent reactive dyes from the textile effluents discharged indiscriminately in the environment is highly desirous given the explosive growth of textile industries. The present study investigated the potential of two different bacterial strains, Bacillus cereus SKB12 and Enterobacter hormaechei SKB16 isolated from the dye house effluent sludge in the biotransformation of Reactive Red 198 (RR 198). Process variables such as temperature, pH, shaking conditions and contact time were optimized for the successful decolourization of RR 198. Maximum decolourization of 80% and 85% of RR 198 was achieved at pH 6 and 7, and 40 °C in microaerophilic conditions on treatment with B. cereus and E. hormaechei, respectively. High-Performance Liquid Chromatography (HPLC), and Gas Chromatography-Mass Spectrometry (GC-MS) analyses conducted further affirmed that the decolourization of RR 198 was rather due to biodegradation than biosorption through shift in wavenumbers, retention time variations and the appearance of lesser molecular weight peaks. Degradative pathway for RR 198 predicted based on the enzyme assay data and dye degraded metabolite peaks acquired through GC-MS analysis highlighted the significance of azoreductase and laccase in the degradation of RR 198 into smaller non-toxic compounds. In addition, toxicity assessment through zootoxicological and phytotoxicological experiments using brine shrimp and Vigna radiata validated the detoxified status of the metabolites thus proving the promising potentials of the bacterial strains in the remediation of azo dyes.

Ligninolytic valorization of agricultural residues by Aspergillus nomius and Trichoderma harzianum isolated from gut and comb of Odontotermes obesus (Termitidae)

Fungi produce enzymes that degrade the complex lignin thereby enabling the efficient utilization of plant lignocellulosic biomass in the production of biofuel and cellulose-based products. In the present study, the agricultural residues such as paddy straw, sugarcane bagasse, and coconut husk were used as substrates for the biodegradation by Aspergillus nomius (MN700028) and Trichoderma harzianum (MN700029) isolated from gut of the termite, Odontotermes obesus and fungus comb in the termite mound, respectively. The influence of varying concentrations of different carbon sources, pH, and temperature on ligninolytic enzyme production was examined under laboratory conditions. The highest activities of manganese peroxidase (0.24 U/mL), lignin peroxidase (10.38 U/mL) and laccase (0.05 U/mL) were observed under studied conditions. Fungal pretreatment of lignocellulosic biomass for 45 days showed that A. nomius and T. harzianum degraded 84.4% and 81.66% of hemicelluloses, 8.16% and 93.75% of cellulose, and 52.59% and 65% of lignin, respectively. The interaction of pH, temperature, and different carbon sources with fungal biomass and enzyme production was found significant (p ≤ 0.05). SEM analysis indicated alterations in the microstructures of degraded lignocellulosic substrates. A. nomius and T. harzianum were highly efficient in ligninolytic enzymes production and in vitro digestibility of agricultural residues. The study reports the production of laccase by A. nomius isolated from termite gut for the first time. The fungal isolates A. nomius and T. harzianum posses potential for ligninocellulosic waste degradation.

Isolation and Screening of Microorganisms for the Effective Pretreatment of Lignocellulosic Agricultural Wastes

Lignocellulosic waste is the most abundant biorenewable biomass on earth, and its hydrolysis releases highly valued reducing sugars. However, the presence of lignin in the biopolymeric structure makes it highly resistant to solubilization thereby hindering the hydrolysis of cellulose and hemicellulose. Microorganisms are known for their potential complex enzymes that play a dominant role in lignocellulose conversion. Therefore, the current study was designed to isolate and screen potential microorganisms for their selective delignification ability for the pretreatment of lignocellulosic biomass. An extensive isolation and screening procedure yielded 36 desired isolates (22 bacteria, 7 basidiomycete fungi, and 7 filamentous fungi). Submerged cultivation of these desired microorganisms revealed 4 bacteria and 10 fungi with potent lignocellulolytic enzyme activities. The potent isolates were identified as Pleurotus, Trichoderma, Talaromyces, Bacillus, and Chryseobacterium spp. confirmed by morphological and molecular identification. The efficiency of these strains was determined through enzyme activities, and the degraded substrates were analyzed through scanning electron microscopy (SEM) and X-ray diffraction (XRD). Among all isolated microbes, Pleurotus spp. were found to have high laccase activity. The cellulose-decomposing and selective delignification strains were subjected to solid-state fermentation (SSF). SSF of field waste corn stalks as a single-carbon source provides Pleurotus spp. better condition for the secretion of ligninolytic enzymes. These isolated ligninolytic enzymes producing microorganisms may be used for the effective pretreatment of lignocellulosic agricultural wastes for the production of high value-added natural products by fermentation.

Characteristics and functional bacteria in a microbial consortium for rice straw lignin-degrading

The degradation of lignin is the main rate-limiting step in the bio-pulping of rice straw. A lignin-degrading bacterial consortium LDC, which can efficiently degrade lignin of reed, was screened in the early stage of our laboratory work. In present study, 7-day incubation of LDC can degrade rice straw lignin by 31.18% in mineral salt medium. The communities' structure of different incubation phases varied greatly, in which high abundance (44.78%) of Anaerocolumna was first found. The expression levels of lignin degradation enzyme class II peroxidase (AA2), vanillyl alcohol oxidase (AA4) and 1,4-benzoquinone reductase (AA6) during peak phase (48 h) were significantly up-regulated than initial phase (24 h), increasing by 112%, 165% and 67%, respectively, and 42.86% AA2 was from Thaurea; 100% AA4 was from Clostridium; 62.5% AA6 was from Pseudomonas. These provide microbial resources and data support for the industrialization of rice straw bio-pulping.

