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Genomic insights into the fungal lignocellulolytic system of Myceliophthora thermophila.

Karnaouri A, Topakas E, Antonopoulou I, Christakopoulos P - Front Microbiol (2014)

Bottom Line: The genome of this fungus has been recently sequenced and annotated, allowing systematic examination and identification of enzymes required for the degradation of lignocellulosic biomass.The genomic analysis revealed the existence of an expanded enzymatic repertoire including numerous cellulases, hemicellulases, and enzymes with auxiliary activities, covering the most of the recognized CAZy families.Most of them were predicted to possess a secretion signal and undergo through post-translational glycosylation modifications.

View Article: PubMed Central - PubMed

Affiliation: Biotechnology Laboratory, Department of Synthesis and Development of Industrial Processes, School of Chemical Engineering, National Technical University of Athens Athens, Greece ; Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology Luleå, Sweden.

ABSTRACT
The microbial conversion of solid cellulosic biomass to liquid biofuels may provide a renewable energy source for transportation fuels. Cellulolytic fungi represent a promising group of organisms, as they have evolved complex systems for adaptation to their natural habitat. The filamentous fungus Myceliophthora thermophila constitutes an exceptionally powerful cellulolytic microorganism that synthesizes a complete set of enzymes necessary for the breakdown of plant cell wall. The genome of this fungus has been recently sequenced and annotated, allowing systematic examination and identification of enzymes required for the degradation of lignocellulosic biomass. The genomic analysis revealed the existence of an expanded enzymatic repertoire including numerous cellulases, hemicellulases, and enzymes with auxiliary activities, covering the most of the recognized CAZy families. Most of them were predicted to possess a secretion signal and undergo through post-translational glycosylation modifications. These data offer a better understanding of activities embedded in fungal lignocellulose decomposition mechanisms and suggest that M. thermophila could be made usable as an industrial production host for cellulolytic and hemicellulolytic enzymes.

No MeSH data available.


Related in: MedlinePlus

Distribution of hemicellulolytic enzymes of M. thermophila throughout nine CE families. Family CE4 is comprised of putative proteins with polysaccharide deacetylase activity, CE5 of cutinases and CE8, 12 of pectin esterases. ND (not determined) refers to sequences encoding putative proteins with unknown activity which are not classified to a specific family.
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Figure 3: Distribution of hemicellulolytic enzymes of M. thermophila throughout nine CE families. Family CE4 is comprised of putative proteins with polysaccharide deacetylase activity, CE5 of cutinases and CE8, 12 of pectin esterases. ND (not determined) refers to sequences encoding putative proteins with unknown activity which are not classified to a specific family.

Mentions: Hemicellulose polymers have a much more diverse structure than cellulose and consequently several enzymes are needed to completely degrade the polysaccharide into monosaccharides. Xylan that is the major component of hemicellulose in the plant cell wall, is consisted of a β-D-(1,4)-linked xylopyranosyl backbone, which, depending on the origin, can be substituted with arabinofuranosyl, 4-0-methylglucopyranosyl, feruloyl and acetyl groups (Shibuya and Iwasaki, 1985). Feruloyl groups can form strong networks through peroxidase-catalyzed oxidative coupling forming diferuloyl bridges (Topakas et al., 2007). The main enzymes needed for depolymerization are xylanases, assisted by accessory enzymes such as β-xylosidases and different arabinofuranosidases making the xylan backbone more accessible (Sørgensen et al., 2007). Other accessible enzymes that enhance xylan degradation are acetyl-xylanesterases (Poutanen et al., 1990), ferulic acid esterases (Topakas et al., 2007), and α-glucuronidases (De Vries et al., 1998). M. thermophila's hemicellulase genes are organized in 10 GH families (3, 10, 11, 30, 43, 51, 62, and 67) (Figure 2) and nine carbohydrate esterase (CE) families (1, 3, 4, 5, 8, 9, 12, 15, and 16) (Figure 3). Many of the encoding proteins have been isolated from the WT culture supernatant or expressed in heterologous hosts and finally characterized in terms of specific activity and physicochemical properties. The majority of them are predicted to follow the secretion pathway, while modified with N- and/or O- glucans, comprising a total amount of 66 enzymes that act synergistically for the degradation of hemicellulose.


