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Category: Microbial Genetics and Molecular Biology; Environmental Microbiology
Fungal Enzymes and Yeasts for Conversion of Plant Biomass to Bioenergy and High-Value Products, Page 1 of 2
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Fungi are now widely used in industrial biotechnology, for example, as production hosts for technical and food and feed processing enzymes, as gene donors for such enzymes, as production hosts for organic acids and cholesterol-lowering drugs (the statins), and as starter cultures and probiotics ( 1 ). Around half of the industrial enzymes used globally are of fungal origin; the other half are of bacterial origin. However, this balance is now moving toward the use of more enzymes from a wider spectrum of families of the fungal kingdom. There are several reasons for this. Fungal enzymes are efficient, compatible, and suitable for industrial processing: they have sufficient protein stability to give the enzyme products an acceptable shelf life; they provide customer solutions, meet regulatory approval demands, and fulfill end user needs.
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A schematic overview of a biorefinery. The product portfolio from biorefineries is not only fuels and chemicals but also includes higher-value products such as food and feed ingredients, cosmetics, skin care, and new functional biomaterials; it is also expected that many types of biorefineries will be developed for improved resource efficiency: the yellow (straw, stover, and wood chips), the green (fresh grass, clover, leaves), the blue (seaweed and fish bycatch and waste), the gray (agroindustrial side streams), and a biorefinery for upgrade of household waste and sludge (the brown biorefinery). Adapted from reference 16 with permission.
A schematic overview of a biorefinery. The product portfolio from biorefineries is not only fuels and chemicals but also includes higher-value products such as food and feed ingredients, cosmetics, skin care, and new functional biomaterials; it is also expected that many types of biorefineries will be developed for improved resource efficiency: the yellow (straw, stover, and wood chips), the green (fresh grass, clover, leaves), the blue (seaweed and fish bycatch and waste), the gray (agroindustrial side streams), and a biorefinery for upgrade of household waste and sludge (the brown biorefinery). Adapted from reference 16 with permission.
(A) Enzymatic breakdown of cellulose polymer includes several glycohydrolases (at least one endoglucanase, at least two cellobiohydrolases, reducing end and non-reducing-end active, and at least one β-glucosidase). Further, the activity of a lytic polysaccharide monooxygenase acts in synergy with the endoglucanase in breaking down the crystallinity of the cellulose polymer. Adapted from reference 24 with permission. (B) Hemicellulose is a very complex, highly branched and substituted polymer. The figure shows seven types of sugar components and lists the seven types of enzymes needed to break the linkages to such sugar moieties. However, enzyme hydrolysis of lignocellulose may not need the presence of all these seven hemicellulases because most of the standard pretreatment procedures will lead to the breakdown of several of the hemicellulose bonds. Adapted from reference 37 with permission.
(A) Enzymatic breakdown of cellulose polymer includes several glycohydrolases (at least one endoglucanase, at least two cellobiohydrolases, reducing end and non-reducing-end active, and at least one β-glucosidase). Further, the activity of a lytic polysaccharide monooxygenase acts in synergy with the endoglucanase in breaking down the crystallinity of the cellulose polymer. Adapted from reference 24 with permission. (B) Hemicellulose is a very complex, highly branched and substituted polymer. The figure shows seven types of sugar components and lists the seven types of enzymes needed to break the linkages to such sugar moieties. However, enzyme hydrolysis of lignocellulose may not need the presence of all these seven hemicellulases because most of the standard pretreatment procedures will lead to the breakdown of several of the hemicellulose bonds. Adapted from reference 37 with permission.
“Fungal Hall of Fame” illustrating the five most important players in industrial lignocellulose biorefinery processing and in research. (A) Aspergillus oryzae, along with (B) Aspergillus niger and Aspergillus nidulans, are the most widely used monocomponent enzyme production organisms. (C) Trichoderma reesei is included due to its exceptional secretion capacity; it is the preferred production host for enzyme blends specifically designed for efficient biomass conversion. (D) Saccharomyces cerevisiae is the organism of choice for production of ethanol from the biomass conversion-derived sugar platform. Pichia pastoris is the expression host most often used for producing laboratory-scale volumes of newly discovered enzymes to facilitate characterization and evaluation of the new enzymes for industrial potentials. (E) Myceliophthora thermophilae, along with another thermophilic fungus, Thermoascus aurantiacus, represents alternatives to production of enzymes by species of Aspergillus. Credits: (A) Courtesy of Reinhard Wilting, Novozymes A/S; (B) from Read ND, in Electron Microscopy of Plant Pathogens (Mendgen K, Lesemann D-E, ed), Springer-Verlag, Berlin, Germany, 1991, with permission; (C) U.S. Department of Energy Office of Science (http://www.jgi.doe.gov/sequencing/why/Treesei.html); (D) Sciencephoto.com; (E) courtesy of Ronald de Vries, CBS-KNAW, Fungal Biodiversity Centre, The Netherlands.
“Fungal Hall of Fame” illustrating the five most important players in industrial lignocellulose biorefinery processing and in research. (A) Aspergillus oryzae, along with (B) Aspergillus niger and Aspergillus nidulans, are the most widely used monocomponent enzyme production organisms. (C) Trichoderma reesei is included due to its exceptional secretion capacity; it is the preferred production host for enzyme blends specifically designed for efficient biomass conversion. (D) Saccharomyces cerevisiae is the organism of choice for production of ethanol from the biomass conversion-derived sugar platform. Pichia pastoris is the expression host most often used for producing laboratory-scale volumes of newly discovered enzymes to facilitate characterization and evaluation of the new enzymes for industrial potentials. (E) Myceliophthora thermophilae, along with another thermophilic fungus, Thermoascus aurantiacus, represents alternatives to production of enzymes by species of Aspergillus. Credits: (A) Courtesy of Reinhard Wilting, Novozymes A/S; (B) from Read ND, in Electron Microscopy of Plant Pathogens (Mendgen K, Lesemann D-E, ed), Springer-Verlag, Berlin, Germany, 1991, with permission; (C) U.S. Department of Energy Office of Science (http://www.jgi.doe.gov/sequencing/why/Treesei.html); (D) Sciencephoto.com; (E) courtesy of Ronald de Vries, CBS-KNAW, Fungal Biodiversity Centre, The Netherlands.
A selection of well-studied lignocellulose degraders across the fungal kingdom
A selection of well-studied lignocellulose degraders across the fungal kingdom