Genomic and Transcriptomic Insight of Giant Sclerotium Formation of Wood-Decay Fungi

Many fungi form persistent and dormant sclerotia with compact hardened mycelia during unfavorable circumstances. While most of these sclerotia are small in size, Wolfiporia cocos, a wood-decay fungus, grows into giant sclerotia, which are mainly composed of polysaccharides of linear (1→3)-β-D-glucans. To explore the underlying mechanism of converting sophisticated wood polysaccharides for biosynthesis of highly homogenized glucans in W. cocos, we sequenced and assembled the genome of a cultivated W. cocos strain (WCLT) in China. The 62-Mb haploid genome contains 44.2% repeat sequences, of which, 48.0% are transposable elements (TEs). Contrary to the genome of W. cocos from North America, WCLT has independently undergone a partial genome duplication (PGD) event. The large-scale TE insertion and PGD occurrence overlapped with an archeological Pleistocene stage of low oxygen and high temperature, and these stresses might have induced the differences in sclerotium due to geographical distribution. The wood decomposition enzymes, as well as sclerotium-regulator kinases, aquaporins, and highly expanded gene families such as NAD-related families, together with actively expressed 1,3-β-glucan synthase for sclerotium polysaccharides, all have contributed to the sclerotium formation and expansion. This study shall inspire further exploration on how fungi convert wood into simple glucans in the sclerotium of W. cocos.

Antiviral Properties of Water Extracts of Mycelium Inonotus rheades (Pers.) P. Karst. (1882) against the Virus of Tick-Borne Encephalitis Virus in vitro

Background. Tick-borne encephalitis virus is dangerous and widespread pathogen that is transmitted to humans through the bites of hard ticks. Wild fungi, such as xylotrophic basidiomycetes, are widely used in traditional medicine to treat the infectious diseases and are promising natural sources of new antiviral agents. It was previously shown that aqueous extracts from the mycelium of the Inonotus rheades (Pers.) P. Karst. (1882) fungus exhibit significant antiviral activity against tick-borne encephalitis virus, however, the mechanisms of this activity remain unclear.Aim. To analyze the relationship between the virucidal properties of I. rheades extract and the substrate on which the cultivation was carried out.Materials and methods. The mycelium was grown either in a standard liquid medium with wort or on wooden disks from birch. Extracts of water-soluble polysaccharides were prepared from both mycelium samples. The concentration of infectious tick-borne encephalitis virus was determined using the method of titration of plaque-forming components (PFU). Approximately 30 000 PFU of tick-borne encephalitis virus was mixed with an equal volume of corresponding I. rheades extract at concentration of 8 mg/mL and incubated for 30 min at 37 °C. Afterwards, the residual infectivity of tick-borne encephalitis virus was determined using the identical virus sample incubated with sterile water as a reference.Results. It was found that treatment of tick-borne encephalitis virus with extracts from I. rheades mycelium resulted in inhibition of the infectivity of the virus in the cell culture. However, the same strain of I. rheades, grown on medium with wort, did not exhibit antiviral properties.Conclusions. Virucidal substances are likely to be not the main metabolites of the mycelium of I. rheades, but are rather metabolized wood polysaccharides. Further research is needed to more accurately identify the active ingredients and assess their antiviral activity.

Co-production of Xylooligosaccharides and Xylose From Poplar Sawdust by Recombinant Endo-1,4-β-Xylanase and β-Xylosidase Mixture Hydrolysis

As is well-known, endo-1,4-β-xylanase and β-xylosidase are the rate-limiting enzymes in the degradation of xylan (the major hemicellulosic component), main functions of which are cleavaging xylan to release xylooligosaccharides (XOS) and xylose that these two compounds have important application value in fuel, food, and other industries. This study focuses on enzymatic hydrolysis of poplar sawdust xylan for production of XOS and xylose by a GH11 endo-1,4-β-xylanase MxynB-8 and a GH39 β-xylosidase Xln-DT. MxynB-8 showed excellent ability to hydrolyze hemicellulose of broadleaf plants, such as poplar. Under optimized conditions (50°C, pH 6.0, dosage of 500 U/g, substrate concentration of 2 mg/mL), the final XOS yield was 85.5%, and the content of XOS2−3 reached 93.9% after 18 h. The enzymatic efficiency by MxynB-8 based on the poplar sawdust xylan in the raw material was 30.5%. Xln-DT showed excellent xylose/glucose/arabinose tolerance, which is applied as a candidate to apply in degradation of hemicellulose. In addition, the process and enzymatic mode of poplar sawdust xylan with MxynB-8 and Xln-DT were investigated. The results showed that the enzymatic hydrolysis yield of poplar sawdust xylan was improved by adding Xln-DT, and a xylose-rich hydrolysate could be obtained at high purity, with the xylose yield of 89.9%. The enzymatic hydrolysis yield was higher (32.2%) by using MxynB-8 and Xln-DT together. This study provides a deep understanding of double-enzyme synergetic enzymolysis of wood polysaccharides to valuable products.

