Manganese-dependent Peroxidase Research Articles

Biodegradation of pyrene during submerged cultivation of Trametes versicolor

Pyrene is one of the most persistent pollutants belonging to the group of high molecular weight polycyclic aromatic hydrocarbons. Due to the presence of fused benzene rings these compounds are extremely difficult for biodegradation. The white-rot fungi possess remarkably high potential when it comes to the biodegradation of toxic organic substances with aromatic rings due to their unique lignin-degrading enzymatic complex. In the present study, pyrene with concentrations up to 200 ppm was added to the nutrient medium during submerged cultivation of the higher basidiomycete mushroom Trametes versicolor NBIMCC 8939. The experiment continued for 20 days and samples were taken every 5 days. Analysis of the activities of the enzymes laccase and manganese-dependent peroxidase were performed as well as determination of the residual pyrene concertation and identification of the by-products of the degradation process. It was established that the highest pyrene removal was achieved when the lowest initial concentration was introduced to the medium. The strain T. versicolor NBIMCC 8939 was able to biodegrade 12% of the initially introduced 50 ppm pyrene in the medium.

Lignocellulose Degradation Efficiency of Agaricus bisporus Strains Grown on Wheat Straw-Based Compost.

The cultivation of Agaricus bisporus was investigated with two commercial strains, A15 and W192. Nitrogen and lignocellulose were analyzed in absolute amounts based on mass balance to accurately compare the degradation efficiency of the compost, and the correlation between the degradation efficiency and extracellular enzyme activity of the mycelium was analyzed. Lignocellulose utilization efficiency positively correlated with mushroom yield. For the same strain, the compost with high lignocellulose content resulted in high utilization efficiency, which increased the yield of A. bisporus. For the same compost, the lignocellulose utilization efficiency of A15 was higher than that of W192. The activities of manganese-dependent peroxidase and β-glucosidase indicated that W192 may have a higher demand for lignin and cellulose. Therefore, a higher yield of W192 was obtained with high-lignocellulose compost. The metabolism of cellulose and hemicellulose in the mycelial growth stage seemed to be conducive to high mushroom yield.

Ability of marine-derived fungi isolated from polluted saline environment for enzymatic hydrocarbon remediation.

Marine-derived fungi have attracted much attention due to their ability to present a new biosynthetic diversity. About 50 fungal isolates were obtained from Tunisian Mediterranean seawater and then screened for the presence of lignin-peroxidase (LiP), manganese-dependent peroxidase (MnP), and laccase (Lac) activities. The results obtained from both qualitative and quantitative assays showed that four of marine fungi isolates had a high potential to produce lignin-degrading enzymes. They were characterized taxonomically by a molecular method, based on international spacer (ITS) rDNA sequence analysis, as Chaetomium jodhpurense (MH667651.1), Chaetomium maderasense (MH665977.1), Paraconiothyrium variabile (MH667653.1), and Phoma betae (MH667655.1) which have been reported as producers of ligninolytic enzyme in the literature.The enzymatic activities and culture conditions were optimized using a Fractional Factorial design (2 7- 4). Then, fungal strains were incubated with the addition of 1% of crude oil in 50% of seawater for 25days to evaluate their abilities to simultaneously degrade hydrocarbon compounds and to produce ligninolytic enzymes. The strain P. variabile exhibited the highest crude oil degradation rate (48.3%). Significant production of ligninolytic enzymes was recorded during the degradation process, which reached 2730 U/L for the MnP, 410 U/L for LiP, and 168.5 U/L for Lac. The FTIR and GC-MS analysis confirmed that the isolates rapidly biodegrade crude oil under ecological and economic conditions.

