Purification, characterization and gene analysis of exo-cellulase II (Ex-2) from the white rot basidiomycete Irpex lacteus

Characterization of Cellobiohydrolases from Schizophyllum commune KMJ820

A novel cellobiohydrolase (CBH)-generating fungi have been isolated and categorized as Schizophyllum commune KMJ820 based on morphology and rDNA gene sequence. Cellulose powder was used as carbon source, the total enzyme activity was 11.51 U/ml is noted; which is among the highest amounts of CBH-generating microbes studied. CBH have been purified to homogenize, with pursual of serial chromatography using S. commune supernatants and two different CBHs were found; CBH 1 and 2. The filtered CBHs showed greater activity (V max = 51.4 and 20.8 U/mg) in contrast to CBHs from earlier studies. The MW (molecular weights) of S. commune CBH 1 and 2 were verified to be approximately 50 kDa and 150 kDa, respectively, by size exclusion chromatography. Even though CBHs have been evaluated from other sources, but S. commune CBH is prominent in comparison to other CBHs by its high enzyme activity.

Fungi Isolated from Maize (Zea mays L.) Grains and Production of Associated Enzyme Activities

Filamentous fungi produce a great variety of enzymes, and research on their biotechnological potential has recently intensified. The objective of this work was to identify, at the species level, using DNA barcoding, 46 fungal isolates obtained from maize grains with rot symptoms. We also analyzed the production of extracellular amylases, cellulases, proteases and lipases of 33 of those fungal isolates. The enzymatic activities were evaluated by the formation of a clear halo or a white precipitate around the colonies in defined substrate media. The found fungi belong to the genera Talaromyces, Stenocarpella, Penicillium, Phlebiopsis, Cladosporium, Hyphopichia, Epicoccum, Trichoderma, Aspergillus, Irpex, Fusarium, Microdochium, Mucor and Sarocladium. In the genus Fusarium, the species Fusarium verticillioides was predominant and this genus presented the highest diversity, followed by the genera Aspergillus. The best genera for lipase production were Cladosporium and Penicillium; while Cladosporium, Aspergillus and Penicillium were best for cellulase activity; Hyphopichia, Aspergillus and Irpex for amylase activity; and Cladosporium and Sarocladium for proteases activity. In conclusion, a collection of fungi from maize seeds presenting rotten symptoms were obtained, among which exist important producers of hydrolases.

Extra tyrosine in the carbohydrate-binding module of Irpex lacteus Xyn10B enhances its cellulose-binding ability

The xylanase (Xyn10B) that strongly adsorbs on microcrystalline cellulose was isolated from Driselase. The Xyn10B contains a Carbohydrate-binding module family 1 (CBM1) (IrpCBMXyn10B) at N-terminus. The canonical essential aromatic residues required for cellulose binding were conserved in IrpCBMXyn10B; however, its adsorption ability was markedly higher than that typically observed for the CBM1 of an endoglucanase from Trametes hirsuta (ThCBMEG1). An analysis of the CBM-GFP fusion proteins revealed that the binding capacity to cellulose (7.8 μmol/g) and distribution coefficient (2.0 L/μmol) of IrpCBMXyn10B-GFP were twofold higher than those of ThCBMEG1-GFP (3.4 μmol/g and 1.2 L/μmol, respectively), used as a reference structure. Besides the canonical aromatic residues (W24-Y50-Y51) of typical CBM1-containing proteins, IrpCBMXyn10B had an additional aromatic residue (Y52). The mutation of Y52 to Ser (IrpCBMY52S-GFP) reduced these adsorption parameters to 4.4 μmol/g and 1.5 L/μmol, which were similar to those of ThCBMEG1-GFP. These results indicate that Y52 plays a crucial role in strong cellulose binding.