Manufacture of Platform Chemicals from Pine Wood Polysaccharides in Media Containing Acidic Ionic Liquids

Pinus pinaster wood samples were subjected to chemical processing for manufacturing furans and organic acids from the polysaccharide fractions (cellulose and hemicellulose). The operation was performed in a single reaction stage at 180 or 190 °C, using a microwave reactor. The reaction media contained wood, water, methyl isobutyl ketone, and an acidic ionic liquid, which acted as a catalyst. In media catalyzed with 1-butyl-3-methylimidazolium hydrogen sulfate, up to 60.5% pentosan conversion into furfural was achieved, but the conversions of cellulose and (galacto) glucomannan in levulinic acid were low. Improved results were achieved when AILs bearing a sulfonated alkyl chain were employed as catalysts. In media containing 1-(3-sulfopropyl)-3-methylimidazolium hydrogen sulfate as a catalyst, near quantitative conversion of pentosans into furfural was achieved at a short reaction time (7.5 min), together with 32.8% conversion of hexosans into levulinic acid. Longer reaction times improved the production of organic acids, but resulted in some furfural consumption. A similar reaction pattern was observed in experiments using 1-(3-sulfobutyl)-3-methylimidazolium hydrogen sulfate as a catalyst.

Promotion effect of NP fire retardant pre-treatment on heat-treated poplar wood. Part 2: hygroscopicity, leaching resistance, and thermal stability

In continuation of the previous study concerning the effects of a combined treatment of wood with nitrogen-phosphorus (NP) fire retardant and heat treatment (HT), the hygroscopicity, leachability, thermal stability, Fourier transform-infrared (FT-IR) spectra, and X-ray diffraction (XRD) properties of Populus beijingensis W.Y. Hsu have been investigated. The wood samples were impregnated with 10% NP fire retardant solution and exposed to HTs at 140°C–160°C for 30 min. HT of NP treated wood reduced the moisture absorption and enhanced the leaching resistance of NP and improved the thermal stability. The HT decomposes the NP and the acidity of these degradation products has a dehydration effect on the wood polysaccharides, and the number of hydroxyl groups in wood decreased substantially. The crystallinity index of the NP-impregnated and heat-treated wood also increased. The post low-temperature HT enhanced the fixation of the NP fire retardant and hydrophobicity of the NP-treated wood.

FT-IR imaging microscopy to localise and characterise simultaneous and selective white-rot decay within spruce wood cells

Spruce wood that had been degraded by white-rot fungi (Trametes versicolororCeriporiopsis subvermispora)and suffered mass losses up to 17% was investigated by transmission Fourier transform infrared (FT-IR) imaging microscopy. A significant marker during incipient simultaneous white-rot (T. versicolor) was the cleavage of glycosidic bonds of polysaccharides that preceded their metabolisation. Simultaneous white-rot processes were also characterised by a relative decrease of the overall lignin content and a relative accumulation of wood polysaccharides. No early marker was found for selective white-rot (C. subvermispora) that removes mainly lignin by an oxidative process. This feature was detected only in wood samples exhibiting mass losses higher than 12%. Furthermore, it was shown, that simultaneous and selective white-rot processes were unevenly distributed within the wood samples but quite evenly distributed within single tracheids.

Methylation Analysis as a Tool for Structural Analysis of Wood Polysaccharides

Summary In modern structural analysis of complex mixtures of wood polysaccharides, methylation analysis is still a valuable and powerful tool for linkage analysis. In this paper, methylation analysis is described for the procedure methylation, methanolysis, silylation and GC/MS. The retention time indexes for the partly methylated methyl glycosides of the relevant wood polysaccharides are listed together with the ratios of the isomers of the different structural units. A calculation model for relative molar response factors is suggested based on a published model for FID detection and on experimental data. Tested for oligosaccharides of known structure including xylotetraose, mannotriose and 63, 64-α-D-galactosyl-mannopentaose, the model gives reproducible and sufficiently correct results. The fate of xylose units substituted with 4-O-methyl glucuronic acid at position 2 is investigated with a model compound.