Xylanases from fungi: properties and industrial applications
TL;DR: There has been much industrial interest in xylan and its hydrolytic enzymatic complex, as a supplement in animal feed, for the manufacture of bread, food and drinks, textiles, bleaching of cellulose pulp, ethanol and xylitol production.
Abstract: Xylan is the principal type of hemicellulose. It is a linear polymer of beta-D-xylopyranosyl units linked by (1-4) glycosidic bonds. In nature, the polysaccharide backbone may be added to 4-O-methyl-alpha-D-glucuronopyranosyl units, acetyl groups, alpha-L-arabinofuranosyl, etc., in variable proportions. An enzymatic complex is responsible for the hydrolysis of xylan, but the main enzymes involved are endo-1,4-beta-xylanase and beta-xylosidase. These enzymes are produced by fungi, bacteria, yeast, marine algae, protozoans, snails, crustaceans, insect, seeds, etc., but the principal commercial source is filamentous fungi. Recently, there has been much industrial interest in xylan and its hydrolytic enzymatic complex, as a supplement in animal feed, for the manufacture of bread, food and drinks, textiles, bleaching of cellulose pulp, ethanol and xylitol production. This review describes some properties of xylan and its metabolism, as well as the biochemical properties of xylanases and their commercial applications.
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TL;DR: In this article, a comprehensive state of the art describing the advancement in recent pretreaments, metabolic engineering approaches with special emphasis on the latest developments in consolidated biomass processing, current global scenario of bioethanol pilot plants and biorefinery concept for the production of biofuels and bioproducts.
1,369 citations
TL;DR: The various hemicelluloses structures present in lignocellulose, the range of pre-treatment and hydrolysis options including the enzymatic ones, and the role of different microbial strains on process integration aiming to reach a meaningful consolidated bioprocessing are reviewed.
1,355 citations
TL;DR: The structure of mannans and some biochemical properties and applications of mannan-degrading enzymes are reported, showing a complex system of sulfated structure.
Abstract: Hemicellulose is a complex group of heterogeneous polymers and represents one of the major sources of renewable organic matter. Mannan is one of the major constituent groups of hemicellulose in the wall of higher plants. It comprises linear or branched polymers derived from sugars such as d-mannose, d-galactose, and d-glucose. The principal component of softwood hemicellulose is glucomannan. Structural studies revealed that the galactosyl side chain hydrogen interacts to the mannan backbone intramolecularly and provides structural stability. Differences in the distribution of d-galactosyl units along the mannan structure are found in galactomannans from different sources. Acetyl groups were identified and distributed irregularly in glucomannan. Some of the mannosyl units of galactoglucomannan are partially substituted by O-acetyl groups. Some unusual structures are found in the mannan family from seaweed, showing a complex system of sulfated structure. Endohydrolases and exohydrolases are involved in the breakdown of the mannan backbone to oligosaccharides or fermentable sugars. The main-chain mannan-degrading enzymes include β-mannanase, β-glucosidase, and β-mannosidase. Additional enzymes such as acetyl mannan esterase and α-galactosidase are required to remove side-chain substituents that are attached at various points on mannan, creating more sites for subsequent enzymatic hydrolysis. Mannan-degrading enzymes have found applications in the pharmaceutical, food, feed, and pulp and paper industries. This review reports the structure of mannans and some biochemical properties and applications of mannan-degrading enzymes.
590 citations
Cites background from "Xylanases from fungi: properties an..."
...Classes of hemicellulose are named according to the main sugar unit, and most of the main-chain sugars on hemicellulose structure are linked together by β-1,4-glycosidic bonds (Polizeli et al. 2005)....
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TL;DR: This mini-review will discuss the enzymes needed for complete degradation of plant polysaccharides and will give an overview of the latest developments concerning fungal carbohydrate-active enzymes and their corresponding families.
Abstract: Enzymatic degradation of plant polysaccharides has many industrial applications, such as within the paper, food, and feed industry and for sustainable production of fuels and chemicals. Cellulose, hemicelluloses, and pectins are the main components of plant cell wall polysaccharides. These polysaccharides are often tightly packed, contain many different sugar residues, and are branched with a diversity of structures. To enable efficient degradation of these polysaccharides, fungi produce an extensive set of carbohydrate-active enzymes. The variety of the enzyme set differs between fungi and often corresponds to the requirements of its habitat. Carbohydrate-active enzymes can be organized in different families based on the amino acid sequence of the structurally related catalytic modules. Fungal enzymes involved in plant polysaccharide degradation are assigned to at least 35 glycoside hydrolase families, three carbohydrate esterase families and six polysaccharide lyase families. This mini-review will discuss the enzymes needed for complete degradation of plant polysaccharides and will give an overview of the latest developments concerning fungal carbohydrate-active enzymes and their corresponding families.
515 citations
Cites background from "Xylanases from fungi: properties an..."
...The fungal β-1,4-endoxylanases belong to GH families 10 and 11 (Polizeli et al. 2005)....
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TL;DR: The present review discusses the recent advancement in enzyme technology for food industries, a comprehensive list of enzymes used in food processing, the microbial source of these enzymes and the wide range of their application are discussed.
Abstract: The use of enzymes or microorganisms in food preparations is an age-old process. With the advancement of technology, novel enzymes with wide range of applications and specificity have been developed and new application areas are still being explored. Microorganisms such as bacteria, yeast and fungi and their enzymes are widely used in several food preparations for improving the taste and texture and they offer huge economic benefits to industries. Microbial enzymes are the preferred source to plants or animals due to several advantages such as easy, cost-effective and consistent production. The present review discusses the recent advancement in enzyme technology for food industries. A comprehensive list of enzymes used in food processing, the microbial source of these enzymes and the wide range of their application are discussed.
