Degradation of cellulose by the major endoglucanase produced from the brown-rot fungus Fomitopsis pinicola

Characterization of a novel acidophilic, ethanol tolerant and halophilic GH12 β-1,4-endoglucanase from Trichoderma asperellum ND-1 and its synergistic hydrolysis of lignocellulosic biomass

A novel acidophilic GH5 β-1,4-endoglucanase (TaCel12) from Trichoderma asperellum ND-1 was efficiently expressed in Pichia pastoris (a 1.5-fold increase). Deglycosylated TaCel12 migrated as a single band (26.5 kDa) in SDS-PAGE. TaCel12 was acidophilic with a pH optimum of 4.0 and displayed great pH stability (>80 % activity over pH 3.0-5.0). TaCel12 exhibited considerable activity towards sodium carboxymethyl cellulose and sodium alginate with Vmax values of 197.97 μmol/min/mg and 119.06 μmol/min/mg, respectively. Moreover, TaCel12 maintained >80 % activity in the presence of 20 % ethanol and 4.28 M NaCl. Additionally, Mn2+, Pb2+ and Cu2+ negatively affected TaCel12 activity, while the presence of 5 mM Co2+ significantly increased the enzyme activity. Analysis of action mode revealed that TaCel12 required at least four glucose (cellotetraose) residues for hydrolysis to yield cellobiose and cellotriose. Site-directed mutagenesis results suggested that Glu133 and Glu217 of TaCel12 are crucial catalytic residues, with Asp116 displaying an auxiliary function. Production of soluble sugars from lignocellulose is a crucial step in bioethanol development, and it is noteworthy that TaCel12 could synergistically yield fermentable sugars from corn stover and bagasse, respectively. Thus TaCel12 with excellent properties will be considered a potential biocatalyst for applications in various industries, especially for lignocellulosic biomass conversion.

Simultaneous Hydrodistillation of Healthy Cedrus atlantica Manetti and Infected by Trametes pini and Ungulina officinalis: Effect on Antibacterial Activity Utilizing a Mixture-Design Method

The Atlas cedar belongs to the Pinaceae family of trees and can be found in a crucial resinous mountain forest in Morocco that spans 133,000 hectares. This endemic species is valued for its wood quality and essential oil (EO), which has various biological activities. However, pathogenic fungi, particularly Trametes pini and Ungulina officinalis, frequently attack Atlas cedarwood, causing significant damage and loss of value. This study aims to extract EO from both healthy and infected Atlas cedarwood to promote its valorization and to assess the antibacterial properties of the resulting EOs. The EOs from healthy and sick cedarwood, as well as a combination of these woods, were extracted using hydrodistillation and simultaneous hydrodistillation. Gas chromatography and mass spectrometry were used to examine the chemical compositions of the EOs. In addition, the disk diffusion method and a measurement of the minimum inhibitory concentration were used to assess the EOs' antibacterial activity against two bacterial strains, namely, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The results show that the extraction yields of healthy cedarwood, cedarwood infected by Trametes pini, and cedarwood infected by U. officinalis were 1.43 ± 0.03, 0.56 ± 0.03, and 0.26 ± 0.06%, respectively, Moreover, the antibacterial results showed that neither the healthy nor the diseased cedar oil had any impact on either strain. However, the EOs from some binary mixtures (75:25, 50:50, and 25:75%) of cedarwood infected by Trametes pini and cedarwood infected by U.ngulina officinalis and the mixture of healthy cedarwood and cedarwood infected by the two fungi inhibited the growth of S. aureus with different MIC values. The findings of this research could lead to the development of new products with antibacterial properties, such as natural disinfectants, and reduce the amount of waste generated by the cedar industry.

Expression, characterization, and activity optimization of a novel cellulase from the thermophilic bacteria Cohnella sp. A01