Qualitative and Molecular Screening of Potential Ligninolytic Microbes from Termite (Coptotermes curvignathus) Gut

Ligninolytic microbes have great potential in converting high lignin by-products to more utilisable products by decomposing the lignin-rich agricultural and industrial wastes. Thus, the aim of this study are to screen and identify the potential ligninolytic microbes from the termite (Coptotermes curvignathus) gut. The study was conducted at Universiti Putra Malaysia Bintulu Sarawak Campus, Malaysia. Twenty-seven microbes isolated from termite gut obtained from the Microbiology Laboratory, Faculty of Agricultural Science and Forestry, were used for the ligninolytic activity screening. Media with four different ligninolytic indicator dyes (Azure B, phenol red, methylene blue, and Remazol Brilliant Blue) were streaked with microbial isolates and incubated at 37 °C for 48 h. Out of twenty-seven microbe isolates, only three (CH2, CH5, and CH9) isolates showed decolourisation zone indicating the positive presence of ligninolytic activity. The 16S rRNA gene sequence data indicated the isolates are highly homologous to Bacillus spp.

The vibronic absorption spectrum and electronic properties of Azure B in aqueous solution: TD-DFT/DFT study

The vibronic absorption spectrum of Azure B (AB) in an aqueous solution is calculated using the time-dependent density functional theory (TD-DFT). The results of calculations are analyzed using all hybrid functionals supported by Gaussian16, the 6-31++G(d,p) basis set, and the IEFPCM and SMD solvent models. The solvent model IEFPCM gave significantly underestimated values of λ_max in comparison with the experiment. This is a manifestation of the TD-DFT "cyanine failure". However, the SMD model made it possible to obtain good agreement between the calculation results and experimental data. The best fit was achieved using the X3LYP functional. According to our calculations, the shoulder in the visible absorption spectrum of AB has a vibronic origin. However, the calculated shoulder is weaker than the experimental one. Explicit assignment of two water molecules, which form strong hydrogen bonds with a dye molecule, leads to a shift of the calculated absorption spectrum to longer wavelengths by approximately 17 nm but does not lead to an improvement in its shape. Comparative analysis of the calculated vibronic absorption spectra of Azure B with those obtained earlier for Azure A and methylene blue showed that the presence and intensity of the short-wavelength shoulder are determined by the location of the bands of higher vibronic transitions relative to the band of the 0₀ → 0⁰ main transitions. Photoexcitation leads to an increase in the dipole moment of the dye molecule. An insignificant photoinduced electron transfer was found in the central ring of the chromophore of the dye molecule.

Current Knowledge on the Fungal Degradation Abilities Profiled through Biodeteriorative Plate Essays

Fungi are known to contribute to the development of drastic biodeterioration of historical and valuable cultural heritage materials. Understandably, studies in this area are increasingly reliant on modern molecular biology techniques due to the enormous benefits they offer. However, classical culture dependent methodologies still offer the advantage of allowing fungal species biodeteriorative profiles to be studied in great detail. Both the essays available and the results concerning distinct fungal species biodeteriorative profiles obtained by amended plate essays, remain scattered and in need of a deep summarization. As such, the present work attempts to provide an overview of available options for this profiling, while also providing a summary of currently known fungal species putative biodeteriorative abilities solely obtained by the application of these methodologies. Consequently, this work also provides a series of checklists that can be helpful to microbiologists, restorers and conservation workers when attempting to safeguard cultural heritage materials worldwide from biodeterioration.

Functional expression and characterization of two laccases from the brown rot Fomitopsis pinicola

Laccase is predominantly found in lignin degrading filamentous white rot fungi, where it is involved in the oxidative degradation of this recalcitrant heteropolymer. In brown rot fungi it is much less prevalent: laccases from only a few brown rots have been detected and only two have been characterized. This study tries to understand the role of this ligninolytic enzyme in brown rots by investigating the catalytic properties of laccases secreted by Fomitopsis pinicola FP58527 SS1. When grown on either poplar or spruce wood blocks, several laccases were detected in the secretome. Two of them (FpLcc1 and FpLcc2) were heterologously produced using Trichoderma reesei QM9414 Δxyr1 as expression host and purified to homogeneity by consecutive steps of hydrophobic interaction, anion exchange and size exclusion chromatography. With the substrates 2,2-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS), 2,6-dimethoxyphenol (2,6-DMP) and guaiacol both laccases showed similar, low pH-optima below 3 for ABTS and 2,6-DMP and at pH 3.5 for guaiacol which is at the acidic end of laccases isolated from white rot fungi. The determined K_M values were low while k_cat values measured at acidic conditions were comparable to those reported for other laccases from white rot fungi. While both enzymes showed a moderate decrease in activity in the presence of oxalic and citric acid FpLcc2 was activated by acetic acid up to 3.7 times. This activation effect is much more pronounced at pH 5.0 compared to pH 3.0 and could already be observed at a concentration of 1 mM acetic acid.