Genomic insights into the fungal lignocellulolytic system of Myceliophthora thermophila.

Karnaouri A, Topakas E, Antonopoulou I, Christakopoulos P - Front Microbiol (2014)

Distribution of hemicellulolytic enzymes of M. thermophila throughout nine CE families. Family CE4 is comprised of putative proteins with polysaccharide deacetylase activity, CE5 of cutinases and CE8, 12 of pectin esterases. ND (not determined) refers to sequences encoding putative proteins with unknown activity which are not classified to a specific family.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061905&req=5

Figure 3: Distribution of hemicellulolytic enzymes of M. thermophila throughout nine CE families. Family CE4 is comprised of putative proteins with polysaccharide deacetylase activity, CE5 of cutinases and CE8, 12 of pectin esterases. ND (not determined) refers to sequences encoding putative proteins with unknown activity which are not classified to a specific family.
Mentions: Hemicellulose polymers have a much more diverse structure than cellulose and consequently several enzymes are needed to completely degrade the polysaccharide into monosaccharides. Xylan that is the major component of hemicellulose in the plant cell wall, is consisted of a β-D-(1,4)-linked xylopyranosyl backbone, which, depending on the origin, can be substituted with arabinofuranosyl, 4-0-methylglucopyranosyl, feruloyl and acetyl groups (Shibuya and Iwasaki, 1985). Feruloyl groups can form strong networks through peroxidase-catalyzed oxidative coupling forming diferuloyl bridges (Topakas et al., 2007). The main enzymes needed for depolymerization are xylanases, assisted by accessory enzymes such as β-xylosidases and different arabinofuranosidases making the xylan backbone more accessible (Sørgensen et al., 2007). Other accessible enzymes that enhance xylan degradation are acetyl-xylanesterases (Poutanen et al., 1990), ferulic acid esterases (Topakas et al., 2007), and α-glucuronidases (De Vries et al., 1998). M. thermophila's hemicellulase genes are organized in 10 GH families (3, 10, 11, 30, 43, 51, 62, and 67) (Figure 2) and nine carbohydrate esterase (CE) families (1, 3, 4, 5, 8, 9, 12, 15, and 16) (Figure 3). Many of the encoding proteins have been isolated from the WT culture supernatant or expressed in heterologous hosts and finally characterized in terms of specific activity and physicochemical properties. The majority of them are predicted to follow the secretion pathway, while modified with N- and/or O- glucans, comprising a total amount of 66 enzymes that act synergistically for the degradation of hemicellulose.

Bottom Line: The genome of this fungus has been recently sequenced and annotated, allowing systematic examination and identification of enzymes required for the degradation of lignocellulosic biomass.The genomic analysis revealed the existence of an expanded enzymatic repertoire including numerous cellulases, hemicellulases, and enzymes with auxiliary activities, covering the most of the recognized CAZy families.Most of them were predicted to possess a secretion signal and undergo through post-translational glycosylation modifications.

View Article: PubMed Central - PubMed

Affiliation: Biotechnology Laboratory, Department of Synthesis and Development of Industrial Processes, School of Chemical Engineering, National Technical University of Athens Athens, Greece ; Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology Luleå, Sweden.

ABSTRACT
The microbial conversion of solid cellulosic biomass to liquid biofuels may provide a renewable energy source for transportation fuels. Cellulolytic fungi represent a promising group of organisms, as they have evolved complex systems for adaptation to their natural habitat. The filamentous fungus Myceliophthora thermophila constitutes an exceptionally powerful cellulolytic microorganism that synthesizes a complete set of enzymes necessary for the breakdown of plant cell wall. The genome of this fungus has been recently sequenced and annotated, allowing systematic examination and identification of enzymes required for the degradation of lignocellulosic biomass. The genomic analysis revealed the existence of an expanded enzymatic repertoire including numerous cellulases, hemicellulases, and enzymes with auxiliary activities, covering the most of the recognized CAZy families. Most of them were predicted to possess a secretion signal and undergo through post-translational glycosylation modifications. These data offer a better understanding of activities embedded in fungal lignocellulose decomposition mechanisms and suggest that M. thermophila could be made usable as an industrial production host for cellulolytic and hemicellulolytic enzymes.

No MeSH data available.


Related in: MedlinePlus