Cellulases are hydrolytic enzymes with wide scientific and industrial applications. We described a novel cellulase, CelC307, from the thermophilic indigenous Cohnella sp. A01. The 3-D structure of the CelC307 was predicted by comparative modeling. Docking of CelC307 with specific inhibitors and molecular dynamic (MD) simulation revealed that these ligands bound in a non-competitive manner. The CelC307 protein was purified and characterized after recombinant expression in Escherichia coli (E. coli) BL21. Using CMC 1% as the substrate, the thermodynamic values were determined as K_m 0.46 mM, k_cat 104.30 × 10^-3 (S^-1), and k_cat/K_m 226.73 (M^-1 S^-1). The CelC307 was optimally active at 40 °C and pH 7.0. The culture condition was optimized for improved CelC307 expression using Plackett-Burman and Box-Behnken design as follows: temperature 20 °C, pH 7.5, and inoculation concentration with an OD₆₀₀ = 1. The endoglucanase activity was positively modulated in the presence of Na⁺, Li⁺, Ca²⁺, 2-mercaptoethanol (2-ME), and glycerol. The thermodynamic parameters calculated for CelC307 confirmed its inherent thermostability. The characterized CelC307 may be a suitable candidate for various biotechnological applications.

Fomitopsis meliae CFA 2, a novel brown rot for endoglucanase: emphasis towards enhanced endoglucanase production by statistical approach

Brown rot basidiomycetes are a principal group of wood-decaying fungi which degrade wood cellulose and hemicellulose by the combination of carbohydrate active enzymes and non-enzymatic oxidation reactions. Very scant information is available on carbohydrate active enzymes of brown rot fungi. In this context, present study focused on the production of cellulolytic–hemicellulolytic enzymes from newly isolated brown rot Fomitopsis meliae CFA 2. Under solid-state fermentation using wheat bran as the substrate Fomitopsis meliae CFA 2 was able to produce a maximum of 1391.12 ± 21.13 U/g of endoglucanase along with other cellulolytic and hemicellulolytic enzymes. Various fermentation parameters were optimised for enhanced production of endoglucanase by employing Plackett-Burman design followed by Box-Behnken design. A well-fitted regression equation with R² value of 98.91% was attained for endoglucanase. The yield of endoglucanase was enhanced by 1.83-fold after executing statistical optimisation of various fermentative parameters. The newly isolated Fomitopsis meliae CFA 2 was found to be a potential producer of endoglucanase. Enzymatic saccharification of alkali-treated wheat straw and rice straw resulted in release of 190.8 and 318.8 mg/g of reducing sugars, respectively.

Purification and characterization of novel, thermostable and non-processive GH5 family endoglucanase from Fomitopsis meliae CFA 2

Endoglucanases from glycoside hydrolase family 5 (GH5) are the key enzymes in degradation of diverse plant polysaccharides. Present study reports purification, characterization and partial sequencing of novel thermostable GH5 family endoglucanase from a newly isolated brown rot fungi Fomitopsis meliae CFA 2. Endoglucanase was purified 34.18 fold with a specific activity of 302.90 U/mg. The molecular weight of the endoglucanase was 37.87 kDa as determined by SDS PAGE. LC MS/MS analysis identified the protein to be a member of GH5_5 family. The temperature and pH optima for endoglucanase activity were 70 °C and 4.8, respectively. The enzyme catalyzed the hydrolysis of carboxymethyl-cellulose with a Km of 12.0 mg/ml, Vmax of 556.58 μmol/min/mg and Kcat of 129.41/sec. The enzyme was stimulated by Zn⁺² and K⁺ metal ions and DTT. Half-life (t_1/2) for endoglucanase was found to be 11.36 h with decimal reduction time (D) of 37.75 h at 70 °C. The activation energy for endoglucanase was found to be 30.76 kJ/mol (50 °C-70 °C). Looking at the results, the endoglucanase from Fomitopsis meliae CFA 2 seems to be a promising thermostable enzyme which may be applicable in applications like biomass hydrolysis.

Evolution of novel wood decay mechanisms in Agaricales revealed by the genome sequences of Fistulina hepatica and Cylindrobasidium torrendii