In silico exploration of lignin peroxidase for unraveling the degradation mechanism employing lignin model compounds

Lignin peroxidase is a heme-containing biocatalyst, well-known for its diverse applications in the fields from environmental chemistry to biotechnology. LiP-mediated oxidative catalysis is H₂O₂-dependent, and can oxidize phenolic, and non-phenolic substrates by oxidative cleavage of the C-C and C-O bonds of lignin. In contrast to fungi-derived LiP, the binding affinity of bacterial-derived LiP to lignin at the molecular level is poorly known to date. Tremendous wet-lab studies have been unveiled that provide degradation and biotransformation information on kraft lignin, whilst studies on the completely transformed compounds and the degradation of each transformed compounds simultaneously during degradation are scarce. To gain an understanding of the degradation process using docking, and MDS based studies, we assessed the binding affinity of selected lignin model compounds with bacterial origin LiP and validated such docked complexes exploiting 30 ns molecular dynamics simulations. We selected and picked a total of 12 lignin model compounds for molecular modeling analysis, namely two chlorinated lignin model compounds (monomer) (2-chlorosyringaldehyde and 5-chlorovanillin), eight standard lignin model compounds (veratryl alcohol, syringyl alcohol, sinapyl alcohol, methyl hydroquinone, guaiacol, coniferyl alcohol, catechol, and 4-methoxy phenol), while, two 4-O-5, and β-O-4 linkage-based multimeric model compounds (dimer: 2-methoxy-6-(2-methoxy-4-methylphenoxy)-4-methylphenol; trimer: syringyl β-O-4 syringyl β-O-4 sinapyl alcohol). Far more specific binding residues were observed from XP-Glide docking, as TYR, HIP (protonated histidine), PHE, VAL, ASP, THR, LYS and GLN. The binding affinity was confirmed by the Gibbs free energy or binding energy (ΔG) score; furthermore, it is found that the maximum binding energy seems to be observed for 4-methoxyphenol with a Glide score of -3.438 with Pi-Pi stacking and H-bond type bonding interactions, whilst the lowest XP Gscore as -8.136 with Pi-Pi stacking and H-bond (side chain) type bonding interactions were found for the trimer model compound. The docked complexes were further evaluated for deep rigorous structural and functional fluctuation analyses through high-performance molecular dynamics simulations-DESMOND, after a post simulation run of 30 ns. The RMSD trajectory analyses of the protein-ligands were found to be in the equilibrium state at the end of simulation run for multimeric lignin model compounds. In addition, ionic ligand-protein interaction occurs among chlorinated compounds, while hydrophobic and H-bond contacts have frequently been observed in all lignin-model compounds. The findings herein demonstrate that bacterial LiP can effectively catalyze multiple lignin model compounds, and it might further be used as an effective tool for sustainable mitigation of diverse environmental contaminants.

Evaluation of the lignite biotransformation capacity of Fusarium sp. NF01 cultured on different growth substrates

The screening and studying the lignite solubilization/degradation capacities of indigenous microorganisms are key to exploring the in-situ biotransformation of lignite. Herein, a fungus was isolated from in-situ lignite samples and identified as Fusarium sp. NF01. This isolate was then cultured on four different carbon sources to evaluate its lignite-transformation capacity. When cultured on a solid agar medium containing sodium gluconate or sodium glutamate, Fusarium sp. NF01 completely liquefied 0.5 g of lignite within 6 days, and when cultured in a liquid medium containing sodium gluconate, the weight of lignite decreased by 28.4% within 7 days. Elemental analysis showed that the rate of lignite biodegradation was inversely proportional to the C:O ratio of the residual lignite samples. Additionally, a 5.9% biodesulfurization rate was achieved when Fusarium sp. NF01 was cultured in the presence of sodium gluconate. Finally, Fourier-transform infrared analysis of the residual lignite samples revealed relatively weak signal intensities of the signature peaks representing the following: aromatic ring side chains; ether, ester, and alcohol bonds; aromatic ring carbon-carbon double bonds; and aliphatic methyl and methylene. The results show that Fusarium sp. NF01 degrades lignite in a carbon-dependent manner and could be thus used for the bioconversion of subsurface coalbeds.

Biodegradation of fluorene by the newly isolated marine-derived fungus, Mucor irregularis strain bpo1 using response surface methodology

Fluorene, a low molecular weight polycyclic aromatic hydrocarbon (PAH), is of immense environmental interest because of its carcinogenicity, teratogenicity, mutagenicity, toxicity and persistence to microbial degradation. Existentially, there is paucity of information on PAH degradation by fungi isolated from marine environment. Therefore, this study investigated fluorene degradation efficiency of marine derived filamentous fungus, Mucor irregularis strain bpo1 (GenBank Accession Number: MK373020). Response Surface Methodology (RSM) using Box-Behnken Design (BBD) was successfully deployed in the optimization of process parameters (pH-7, temperature-32.5 °C, substrate concentration-100 mg L^-1 and dry weight-2 g) resulting in 81.50% fluorene degradation on 5th day. The design and regression model were found to be statistically significant, adequate and appropriate with p < 0.0001, F value= 202.39, and predicted coefficient of determination (R² =0.9991). Optimization of the vital constituents of the mineral salt medium (MSM) used for the study using RSM-Central Composite Design (CCD) resulted in 79.80% fluorene degradation rate. Enhanced fluorene degradation efficiency (82.50%) was recorded when the optimized process variables were subjected to growth-linked validation experiments. The enzyme activities revealed 87%, 59% and 31% induction of laccase, manganese peroxidase and lignin peroxidase respectively. Four metabolites; 9H-fluoren-9-one, benzene-1,2-dicarboxylic acid, 2-hydroxybenzoic acid and phenol obtained after the experiment were characterized and confirmed with GC-MS analysis. The findings revealed the promising potentials of M. irregularis in PAH degradation and by extension green remediation technology.