Plant-polysaccharide-degrading enzymes from Basidiomycetes

SUMMARY

Basidiomycete fungi subsist on various types of plant material in diverse environments, from living and dead trees and forest litter to crops and grasses and to decaying plant matter in soils. Due to the variation in their natural carbon sources, basidiomycetes have highly varied plant-polysaccharide-degrading capabilities. This topic is not as well studied for basidiomycetes as for ascomycete fungi, which are the main sources of knowledge on fungal plant polysaccharide degradation. Research on plant-biomass-decaying fungi has focused on isolating enzymes for current and future applications, such as for the production of fuels, the food industry, and waste treatment. More recently, genomic studies of basidiomycete fungi have provided a profound view of the plant-biomass-degrading potential of wood-rotting, litter-decomposing, plant-pathogenic, and ectomycorrhizal (ECM) basidiomycetes. This review summarizes the current knowledge on plant polysaccharide depolymerization by basidiomycete species from diverse habitats. In addition, these data are compared to those for the most broadly studied ascomycete genus, Aspergillus, to provide insight into specific features of basidiomycetes with respect to plant polysaccharide degradation.

Cloning, sequencing and expression analysis of the first cellulase gene encoding cellobiohydrolase 1 from a cold-adaptive Penicillium chrysogenum FS010

A cellobiohydrolase 1 gene (cbh1) was cloned from Penicillium chrysogenum FS010 by a modified thermal asymmetric interlaced polymerase chain reaction (TAIL-PCR). DNA sequencing shows that cbh1 has an open reading frame of 1590 bp, encoding a putative protein of 529 amino acid residues. The deduced amino acid sequence revealed that CBHI has a modular structure with a predicted molecular mass of 56 kDa and consists of a fungal type carbohydrate binding module separated from a catalytic domain by a threonine rich linker region. The putative gene product is homologous to fungal cellobiohydrolases in Family 7 of the glycosyl hydrolases. A novel cbh1 promoter (1.3 kb) was also cloned and sequenced, which contains seven putative binding sites (5'-SYGGRG-3') for the carbon catabolite repressor CRE1. Effect of various carbon sources to the cbh1 transcription of P. chrysogenum was examined by Northern analysis, suggesting that the expression of cbh1 is regulated at transcriptional level. The cbh1 gene in cold-adaptive fungus P. chysogenum was expressed as an active enzyme in Saccharomyces cerevisiae H158. The recombinant CBHI accumulated intracellularly and could not be secreted into the medium.

Role of cellulose-binding domain of exocellulase I from white rot basidiomycete Irpex lacteus

The core fragment (designated P-42), devoid of the cellulose-binding domain (CBD) in the C-terminus and prepared from Irpex lacteus exocellulase I (Ex-1), was isolated by limited proteolysis using papain. Both the hydrolytic activity and binding ability of the isolated P-42 toward insoluble cellulose were lower than those of the native Ex-1, whereas Ex-1 and P-42 showed similar hydrolytic activities toward soluble substrates. These results indicate that the CBD of I. lacteus Ex-1 is the important domain which could enhance hydrolytic activity and binding ability of the enzyme toward insoluble cellulose. In addition, the isolated P-42 was different from the native Ex-1 in terms of enzymatic properties such as pH and temperature stabilities. These differences in stability, with regard to pH and temperature, between P-42 and the native Ex-1 are probably due to the O-linked sugar chains existing in the linker region.

Cloning and characterization of a new exo-cellulase gene, cel3, in Irpex lacteus

A new cellulose-inducible gene (named cel3) was isolated from a strain of the white rot basidiomycete, Irpex lacteus MC-2. The cel3 open reading frame, containing two introns, encodes a polypeptide of 526 amino acids residues with a molecular mass of 55794 Da. Expression of the cel3 gene was induced by various insoluble celluloses and CM-cellulose. Transcription of cel3 was abolished when cells were cultivated in media containing the above cellulosic substrates, but added with glucose, fructose or lactose, while addition of glycerol or mannitol did not affect the cel3 mRNA level. The amino acid sequence of the catalytic domain of the Cel3 protein was homologous to that of fungal exo-type cellulases belonging to family 7 of the glycosyl hydrolases. A phylogenetic study showed that these exo-type cellulases can be clearly separated from family 7 endo-type cellulases.