Wood decay mechanisms in Agaricomycotina have been traditionally separated in two categories termed white and brown rot. Recently the accuracy of such a dichotomy has been questioned. Here, we present the genome sequences of the white-rot fungus Cylindrobasidium torrendii and the brown-rot fungus Fistulina hepatica both members of Agaricales, combining comparative genomics and wood decay experiments. C. torrendii is closely related to the white-rot root pathogen Armillaria mellea, while F. hepatica is related to Schizophyllum commune, which has been reported to cause white rot. Our results suggest that C. torrendii and S. commune are intermediate between white-rot and brown-rot fungi, but at the same time they show characteristics of decay that resembles soft rot. Both species cause weak wood decay and degrade all wood components but leave the middle lamella intact. Their gene content related to lignin degradation is reduced, similar to brown-rot fungi, but both have maintained a rich array of genes related to carbohydrate degradation, similar to white-rot fungi. These characteristics appear to have evolved from white-rot ancestors with stronger ligninolytic ability. F. hepatica shows characteristics of brown rot both in terms of wood decay genes found in its genome and the decay that it causes. However, genes related to cellulose degradation are still present, which is a plesiomorphic characteristic shared with its white-rot ancestors. Four wood degradation-related genes, homologs of which are frequently lost in brown-rot fungi, show signs of pseudogenization in the genome of F. hepatica. These results suggest that transition toward a brown-rot lifestyle could be an ongoing process in F. hepatica. Our results reinforce the idea that wood decay mechanisms are more diverse than initially thought and that the dichotomous separation of wood decay mechanisms in Agaricomycotina into white rot and brown rot should be revisited.

PCR primers to study the diversity of expressed fungal genes encoding lignocellulolytic enzymes in soils using high-throughput sequencing

Plant biomass degradation in soil is one of the key steps of carbon cycling in terrestrial ecosystems. Fungal saprotrophic communities play an essential role in this process by producing hydrolytic enzymes active on the main components of plant organic matter. Open questions in this field regard the diversity of the species involved, the major biochemical pathways implicated and how these are affected by external factors such as litter quality or climate changes. This can be tackled by environmental genomic approaches involving the systematic sequencing of key enzyme-coding gene families using soil-extracted RNA as material. Such an approach necessitates the design and evaluation of gene family-specific PCR primers producing sequence fragments compatible with high-throughput sequencing approaches. In the present study, we developed and evaluated PCR primers for the specific amplification of fungal CAZy Glycoside Hydrolase gene families GH5 (subfamily 5) and GH11 encoding endo-β-1,4-glucanases and endo-β-1,4-xylanases respectively as well as Basidiomycota class II peroxidases, corresponding to the CAZy Auxiliary Activity family 2 (AA2), active on lignin. These primers were experimentally validated using DNA extracted from a wide range of Ascomycota and Basidiomycota species including 27 with sequenced genomes. Along with the published primers for Glycoside Hydrolase GH7 encoding enzymes active on cellulose, the newly design primers were shown to be compatible with the Illumina MiSeq sequencing technology. Sequences obtained from RNA extracted from beech or spruce forest soils showed a high diversity and were uniformly distributed in gene trees featuring the global diversity of these gene families. This high-throughput sequencing approach using several degenerate primers constitutes a robust method, which allows the simultaneous characterization of the diversity of different fungal transcripts involved in plant organic matter degradation and may lead to the discovery of complex patterns in gene expression of soil fungal communities.

Carbohydrate-binding modules of fungal cellulases: occurrence in nature, function, and relevance in industrial biomass conversion

In this review, the present knowledge on the occurrence of cellulases, with a special emphasis on the presence of carbohydrate-binding modules (CBMs) in various fungal strains, has been summarized. The importance of efficient fungal cellulases is growing due to their potential uses in biorefinery processes where lignocellulosic biomasses are converted to platform sugars and further to biofuels and chemicals. Most secreted cellulases studied in detail have a bimodular structure containing an active core domain attached to a CBM. CBMs are traditionally been considered as essential parts in cellulases, especially in cellobiohydrolases. However, presently available genome data indicate that many cellulases lack the binding domains in cellulose-degrading organisms. Recent data also demonstrate that CBMs are not necessary for the action of cellulases and they solely increase the concentration of enzymes on the substrate surfaces. On the other hand, in practical industrial processes where high substrate concentrations with low amounts of water are employed, the enzymes have been shown to act equally efficiently with and without CBM. Furthermore, available kinetic data show that enzymes without CBMs can desorb more readily from the often lignaceous substrates, that is, they are not stuck on the substrates and are thus available for new actions. In this review, the available data on the natural habitats of different wood-degrading organisms (with emphasis on the amount of water present during wood degradation) and occurrence of cellulose-binding domains in their genome have been assessed in order to identify evolutionary advantages for the development of CBM-less cellulases in nature.