Lignin Degradation and Its Use in Signaling Development by the Coprophilous Ascomycete Podospora anserina

The filamentous fungus Podospora anserina is a good model to study the breakdown of lignocellulose, owing to its ease of culture and genetical analysis. Here, we show that the fungus is able to use a wide range of lignocellulosic materials as food sources. Using color assays, spectroscopy and pyrolysis-gas chromatography mass spectrometry, we confirm that this ascomycete is able to degrade lignin, primarily by hydrolyzing β-O-4 linkages, which facilitates its nutrient uptake. We show that the limited weight loss that is promoted when attacking Miscanthus giganteus is due to a developmental blockage rather than an inefficiency of its enzymes. Finally, we show that lignin, and, more generally, phenolics, including degradation products of lignin, greatly stimulate the growth and fertility of the fungus in liquid cultures. Analyses of the CATΔΔΔΔΔ mutant lacking all its catalases, pro-oxidants and antioxidants indicate that improved growth and fertility of the fungus is likely caused by augmented reactive oxygen species levels triggered by the presence of phenolics.

Enhanced treatment of the oil-contaminated soil using biosurfactant-assisted washing operation combined with H2O2-stimulated biotreatment of the effluent

A real crude oil-contaminated soil was treated using a two-step method: biosurfactant-assisted soil washing and the biostimulated biotreating of the effluent. The mixture of surfactin and rhamnolipid could enhance the TPH removal from an oil-contaminated soil (32 g/kg) in the soil washing operation. 86% of TPH was removed from the oil-contaminated soil in the soil washing operation under the mixed biosurfactant (surfactin + rhamnolipid) of 0.6 g/L, the soil/water ratio of 20 w/v%, the temperature of 30 °C, and the washing time of 24 h, leaving an effluent containing 5028 mg/L TPH. The effluent was efficiently biotreated in the bioprocess with 5 g/L acclimate biomass daily stimulated with 0.1 mM H₂O₂, and the concentrtion of TPH decreased to 26 mg/L within 17 d corresponding a TPH biodegradation over 99%. The biostimulation with H₂O₂ caused the production of a high amount of peroxidase that could accelerate the biodegradation of TPH. Accordingly, the findings suggest that the biosurfactant-assisted washing operation combined with the H₂O₂-stimulated biodegradation process could be an enhanced green method for efficient treatment of the heavy oil-contaminated soils.

Immobilization interaction between xenobiotic and Bjerkandera adusta for the biodegradation of atrazine

The aim of the present work is to evaluate the ability of 'fungi' for the biodegradation of recalcitrant xenobiotic compound, 'Atrazine' in batch liquid cultures. Different parameters like pH (2.0-8.0) temperature (16-32 °C), biomass (1-5 g), and concentration (25-100 ppm) were optimized for the efficient degradation of atrazine. The decomposition behavior of atrazine is analyzed with the help of Fourier Transform Infrared (FTIR) spectroscopy. Herein, we have reported that the Bjerkandera adusta possess high removal efficiency of the xenobiotic compound (atrazine) up to 92%. The fungal strain investigated could prove to be a valuable active pesticide degrading micro-organism, with high detoxification values. These results are useful for improved understanding and prediction of the behavior and fate of B. adusta in the bio-purification of wastewater contaminated with xenobiotics. Thus providing a new and green approach for the remediation of toxicants without altering the environmental components.

Enzymatic and genetic characterization of lignin depolymerization by Streptomyces sp. S6 isolated from a tropical environment

The conversion of lignocellulosic biomass into bioethanol or biochemical products requires a crucial pretreatment process to breakdown the recalcitrant lignin structure. This research focuses on the isolation and characterization of a lignin-degrading bacterial strain from a decaying oil palm empty fruit bunch (OPEFB). The isolated strain, identified as Streptomyces sp. S6, grew in a minimal medium with Kraft lignin (KL) as the sole carbon source. Several known ligninolytic enzyme assays were performed, and lignin peroxidase (LiP), laccase (Lac), dye-decolorizing peroxidase (DyP) and aryl-alcohol oxidase (AAO) activities were detected. A 55.3% reduction in the molecular weight (Mw) of KL was observed after 7 days of incubation with Streptomyces sp. S6 based on gel-permeation chromatography (GPC). Gas chromatography-mass spectrometry (GC-MS) also successfully highlighted the production of lignin-derived aromatic compounds, such as 3-methyl-butanoic acid, guaiacol derivatives, and 4,6-dimethyl-dodecane, after treatment of KL with strain S6. Finally, draft genome analysis of Streptomyces sp. S6 also revealed the presence of strong lignin degradation machinery and identified various candidate genes responsible for lignin depolymerization, as well as for the mineralization of the lower molecular weight compounds, confirming the lignin degradation capability of the bacterial strain.

Ability of Trichoderma hamatum Isolated from Plastics-Polluted Environments to Attack Petroleum-Based, Synthetic Polymer Films