The Bacterial Degradation of Lignin—A Review

Microbial degradation of lignin, a natural complex biopolymer, a renewable raw material with a wide range of applications, has been mainly directed at fungal systems, nevertheless, recent studies have proposed the bacterial role in lignin degradation and modification since bacteria possess remarkable environmental adaptability, and various production of enzymes and biochemistry. An occurrence of a high proportion of lignin-degrading genes has been confirmed in actinobacteria and proteobacteria classes by bioinformatics analysis, which points to the probability of undiscovered pathways and enzymes. Because of that, bacterial lignin decomposition might be substantially different from fungal lignin decomposition. Bacteria capable of lignin modification and degradation belong to actinomycetes, some Firmicutes, α-proteobacteria, and γ-proteobacteria. The enzymes responsible for lignin degradation are lignin peroxidase, manganese-dependent peroxidase, versatile peroxidase, dye-decolourizing peroxidase, and laccases. One of the main lignin producers is the pulp and paper manufacturing industry. Lignolytic microorganisms have been identified from diverse habitats, such as in plants, soil, wood, and the gut. Bacterial strains Bacillus, Rhodococcus, Sterptomyces, and Pseudomonas have been reported to have lignin decomposition ability. This review aims to describe the role of bacteria in lignin degradation, bacterial species, and bacterial enzymes included in lignin degradation. Several reports about bacterial species involved in lignin degradation are also highlighted, and the current state of the knowledge on the degradation of lignin from the pulp and paper manufacturing industry are reported.

Ligninolytic characteristics of Pleurotus ostreatus cultivated in cotton stalk media.

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

Construction of CRISPR-Cas9 genome editing platform for white-rot fungus Cerrena unicolor BBP6 and its effects on extracellular ligninolytic enzyme biosynthesis

White-rot fungi (WRF) produce extracellular ligninolytic enzymes such as laccase and manganese-dependent peroxidase (MnP). They have a remarkable potential in degrading a wide range of pollutants including polycyclic aromatic hydrocarbons and synthetic dyes. However, the lack of WRF genetic manipulation methods limits their further applications. Cerrena unicolor BBP6 is a wild-type WRF for laccase and MnP hyper production. This study is the first attempt to develop a genome editing platform for the genus Cerrena sp. based on CRISPR-Cas9 technology. Firstly, the pyrG gene in C. unicolor BBP6 was successfully disrupted and used as an effective screening marker. Subsequently, two genes, LacA and mnp3, which respectively encode a laccase and a MnP protein in strain BBP6, were disrupted. The laccase activity of the LacA mutant strain was reduced by 53.5% compared to the wild-type strain while the MnP activity of the mnp3 mutant strain was reduced by 64.7%. Our study demonstrated that the CRISPR-Cas9 genome-editing platform for C. unicolor BBP6 was successfully established, and it was effective on perturbation of ligninolytic enzyme biosynthesis by this fungus.

Fermenting and Lignin Degradability of a White-Rot Fungus Coriolopsis trogii Using Industrial Lignin as Substrate.

Bio-depolymerized the lignin macromolecules into low molecular lignin-derived aromatic compounds satisfies the requirement for carbon dioxide peaking and is also one of the important ways to realize lignin valorization. Coriolopsis trogii is a kind of less reported lignin-degrading white-rot fungus. The degradability of a self-isolated C. trogii TS01 on industrial lignins, including enzymatic hydrolysis lignin (EHL) and Kraft lignin (KL), was investigated in this paper. The results indicated that EHL could be used as an efficient carbon source to promote the cell growth and ligninolytic enzyme secretion of C. trogii TS01. Compared with using 2% glucose as carbon source, 1% EHL plus 1% glucose would increase the maximum cell dry weight, laccase activity, and manganese-dependent peroxidase activity of C. trogii TS01 by 24.8%, 164.1%, and 200%, respectively. However, the cell growth and ligninolytic enzyme secretion would be significantly inhibited in the case of 1% KL plus 1% glucose used as carbon source. As a result, at the 12th day of fermentation, the degradation rates of EHL and KL were 50.6% and 5.7%, respectively. The UV and FTIR analysis indicated that after been fermented by C. trogii TS01, S-unit content in EHL was decreased by 12.5% but G-unit content was increased by 53.7%. In conclusion, the research of this paper will provide a promising solution for the valorization of enzymatic hydrolysis lignin since the high biodegradation rate of lignin and high activity of ligninolytic enzymes could be achieved simultaneously.