Cellulolytic and xylanolytic enzymes from thermophilic Aspergillus terreus RWY

Thermophilic Aspergillus terreus RWY produced cellulases and xylanases in optimal concentrations at 45 °C in solid state fermentation process, though enzyme production was also observed at 50 and 55 °C. Filter paper cellulase (FP), endoglucanase (EG), β-glucosidase (BGL), cellobiohydrolase (CBH), xylanase, β-xylosidase, α-L-arabinofuranosidase and xylan esterase activities for A. terreus RWY at 45 °C in 72 h were 11.3 ± 0.65, 103 ± 6.4, 122.5 ± 8.7, 10.3 ± 0.66, 872 ± 22.5, 22.1 ± 0.75, 126.4 ± 8.4 and 907 ± 15.5 U (g-ds)(-1) , respectively. Enzyme was optimally active at temperatures and pH ranging between 50-60 °C and 4.0-6.0, respectively. The half life (T1/2 ) of 270 and 240 min at 70 and 75 °C, respectively for the enzyme indicates its stability at higher temperatures. The addition of MnCl2 , CoCl2 , and FeCl3 significantly enhanced cellulase activity. Enzyme demonstrated multiplicity by having seven, one and three isoform(s) for EG, CBH and BGL, respectively. Significant production of functionally active consortium of cellulolytic and xylanolytic enzymes from A. terreus RWY makes it a potential candidate in bioprocessing applications.

Optimization of cellulase production by a brown rot fungus Fomitopsis sp. RCK2010 under solid state fermentation

Culture conditions for enhanced cellulase production from a newly isolated brown rot fungus, Fomitopsis sp. RCK2010 were optimized under solid state fermentation. An initial pH of 5.5 and moisture ratio of 1:3.5 (solid:liquid) were found to be optimal for maximum enzyme production. Of the different carbon sources tested wheat bran gave the maximum production of CMCase (71.526 IU/g), FPase (3.268 IU/g), and β-glucosidase (50.696 IU/g). Among the nitrogen sources, urea caused maximum production of CMCase (81.832 IU/g), where as casein and soyabean meal gave the highest FPase (4.682 IU/g) and β-glucosidase (69.083 IU/g) production, respectively. Among amino acids tested glutamic acid gave the highest production for CMCase (84.127I U/g); however 4-hydroxy-l-proline stimulated maximum FPase production (6.762 IU/g). Saccharification of pretreated rice straw and wheat straw by crude enzyme extract from Fomitopsis sp. RCK2010 resulted in release of 157.160 and 214.044 mg/g of reducing sugar, respectively.

Identification and functional analysis of a gene encoding β-glucosidase from the brown-rot basidiomycete Fomitopsis palustris

The brown-rot basidiomycete Fomitopsis palustris is known to degrade crystalline cellulose (Avicel) and produce three major cellulases, exoglucanases, endoglucanases, and β-glucosidases. A novel β-glucosidase designated as Cel3A was identified from F. palustris grown at the expense of Avicel. The deduced amino acid sequence of Cel3A showed high homology with those of other fungal β-glucosidases that belong to glycosyl hydrolase (GH) family 3. The sequence analysis also indicated that Cel3A contains the N- and C-terminal domains of GH family 3 and Asp-209 was conserved as a catalytic nucleophile. The cloned gene was successfully expressed in the yeast Pichia pastoris and the recombinant protein exhibited β-glucosidase activity with cellobiose and some degree of thermostability. Considering the size and sequence of the protein, the β-glucosidase identified in this study is different from the protein purified directly from F. palustris in the previous study. Our results suggest that the fungus possesses at least two β-glucosidase genes.

Characterization of the endoglucanase and glucomannanase activities of a glycoside hydrolase family 45 protein from Penicillium decumbens 114-2

The gene encoding a glycoside hydrolase (GH) family 45 endoglucanase (Cel45A) was cloned from P. decumbens 114-2 and expressed in Pichia pastoris. To our knowledge, this is the first report of characterization of a GH family 45 protein from Penicillium species. The purified recombinant enzyme showed a higher activity on konjac glucomannan (KGM) than on sodium carboxymethyl cellulose (CMC-Na) or phosphoric acid swollen cellulose (PASC). The highest hydrolytic activity was detected at pH5.0 on KGM and pH 3.5 on CMC-Na, indicating the mode of action on the two substrates may be different for Cel45A. The optimum temperatures on the two substrates were both 60 degrees C and about 90% relative activities were retained at 70 degrees C. Products released from PASC and CMC-Na were mainly cellobiose, cellotriose and cellotetraose. The protein with higher glucomannanase activity might help the efficient degradation of lignocellulose by P. decumbens in the natural state.