Microorganisms colonizing plastic waste material collected in composting-, landfill-, and anaerobic digestion plants were isolated to obtain novel strains maximally adapted to the degradation of plastics due to long-term contact with plastic polymers. Twenty-six bacterial strains were isolated and identified by the 16 S rRNA method, and eighteen strains of yeasts and fungi using 18 S rRNA and the internal transcribed spacer ITS sequencing of the 18 S rRNA gene. In selected strains, the ability to degrade linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), polystyrene (PS), and polyvinyl chloride (PVC) was tested in aerobic liquid-medium cultures. An oxidative, two-step pretreatment of LLDPE and LDPE using γ- or UV-irradiation followed by a high-temperature treatment was carried out, and the pretreated plastics were also included in the degradation experiments. The respective weight losses after biodegradation by Trichoderma hamatum were: virgin and γ/T90-pretreated LLDPE (2.2 ± 1.2 and 3.9 ± 0.5%), virgin and UV/T60-pretreated LDPE (0.5 ± 0.4 and 1.3 ± 0.4%), and virgin PS (0.9 ± 0.4%). The Fourier transform infrared spectroscopy (FTIR) analysis showed that during the treatment of pretreated LLDPE, T. hamatum attacked low molecular weight LLDPE oligomers, reducing the functional groups (carbonyl C = O), which was paralleled by a slight increase of the molar mass of pretreated LLDPE and a decrease of the dispersity index, as demonstrated by gel permeation chromatography (GPC). Thermogravimetric analysis (TGA) highlighted the formation of functional groups on LLDPE due to polymer pretreatment that favored fungal attack at the polymer surface. The results provide insight into microbial consortia that spontaneously colonize the surface of plastics in various environments and their capability to attack plastic polymers.

The Synergistic Action of Electro-Fenton and White-Rot Fungi in the Degradation of Lignin

White-rot fungus is a common lignin-degrading fungus. However, compared with those of microorganisms that biodegrade lignin alone, synergistic systems of electro-Fenton processes and white-rot fungi are superior because of their high efficiency, mild conditions, and environmental friendliness. To investigate the details of lignin degradation by a synergistic system comprising electro-Fenton processes and white-rot fungi, lignin degradation was studied at different voltages with three lignin-degrading fungi (Phanerochaete chrysosporium, Lentinula edodes, and Trametes versicolor). The lignin degradation efficiency (82∼89%) of the synergistic systems at 4 V was higher than that of a control at 96 h post inoculation. Furthermore, the H₂O₂ produced and phenolic lignin converted in the system can significantly enhance the efficiency of ligninolytic enzymes, so a considerably increased enzyme activity was obtained by the synergistic action of electro-Fenton processes and white-rot fungi. ¹³C NMR spectroscopy revealed that aromatic structure units (103-162 ppm) were effectively degraded by the three fungi. This study shows that the combination of electro-Fenton processes and white-rot fungi treatment significantly improved the lignin degradation efficiency, which established a promising strategy for lignin degradation and valorization.

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

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

Decolorization and Detoxification of Synthetic Dyes by Mexican Strains of Trametes sp

Laccases have attracted a great deal of interest because of their remarkable ability for the degradation of synthetic dyes present in wastewaters. New laccase producing sources with robust operational and functional properties are being continuously explored. In this work, the potential for the decolorization and detoxification of synthetic dyes was evaluated in two Mexican strains of the genus Trametes. The decolorization capacity of Trametesmaxima LE130 and Trametes sp. LA1 was tested in solid and liquid media. The phytotoxicity of the degradation products was determined using Raphanussativus and Pisum sativum seeds. In solid media, both strains showed a higher decolorization capacity (p ≤ 0.05) than Phanerochaetechrysosporium ATCC 24725, which is known to be very efficient in lignin and dye-degradation. They produced laccase as the main ligninolytic enzyme; T. maxima LE130 secreted a single isoform of 43.9 kDa, while Trametes sp. LA1 produced three isoforms of 67.3, 58.6 and 52.7 kDa, respectively. Trametes sp. LA1 culture fluids were capable of decolorizing and detoxifying chemically diverse dyes (anthraquinonic dye Remazol Brilliant Blue R, azoic Reactive Black 5 and triphenylmethane Crystal Violet) without the addition of redox mediators. Therefore, this could be considered as a new laccase source which could be potentially competitive in the bioremediation of dye-containing wastewaters.

Gene Regulation Shifts Shed Light on Fungal Adaption in Plant Biomass Decomposers

Fungi dominate the turnover of wood, Earth’s largest pool of aboveground terrestrial carbon. Fungi first evolved this capacity by degrading lignin to access and hydrolyze embedded carbohydrates (white rot). Multiple lineages, however, adapted faster reactive oxygen species (ROS) pretreatments to loosen lignocellulose and selectively extract sugars (brown rot). This brown rot “shortcut” often coincided with losses (>60%) of conventional lignocellulolytic genes, implying that ROS adaptations supplanted conventional pathways. We used comparative transcriptomics to further pursue brown rot adaptations, which illuminated the clear temporal expression shift of ROS genes, as well as the shift toward synthesizing more GHs in brown rot relative to white rot. These imply that gene regulatory shifts, not simply ROS innovations, were key to brown rot fungal evolution. These results not only reveal an important biological shift among these unique fungi, but they may also illuminate a trait that restricts brown rot fungi to certain ecological niches.

Fungi dominate the recycling of carbon sequestered in woody biomass. This process of organic turnover was first evolved among “white rot” fungi that degrade lignin to access carbohydrates and later evolved multiple times toward more efficient strategies to selectively target carbohydrates—“brown rot.” The brown rot adaption was often explained by mechanisms to deploy reactive oxygen species (ROS) to oxidatively attack wood structures. However, its genetic basis remains unclear, especially in the context of gene contractions of conventional carbohydrate-active enzymes (CAZYs) relative to white rot ancestors. Here, we hypothesized that these apparent gains in brown rot efficiency despite gene losses were due, in part, to upregulation of the retained genes. We applied comparative transcriptomics to multiple species of both rot types grown across a wood wafer to create a gradient of progressive decay and to enable tracking temporal gene expression. Dozens of “decay-stage-dependent” ortho-genes were isolated, narrowing a pool of candidate genes with time-dependent regulation unique to brown rot fungi. A broad comparison of the expression timing of CAZY families indicated a temporal regulatory shift of lignocellulose-oxidizing genes toward early stages in brown rot compared to white rot, enabling the segregation of oxidative treatment ahead of hydrolysis. These key brown rot ROS-generating genes with iron ion binding functions were isolated. Moreover, transcription energy was shifted to be invested on the retained GHs in brown rot fungi to strengthen carbohydrate conversion. Collectively, these results support the hypothesis that gene regulation shifts played a pivotal role in brown rot adaptation.