Evaluation of Lignin Degrading Ability and In-silico Analysis and Molecular Docking of Laccase of Schizophyllum commune with Lignin

White-rot fungi have a unique and strong ability to degrade lignin, the most abundant and the strongest natural polymer on earth. The ligninolytic enzymes of these fungi comprise of three groups of oxidative extracellular enzymes mainly, lignin peroxidase (LiP), manganese dependent peroxidase (MnP) and laccase. Fungal laccases are considered to be directly involved with the degradation of lignin. Due to the broad substrate specificity and unique ability of biodegradation, fungal laccases have a great value in industrial and biotechnological applications like bioremediation, detoxification of industrial dyes and treatment of other pollutants. The objectives of this study was to evaluate the lignin degradation ability and laccase producing ability of selected fungal isolates originated from decaying hardwoods of Dimbulagala forest reserve, Sri Lanka and to predict the three-dimensional (3D) structure of laccase from Schizophyllum commune and its binding to lignin using in silicohomology modeling and molecular docking. Ten fungal isolates originated from decaying hardwoods were screened for the lignin degradation ability by using lignin amended malt extract plate assay and laccase producing ability by using guaiacol amended PDA plates. Seven isolates showed lignin degradation ability and five of them were laccase producers. Since S. commune could produce laccase, degrade lignin and laccase protein sequence is available, it was subjected to homology modeling. Homologous templates were identified using BLASTP across Protein Data Bank from NCBI. Laccase from Cerrena sp. was selected as the template for 3D model building of laccase from S. commune using Modeller 10.1. The quality of resulted 3D model of the protein was verified by its energy and stereochemical properties. The unstable regions were selected and remodeled by loop modelling using ModLoop web server. The results of evaluation of the remodeled structure by stereochemical quality and energy was found to be improved and showed that predicted model was of good quality due to the presence of maximum residues in the favored region. Later CB-Dock server was used to perform molecular docking studies using lignin model compounds. The amino acid residues of modeled laccase of S. commune in contact with the lignin based model compounds were identified. These findings help uncovering the lignin degradation mechanisms by S. communelaccases and are useful in biofuel production and bioremediation.
 Keywords: Laccase, Homology modeling, Molecular docking, LigninAcknowledgement: Authors acknowledge the TWAS research grant (18-020 RG/BIO/AS_I), ICGEB research grant (CRP/LKA18-03) and NSF Sri Lanka (RG/2019/BT/03)

Overview of Mycelial Fungi - Lignin Destructors

In this work, the following genuses of mycelial fungi, capable of producing ligninolytic enzymes of various actions, were considered:Penicillium, Aspergillus, Fusariumand Altermaria. Fungi of the genus Aspergilluswere capable of producing laccase, manganese peroxidase and lignin peroxidase in the medium. Penicillium mostly produced laccase. Fusariumproduced laccase, aryl alcohol oxidase, manganesedependent peroxidase, manganese-independent peroxidase and lignin peroxidase. Alternariaproduced laccase, lignin peroxidase and manganese peroxidase. The results demonstrated the possibility of using specific substrates in the study of enzyme activity, as well as the influence of some factors introduced into the medium on the synthesis of enzymes. The auxiliary influence of these fungi on the synthesis of ligninolytic enzymes in symbiosis with otherswas considered.
 Keywords: mycelial fungi, ligninolytic enzymes, Penicillium, Aspergillus, Fusarium, Altermaria

A mechanistic study on electro-Fenton system cooperating with phangerochate chrysosporium to degrade lignin.