Improvement of protein content and decrease of anti-nutritional factors in olive cake by solid-state fermentation: A way to valorize this industrial by-product in animal feed

The present work investigates the bioconversion of the olive cake (OC) generated by olive oil industries in Morocco through solid-state fermentation using selected filamentous fungi to increase its nutritional values for subsequent valorization as ruminants feed. The fungi, namely Beauveria bassiana, Fusarium flocciferum, Rhizodiscina cf. lignyota, and Aspergillus niger were cultured on OC for 15 days. Chemical composition as well as enzymes activities were determined. Results showed (i) an increase in protein content of up to 94% for treated OC and (ii) significant (P < 0.05) decreases of phenolic compounds, up to 43%, 70% and 42% for total phenolic content, total flavonoids content, and total condensed tannins, respectively. Moreover, the RP-HPLC analysis of fermented OC confirmed the degradation of individual phenolic compounds by the strains. These findings demonstrate that F. flocciferum and Rhizodiscina cf. lignyota are efficient enzymes producers leading to a nutritive enhancement of this by-product.

Application of quadratic regression orthogonal design to develop a composite inoculum for promoting lignocellulose degradation during green waste composting

The aims of this study are to determine the feasibility of applying QROD (quadratic regression orthogonal design) to optimize a combination of microorganisms and to develop a composite inoculum for promoting lignocellulose degradation during GWC (green waste composting). This feasibility was studied in a laboratory scale experiment, using three lignocellulolytic microorganisms, isolated from the mature phase of GWC by the dilution plating method. After the feasibility was confirmed, a composite inoculum was developed through the results of the optimization, whose effect was evaluated by comparing it with Phanerochaete chrysosporium and EM (Effective Microorganisms) in a pilot scale experiment of GWC. The use of QROD to finish this optimization was proven feasible, because the p value of the regression equation was less than 0.05 (0.0108), meaning that the quadratic regression model is suitable for describing the relationship between the combination of the three microorganisms and their ability to degrade lignocellulose. Additional proof of this feasibility is that the composite inoculum in the quadratic regression orthogonal experiment demonstrated lignocellulose degradation ability similar to the GWC experiment. Although the lignin degradation ability of the composite inoculum did not surpass Phanerochaete chrysosporium, it was stronger than EM. Meanwhile, cellulose degradation ability and humus synthesis ability of the composite inoculum were stronger than for Phanerochaete chrysosporium and were close to EM. It is hard to tell which inoculum is the best since each inoculum had advantages in different aspects, while the composite inoculum still showed a considerable effect of lignocellulose degradation during GWC.

Biodegradation of Azure-B dye by Serratia liquefaciens and its validation by phytotoxicity, genotoxicity and cytotoxicity studies

The azo dyes in textile industry are a major source of environmental pollution and cause serious threat to aquatic flora and fauna. The present study aims to evaluate the potential of previously isolated lignin peroxidase (LiP) enzyme producing Serratia liquefaciens in degradation of Azure-B (AB) dye. S. liquefaciens showed rapid decolourisation of AB dye (100 mg L^-1) in mineral salt medium (MSM) supplemented with 0.2% glucose and yeast extract, and more than 90% dye decolourisation was observed at 48 h when incubated at 30 °C. Decolourisation conditions were optimized by Response Surface Methodology (RSM) using Box-Behnken Designs (BBD). The dye degradation was further confirmed by ATR-FTIR and GC-MS analysis. Toxicological studies of untreated (UT) and bacterial treated (BT) AB dye solutions were studied by using phytotoxicity, genotoxicity and cytotoxicity endpoints. Phytotoxicity assay using Vigna radiata indicated that bacterial treatment led to detoxification of AB dye. Genotoxicity assay with Allium cepa showed that pure AB dye solutions significantly reduced mitotic index (MI) and induced various chromosomal abnormalities (CAs) like c-mitosis, stickiness, chromosome break, anaphase bridges, vagrant chromosomes and binucleated and micronucleated cell in the root tip cells, whereas, bacterial treated solutions induced relatively less genotoxicity in nature. Improved cell survivability (%) was also noted in kidney cell line (NRK-52E) after S. liquefaciens treated dye solutions than the pure dye solutions. The findings suggest that S. liquefaciens could be a potential bacterium for azo dye degradation, as it is effective in lowering of toxic effects of AB dye.

Lignin-Degrading Abilities of Novel Autochthonous Fungal Isolates Trametes hirsuta F13 and Stereum gausapatum F28

The aim of this research is to isolate and identify fungi with high lignin-degrading abilities that are autochthonous to southern Serbian region. Two novel fungal isolates identified as Trametes hirsuta F13 and Stereum gausapatum F28 were selected to assess their ligninolytic enzyme activities and the efficiency of lignin removal from beech wood sawdust. Obtained results show that both isolates are good sources of industrially valuable enzymes with a potential for application in various biotechnological and industrial processes. Both isolates showed laccase, manganese-dependent peroxidase, and versatile peroxidase activities, while only S. gausapatum F28 had lignin peroxidase activity. This is the first record of the ability of S. gausapatum species to produce lignin peroxidase. T. hirsuta F13 showed higher laccase activity than S. gausapatum F28, while S. gausapatum F28 had higher manganese peroxidase activity. Also, T. hirsuta F13 exhibited much higher laccase activity under submerged cultivation conditions than solid-state cultivation conditions, which is rare for fungi. This is important for industrial processes since the submerged fermentation is a dominant technique in industry. The test of the efficiency of lignin removal showed that both isolates are efficient lignin decomposers. After five weeks of incubation on beech wood sawdust, the total lignin losses were 33.84% with T. hirsuta F13 and 28.8% with S. gausapatum F28.

Peroxidase production and ligninolytic potentials of fresh water bacteria Raoultella ornithinolytica and Ensifer adhaerens

Interest in novel ligninolytic bacteria has remained topical due to, in part, the maneuverability of the bacterial genome. Conversely, the fungal genome lacks the dexterity for similar maneuverability thus, posing challenges in the fungal enzyme yield optimization process. Some impact of this situation includes the inability to commercialize the bio-catalytic process of lignin degradation by fungi. Consequently, this study assessed some fresh water bacteria isolates for ligninolytic and peroxidase properties through the utilization and degradation of model lignin compounds (guaiacol and veratryl alcohol) and the decolourization of selected ligninolytic indicator dyes; Azure B (AZB), Remazol Brilliant Blue R (RBBR) and Congo Red (CR). Bacterial strains with appreciable ligninolytic and peroxidase production potentials were identified through 16S rDNA sequence analysis and the nucleotide sequences deposited in the GenBank. About 5 isolates were positive for the degradation of both guaiacol (GA) and veratryl alcohol (VA) thus, accounting for about 17% of the test isolates. Similarly, AZB, RBBR and CR were respectively decolorized by 3, 2 and 5 bacterial strains thus, accounting for 10%, 7% and 17% of the test isolates. Two of the test bacterial strains were able to decolourize AZB, RBBR and CR respectively and these bacterial strains were identified as Raoultella ornithinolytica OKOH-1 and Ensifer adhaerens NWODO-2 with respective accession numbers as KX640917 and KX640918. Upon quantitation of the peroxidase activities; 5250 ± 0.00 U/L was recorded against Raoultella ornithinolytica OKOH-1 and 5833 ± 0.00 U/L against Ensifer adhaerens NWODO-2. The ligninolytic and dye decolourization properties of Raoultella ornithinolytica OKOH-1 and Ensifer adhaerens NWODO-2 marks for novelty particularly, as dyes with arene substituents were decolourized. Consequently, the potentials for the industrial applicability of these test bacterial strains abound as there is a dearth of information on organisms with such potentials.

Bioinspired versus Enzymatic Oxidation of Some Homologous Thionine Dyes in the Presence of Immobilized Metalloporphyrin Catalysts and Ligninolytic Enzymes

Thionines are recalcitrant and polluting textile dyes presenting various degrees of N-methylation. In this paper, a complete series of homologous thionines was used as the substrates for oxidation in the presence of a bioinspired commercial iron-porphyrin immobilized on to imidazole- and pyridine-functionalized fumed silica, to emulate the active site of ligninolytic peroxidases. The obtained catalytic adducts showed a remarkable ability to catalyze thionine dye oxidation in the presence of different oxidants such as potassium monopersulfate and hydrogen peroxide. Different oxidation patterns were obtained and mechanistically discussed, in comparison with those observed in the presence of some ligninolytic oxidizing enzymes.

Bacterial laccase: recent update on production, properties and industrial applications

Laccases (benzenediol: oxygen oxidoreductase, EC 1.10.3.2) are multi-copper enzymes which catalyze the oxidation of a wide range of phenolic and non-phenolic aromatic compounds in the presence or absence of a mediator. Till date, laccases have mostly been isolated from fungi and plants, whereas laccase from bacteria has not been well studied. Bacterial laccases have several unique properties that are not characteristics of fungal laccases such as stability at high temperature and high pH. Bacteria produce these enzymes either extracellularly or intracellularly and their activity is in a wide range of temperature and pH. It has application in pulp biobleaching, bioremediation, textile dye decolorization, pollutant degradation, biosensors, etc. Hence, comprehensive information including sources, production conditions, characterization, cloning and biotechnological applications is needed for the effective understanding and application of these enzymes at the industrial level. The present review provides exhaustive information of bacterial laccases reported till date.

Differences between two strains of Ceriporiopsis subvermispora on improving the nutritive value of wheat straw for ruminants

AIM

This study evaluated differences between two strains of Ceriporiopsis subvermispora on improving the nutritive value and in vitro degradability of wheat straw.

METHODS AND RESULTS

Wheat straw was treated with the fungi for 7 weeks. Weekly samples were analysed for ergosterol content, in vitro gas production (IVGP), chemical composition and lignin-degrading enzyme activity. Ergosterol data showed CS1 to have a faster initial growth than CS2 and reaching a stationary phase after 3 weeks. The IVGP of CS1-treated wheat straw exceeded the control earlier than CS2 (4 vs 5 weeks). CS1 showed a significantly higher (P < 0·001) selectivity in lignin degradation compared to CS2. Both strains showed peak activity of laccase and manganese peroxidase (MnP) at week 1. CS1 showed a significantly higher (P < 0·001) laccase activity, but lower (P = 0·008) MnP activity compared to CS2.

CONCLUSION

Both CS strains improved the nutritive value of wheat straw. Variation between strains was clearly demonstrated by their growth pattern and enzyme activities.