The combined catalytic system of Electro-Fenton (E-Fenton) and Phanerochaete chrysosporium (P. chrysosporium) was constructed in liquid medium with additional potential to overcome the limitations of lignin degradation by white rot fungi alone. To further understand the mechanism of synergistic catalysis, we optimized the optimum potential for lignin catalysis by P. chrysosporium and built synergistic versus separate catalyses. After 48 h of incubation, the optimum growth environment and the highest lignin degradation rate (43.8%) of P. chrysosporium were achieved when 4 V was applied. After 96 h, the lignin degradation rate of the cocatalytic system was 62% (E-Fenton catalysis alone 22% and P. chrysosporium catalysis alone 19%), the pH of the growth maintenance system of P. chrysosporium was approximately 3.5, and the lignin peroxidase (LiP) and manganese-dependent peroxidase (MnP) enzyme activities, were significantly better than those of the control. The qPCR results indicated that the expression of both MnP and LiP genes was higher in the cocatalytic system. Meanwhile, FTIR and 2D-HSQC NMR confirmed that the synergistic catalysis was effective in breaking the aromatic functional groups and the side chains of the aliphatic region of lignin. This study showed that the synergistic catalytic process of electro-Fenton and P. chrysosporium was highly efficient in the degradation of lignin. In addition, the synergetic system is simple to operate, economical and green, and has good prospects for industrial application.

ISOLATION, IDENTIFICATION, AND DETECTION OF LIGNINOLYTIC CAPABILITY OF SOME FUNGI ISOLATED FROM SOIL SAMPLES IN EGYPT.

In the present study, twenty-seven fungal species were isolated, purified, and identified from five mixed soil samples collected from Tanta City, Gharbia Governorate, Egypt. The isolated fungal species belonging to nine genera i.e., Aspergillus, Cephalosporium, Fusarium, Penicillium, Botritrichom, Trichoderma, Alternaria, Cladosporium and Scopulariopsis, in addition to two white rot fungi Ganoderma lucidum and Lentinula edodes obtained from Mushroom Laboratory Culture Collection (MLCC), El-Giza, Egypt. The ligninolytic activities of the isolated fungi were evaluated on PDA plates containing 0.02% guaiacol as a chromogenic reagent. Out of the twenty-nine fungal species tested, only three fungi G. lucidum, L. edodes and T. harzianum (isolate 2) showed ligninolytic potential and reddish-brown color zone formed due to guaiacol oxidation. The three positive fungal strains were screened quantitively for Laccase (Lac; E.C. 1.10.3.2), Manganese dependent peroxidase (MnP; E.C. 1.11.1.13), and Lignin peroxidase (LiP; E.C. 1.11.1.14) activities. The highest total ligninase activity was recorded by G. lucidum followed by L. edodes and T. harzianum, respectively.

Bioremediation of polycyclic aromatic hydrocarbons from an aged contaminated agricultural soil using degrading bacteria and soil amendments

The combined effects of degrading bacteria (Paracoccus sp. LXC), humic acid (HA), and soil amendments, including chicken manure, biochar, and wormcast, were investigated through 84 d of incubation in order to improve the remediation of polycyclic aromatic hydrocarbon (PAH) in aged contaminated agricultural soil. PAH concentrations and dissipation kinetics were analyzed, and the biomass and communities of microorganisms and soil enzyme activities were examined to clarify the possible mechanism. The highest removal efficiency of PAHs was 42.1% when treated with Paracoccus sp. LXC combined with biochar and HA. PAH dissipation was consistent with the first-order kinetics model and the half-life of PAHs decreased from 2323.3 d in the natural attenuation to 103–277 d in the amended microcosms. Soil amendments and HA promoted the development of PAH-degrading bacteria and diversity of bacterial communities in soil but not that of fungi. The removal efficiency of PAHs was positively correlated with the density of PAH-degrading bacteria and soil urease (Ure), dehydrogenase (Deh), and manganese-dependent peroxidase (Mnp) activities (r = 0.824–0.941, p < .01). The Paracoccus sp. LXC apparently removed 2–4-ring PAHs, and biochar and wormcast were effective in removing 2–4-ring and 5–6-ring PAHs, respectively. The combined bioremediation strategy using degrading bacteria with soil amendments and HA has high potential for PAH removal in aged contaminated agricultural soil and the possible mechanism was the combination of bioaugmentation with Paracoccus sp. LXC and biostimulation with HA and soil amendments.

Degradation Products of Polychlorinated Biphenyls and Their In Vitro Transformation by Ligninolytic Fungi.

Metabolites of polychlorinated biphenyls (PCBs)—hydroxylated PCBs (OH-PCBs), chlorobenzyl alcohols (CB-OHs), and chlorobenzaldehydes (CB-CHOs)—were incubated in vitro with the extracellular liquid of Pleurotus ostreatus, which contains mainly laccase and low manganese-dependent peroxidase (MnP) activity. The enzymes were able to decrease the amount of most of the tested OH-PCBs by > 80% within 1 h; the removal of more recalcitrant OH-PCBs was greatly enhanced by the addition of the laccase mediator syringaldehyde. Conversely, glutathione substantially hindered the reaction, suggesting that it acted as a laccase inhibitor. Hydroxylated dibenzofuran and chlorobenzoic acid were identified as transformation products of OH-PCBs. The extracellular enzymes also oxidized the CB-OHs to the corresponding CB-CHOs on the order of hours to days; however, the mediated and nonmediated setups exhibited only slight differences, and the participating enzymes could not be determined. When CB-CHOs were used as the substrates, only partial transformation was observed. In an additional experiment, the extracellular liquid of Irpex lacteus, which contains predominantly MnP, was able to efficiently transform CB-CHOs with the aid of glutathione; mono- and di-chloroacetophenones were detected as transformation products. These results demonstrate that extracellular enzymes of ligninolytic fungi can act on a wide range of PCB metabolites, emphasizing their potential for bioremediation.

Coupling azo dye degradation and biodiesel production by manganese-dependent peroxidase producing oleaginous yeasts isolated from wood-feeding termite gut symbionts

BackgroundTextile industry represents one prevalent activity worldwide, generating large amounts of highly contaminated and rich in azo dyes wastewater, with severe effects on natural ecosystems and public health. However, an effective and environmentally friendly treatment method has not yet been implemented, while concurrently, the increasing demand of modern societies for adequate and sustainable energy supply still remains a global challenge. Under this scope, the purpose of the present study was to isolate promising species of yeasts inhabiting wood-feeding termite guts, for combined azo dyes and textile wastewater bioremediation, along with biodiesel production.ResultsThirty-eight yeast strains were isolated, molecularly identified and subsequently tested for desired enzymatic activity, lipid accumulation, and tolerance to lignin-derived metabolites. The most promising species were then used for construction of a novel yeast consortium, which was further evaluated for azo dyes degradation, under various culture conditions, dye levels, as well as upon the addition of heavy metals, different carbon and nitrogen sources, and lastly agro-waste as an inexpensive and environmentally friendly substrate alternative. The novel yeast consortium, NYC-1, which was constructed included the manganese-dependent peroxidase producing oleaginous strains Meyerozyma caribbica, Meyerozyma guilliermondii, Debaryomyces hansenii, and Vanrija humicola, and showed efficient azo dyes decolorization, which was further enhanced depending on the incubation conditions. Furthermore, enzymatic activity, fatty acid profile and biodiesel properties were thoroughly investigated. Lastly, a dye degradation pathway coupled to biodiesel production was proposed, including the formation of phenol-based products, instead of toxic aromatic amines.ConclusionIn total, this study might be the first to explore the application of MnP and lipid-accumulating yeasts for coupling dye degradation and biodiesel production.