SIGNIFICANCE AND IMPACT OF THE STUDY

The differences among the two strains provide an opportunity for future selection and breeding programs in improving the extent and selectivity of lignin degradation in agricultural biomass.

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.

Fungal pretreatment of sweet sorghum bagasse with supplements: improvement in lignin degradation, selectivity and enzymatic saccharification

Sweet sorghum bagasse (SSB) from food processing and agricultural industry has attracted the attention for uses in production of biofuel, enzymes and other products. The alteration in lignocellulolytic enzymes by use of supplements in fungal pretreatment of SSB to achieve higher lignin degradation, selectivity value and enzymatic hydrolysis to fermentable sugar was studied. Fungal strain Coriolus versicolor was selected for pretreatment due to high ligninolytic and low cellulolytic enzyme production resulting in high lignin degradation and selectivity value. SSB was pretreated with supplements of veratryl alcohol, syringic acid, catechol, gallic acid, vanillin, guaiacol, CuSO₄ and MnSO₄. The best results were obtained with CuSO₄, gallic acid and syringic acid supplements. CuSO₄ increased the activities of laccase (4.9-fold) and polyphenol oxidase (1.9-fold); gallic acid increased laccase (3.5-fold) and manganese peroxidase (2.5-fold); and syringic acid increased laccase (5.6-fold), lignin peroxidase (13-fold) and arylalcohol oxidase (2.8-fold) resulting in enhanced lignin degradations and selectivity values than the control. Reduced cellulolytic enzyme activities resulted in high cellulose recovery. Enzymatic hydrolysis of pretreated SSB yielded higher sugar due to degradation of lignin and reduced the crystallinity of cellulose. The study showed that supplements could be used to improve the pretreatment process. The results were confirmed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric/differential thermogravimetric analysis of SSB.

Isolation, characterization and transcriptome analysis of a novel Antarctic Aspergillus sydowii strain MS-19 as a potential lignocellulosic enzyme source

Background

With the growing demand for fossil fuels and the severe energy crisis, lignocellulose is widely regarded as a promising cost-effective renewable resource for ethanol production, and the use of lignocellulose residues as raw material is remarkable. Polar organisms have important value in scientific research and development for their novelty, uniqueness and diversity.

Results

In this study, a fungus Aspergillus sydowii MS-19, with the potential for lignocellulose degradation was screened out and isolated from an Antarctic region. The growth profile of Aspergillus sydowii MS-19 was measured, revealing that Aspergillus sydowii MS-19 could utilize lignin as a sole carbon source. Its ability to synthesize low-temperature lignin peroxidase (Lip) and manganese peroxidase (Mnp) enzymes was verified, and the properties of these enzymes were also investigated. High-throughput sequencing was employed to identify and characterize the transcriptome of Aspergillus sydowii MS-19. Carbohydrate-Active Enzymes (CAZyme)-annotated genes in Aspergillus sydowii MS-19 were compared with those in the brown-rot fungus representative species, Postia placenta and Penicillium decumbens. There were 701CAZymes annotated in Aspergillus sydowii MS-19, including 17 cellulases and 19 feruloyl esterases related to lignocellulose-degradation. Remarkably, one sequence annotated as laccase was obtained, which can degrade lignin. Three peroxidase sequences sharing a similar structure with typical lignin peroxidase and manganese peroxidase were also found and annotated as haem-binding peroxidase, glutathione peroxidase and catalase-peroxidase.

Conclusions

In this study, the fungus Aspergillus sydowii MS-19 was isolated and shown to synthesize low-temperature lignin-degrading enzymes: lignin peroxidase (Lip) and manganese peroxidase (Mnp). These findings provide useful information to improve our understanding of low-temperature lignocellulosic enzyme production by polar microorganisms and to facilitate research and applications of the novel Antarctic Aspergillus sydowii strain MS-19 as a potential lignocellulosic enzyme source.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-1028-0) contains supplementary material, which is available to authorized users.

Improvement of selective lignin degradation in fungal pretreatment of sweet sorghum bagasse using synergistic CuSO4-syringic acid supplements

Sweet sorghum bagasse (SSB) generated in large quantities could be hydrolyzed to sugar and then fermented to green fuels. The hydrolysis of SSB polysaccharides interlocked in recalcitrant lignin network is the major problem. Pretreatment of SSB in SSF by using Coriolus versicolor with CuSO₄-syringic acid supplements for effects on production of ligninocellulolytic enzymes, lignin degradation and selectivity values (SV) were studied. C. versicolor was selected based on high ligninolytic and low cellulolytic abilily. Individually, CuSO₄ increased the activities of laccase (4.9 folds) and PPO (1.9 folds); syringic acid increased LiP (13 folds), AAO (2.8 folds) and laccase (5.6 folds) resulting in increased lignin degradation and SVs. Combined syringic acid (4.4 μmol g^-1 SSB) and CuSO₄ (4.4 μmol g^-1 SSB) increased the activities of laccase, LiP, MnP, PPO and AAO by 11.2, 17.6, 2.8, 2.4 and 2.3 folds respectively due to synergistic effect, resulting in maximum lignin degradation 35.9 ± 1.3% (w w^-1) (1.86 fold) and highest SV 3.07 (4.7 fold). Enzymatic hydrolysis of pretreated SSB yielded higher (∼2.2 times) fermentable sugar. Pretreated SSB was characterized by XRD, SEM, FTIR and TGA/DTG analysis to confirm results. It is possible to improve fungal pretreatment of agricultural waste by combination of supplements.