An innovative co-fungal treatment to poplar bark sawdust for delignification and polyphenol enrichment

This work aims to demonstrate a new high-efficient way to lignin degradation plus polyphenol enrichment in poplar bark sawdust by a co-fungal treatment with white rot fungi of C. subvermispora, C. cinereus and P. ostreatus in an equal volume-ratio fermentation for three weeks. The results indicated that compared with any one of these fungi, over 50 % lignin-degradation and 6-fold polyphenol enrichment were achieved at the 12th day for the best performance by these mixed-fungi treatments. The polyphenol enrichments from the increasing amount of protocatechuic acid and caffeic acid-3-glucoside were confirmed by HPLC-ESI-QTOF-MS/MS and ATR-FT-IR, which facilitated the lignin-degradation in turn. They were potentially ascribed to an obvious improvement activity of ligninolytic enzyme (laccase, lignin peroxidase and manganese-dependent peroxidase) for the lignin-degradation and β-glycosidase action for flavonoid degradation, respectively. All above-mentioned results will provide a potential protocol for lignin degradation and polyphenol enrichment when the different fungi in co-culture play a role in synergism.

SCREENING, ISOLATION, AND PRODUCTION OF FUNGAL LACCASE FROM SAW MILL SOIL OF OSMANABAD.

The rainforest and wood decaying habitats are the main sources for the several laccase producers, which include plant, bacteria, fungi and actinomycetes. Among these, several fungal species having laccase producing ability, which mainly includes wood rooting fungi that are often associated with lignin peroxidase or manganese dependent peroxidase or both. In view of this, we screened the natural habitats like saw mill soil and nearby places of Osmanabad district of Maharashtra for isolation of potential fungal species having laccase producing abilities. A total 45 fungal strains were isolated and screened for laccase production on solid media like Czapak dox agar medium containing guaiacol, tannic acid, bromophenol blue, and ABTS. Out of that 24 isolates showed positive results and among these S19 was found to be a potent laccase producing ability. The S19 fungus sp. subcultured on Czapak dox agar slant and screened for laccase enzyme production on solid state fermentation using wheat bran. In conclusion, we isolated the most potent laccase producing S19 fungus sp. from local natural habitats. A total 11.35 U/L of laccase enzyme obtained under optimized solid state fermentation. The enzyme may find potential applications in degradation of xenobiotics, decolourization of dyes, pulp and paper industries, depolymerisation of lignin, pigment degradation, and several other industrial processes.

Improvement of lignocellulosic biomass conversion by optimization of fungal ligninolytic enzyme activity and molasses stillage supplementation

Fungal treatment of lignocellulose is an ecologically and economically acceptable method. However, it needs improvement to increase the hydrolysis rate. A novel combination of multiple response optimization of ligninolytic activity of Trametes hirsuta F13 and supplementation of the lignocellulosic substrate (beechwood sawdust) with sugar beet molasses stillage was employed to improve and manage the desired type of fungal ligninolytic activity leading to a significant enhancement of biomass saccharification. Obtained optimal cultivation conditions (molasses stillage concentration, 13%; substrate moisture, 63%; and temperature, 25 °C) provided the desired combination of laccase and manganese-dependent peroxidase activity, and maintained the activities longer and at higher values (51.5 ± 3.5 U/L and 91 ± 4.24 U/L, respectively) than the conditions without molasses stillage (21.5 ± 2.12 U/L and 31.5 ± 4.9 U/L, respectively). Enzyme hydrolysis of the substrate treated for 7 days in the presence of molasses stillage released 20.54 ± 0.80 mg/mL fermentable sugars, and 63.58 ± 1.47 mg/mL from 18-days treated substrate, while sugar concentrations released from the substrates pretreated without the supplementation were 16.84 ± 0.30 mg/mL and 53.63 ± 2.16 mg/mL, respectively. The proposed new approach of the lignocellulose supplementation with sugar beet molasses stillage and manipulation and improvement of fungal ligninolytic activity proved to be a promising solution for the enhancement of lignocellulose bioconversion.

Pretreatment of Grape Stalks by Fungi: Effect on Bioactive Compounds, Fiber Composition, Saccharification Kinetics and Monosaccharides Ratio.

Grape stalks, an inedible lignocellulosic residue from winemaking and agro-industrial grape juice production, can be valorized as a source of bioactive compounds and as feedstock for the saccharification and bioconversion of soluble sugars. Solid-state fermentation (SSF) by six white-rot fungi was applied as pretreatment. Fiber composition, free radical scavenging activity, four ligninolytic, and three hydrolytic enzyme activities were determined. Saccharification kinetics, yield, and productivity were evaluated and complemented with scanning electron microscopy (SEM), high performance liquid chromatography (HPLC) quantification of monosaccharides, and principal component analysis (PCA). After SSF, the biomass exhibited a drastic free radical scavenging activity decrease and the main enzymes produced were manganese-dependent peroxidase and xylanase. Scanning electron microscopy revealed the erosion of cell walls, and PCA exhibited a negative correlation between saccharification, and neutral detergent fiber and acid detergent lignin. Phlebia rufa pretreated biomass gave the highest sugars yield and productivity, representing a nearly three-fold increase compared to untreated samples. Also, monosaccharides quantification revealed that the 1:1 ratio of glucose to the sum of xylose plus galactose changes to the value of 2:1 after pretreatment. In this work, and for the first time, P. rufa proved to be an effective pretreatment of grape stalks for the saccharification and further bioconversion into value-added chemicals. In addition, lignocellulolytic enzymes were also produced through SSF.

Biodegradation of Reactive Orange 16 azo dye by simultaneous action of Pleurotus ostreatus and the yeast Candida zeylanoides.

The purpose was to investigate a simultaneous biodegradation of the recalcitrant monoazo dye Reactive Orange 16 (RO16) in a mixed culture consisting of a biofilm of Pleurotus ostreatus-colonizing polyamide carrier and a suspension of the yeast Candida zeylanoides to see their biological interactions and possible synergistic action during degradation. Decolorization in the mixed culture was more effective than in the fungal monoculture, the respective decolorizations reaching 87.5% and 70% on day 11. The proliferation of yeast was reduced compared with the C. zeylanoides monoculture but enabled the yeast to participate in decolorization. The interaction of P. ostreatus with the yeast resulted in a gradual decrease of fungal manganese-dependent peroxidase (MnP) and laccase activities. Gas chromatography-mass spectrometry (GC-MS) analysis of the degradation products brought evidence that P. ostreatus split the dye molecule asymmetrically to provide 4-(ethenylsulfonyl) benzene whose concentration was much decreased in the mixed culture suggesting its increased metabolization in the presence of the yeast. In contrast, C. zeylanoides split the azo bond symmetrically producing the metabolites 4-(ethenylsulfonyl) aniline and α-hydroxybenzenepropanoic acid. Those metabolites were rapidly degraded in the mixed culture. A novel aspect is represented by the evidence of a mutual cooperative action of the fungal and yeast microorganisms in the mixed culture resulting in rapid decolorization and degradation of the dye.

Biodegradability of Dental Care Antimicrobial Agents Chlorhexidine and Octenidine by Ligninolytic Fungi.

Chlorhexidine (CHX) and octenidine (OCT), antimicrobial compounds used in oral care products (toothpastes and mouthwashes), were recently revealed to interfere with human sex hormone receptor pathways. Experiments employing model organisms—white-rot fungi Irpex lacteus and Pleurotus ostreatus—were carried out in order to investigate the biodegradability of these endocrine-disrupting compounds and the capability of the fungi and their extracellular enzyme apparatuses to biodegrade CHX and OCT. Up to 70% ± 6% of CHX was eliminated in comparison with a heat-killed control after 21 days of in vivo incubation. An additional in vitro experiment confirmed manganese-dependent peroxidase and laccase are partially responsible for the removal of CHX. Up to 48% ± 7% of OCT was removed in the same in vivo experiment, but the strong sorption of OCT on fungal biomass prevented a clear evaluation of the involvement of the fungi or extracellular enzymes. On the other hand, metabolites indicating the enzymatic transformation of both CHX and OCT were detected and their chemical structures were proposed by means of liquid chromatography–mass spectrometry. Complete biodegradation by the ligninolytic fungi was not achieved for any of the studied analytes, which emphasizes their recalcitrant character with low possibility to be removed from the environment.