394 citations
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TL;DR: This database provides a detailed and comprehensive description of the structural and evolutionary relationships of the proteins of known structure and provides for each entry links to co-ordinates, images of the structure, interactive viewers, sequence data and literature references.
6,603 citations
"Xylanases from fungi: properties an..." refers background in this paper
...The structures of molecules of both families have been determined and compared (Murzin et al. 1995; Sato et al. 1999; Vardakou et al. 2003)....
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TL;DR: On the basis of a comparison of 482 sequences corresponding to 52 EC entries, 45 families, out of which 22 are polyspecific, can now be defined and has been implemented in the SWISS-PROT protein sequence data bank.
Abstract: 301 glycosyl hydrolases and related enzymes corresponding to 39 EC entries of the I.U.B. classification system have been classified into 35 families on the basis of amino-acid-sequence similarities [Henrissat (1991) Biochem. J. 280, 309-316]. Approximately half of the families were found to be monospecific (containing only one EC number), whereas the other half were found to be polyspecific (containing at least two EC numbers). A > 60% increase in sequence data for glycosyl hydrolases (181 additional enzymes or enzyme domains sequences have since become available) allowed us to update the classification not only by the addition of more members to already identified families, but also by the finding of ten new families. On the basis of a comparison of 482 sequences corresponding to 52 EC entries, 45 families, out of which 22 are polyspecific, can now be defined. This classification has been implemented in the SWISS-PROT protein sequence data bank.
2,046 citations
"Xylanases from fungi: properties an..." refers background in this paper
...They basically comprise two families of glycosyl hydrolases, called F and G or 10 and 11 (Henrissat and Bairoch 1993; Sapag et al. 2002)....
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...Other classifications into various families, proposed for the glycosidases, was arranged by Henrissat and Bairoch (1993), and by Törrönen and Rouvinen (1997), as will be described later....
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TL;DR: The adaptation strategies of the extremophilic xylanases isolated to date and the potential industrial applications of these enzymes will also be presented.
Abstract: Xylanases are hydrolytic enzymes which randomly cleave the β 1,4 backbone of the complex plant cell wall polysaccharide xylan. Diverse forms of these enzymes exist, displaying varying folds, mechanisms of action, substrate specificities, hydrolytic activities (yields, rates and products) and physicochemical characteristics. Research has mainly focused on only two of the xylanase containing glycoside hydrolase families, namely families 10 and 11, yet enzymes with xylanase activity belonging to families 5, 7, 8 and 43 have also been identified and studied, albeit to a lesser extent. Driven by industrial demands for enzymes that can operate under process conditions, a number of extremophilic xylanases have been isolated, in particular those from thermophiles, alkaliphiles and acidiphiles, while little attention has been paid to cold-adapted xylanases. Here, the diverse physicochemical and functional characteristics, as well as the folds and mechanisms of action of all six xylanase containing families will be discussed. The adaptation strategies of the extremophilic xylanases isolated to date and the potential industrial applications of these enzymes will also be presented.
1,584 citations
"Xylanases from fungi: properties an..." refers background in this paper
...family 10 more related to family 5, and family 11 more related to family 12 (Collins et al. 2005)....
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...Xylans are hemicelluloses and the second most abundant natural polysaccharide (Collins et al. 2005)....
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...The extensive research of Collins et al. (2005), however, shows that endoglucanases of families 5, 7, 8 and 43 also have some kind of, although less important, activity on xylans....
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...However, these two families of xylanases seem to have evolutionary origins different from other endoglucanases, i.e. family 10 more related to family 5, and family 11 more related to family 12 (Collins et al. 2005)....
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TL;DR: The present article is an overview of the biotechnological state-of-the-art for cellulases and related enzymes.
1,353 citations
"Xylanases from fungi: properties an..." refers background in this paper
...In recent years, the biotechnological use of xylans and xylanases has grown remarkably (Bhat 2000; Aristidou and Pentillä 2000; Subramaniyan and Prema 2000, 2002; Beg et al. 2000, 2001; Techapun et al. 2003)....
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TL;DR: This review will focus on complex xylan structure and the microbial enzyme complex involved in its complete breakdown, studies on xylanase regulation and production and their potential industrial applications, with special reference to biobleaching.
Abstract: Despite an increased knowledge of microbial xylanolytic systems in the past few years, further studies are required to achieve a complete understanding of the mechanism of xylan degradation by microorganisms and their enzymes. The enzyme system used by microbes for the metabolism of xylan is the most important tool for investigating the use of the second most abundant polysaccharide (xylan) in nature. Recent studies on microbial xylanolytic systems have generally focussed on induction of enzyme production under different conditions, purification, characterization, molecular cloning and expression, and use of enzyme predominantly for pulp bleaching. Rationale approaches to achieve these goals require a detailed knowledge of the regulatory mechanism governing enzyme production. This review will focus on complex xylan structure and the microbial enzyme complex involved in its complete breakdown, studies on xylanase regulation and production and their potential industrial applications, with special reference to biobleaching.
1,339 citations
"Xylanases from fungi: properties an..." refers background in this paper
...In a few microorganisms, a cellulosome may be associated with a xylanosome, forming large complexes responsible for the hydrolysis of both cellulose and xylan (Sunna and Antranikian 1997; Beg et al. 2001)....
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...In recent years, the biotechnological use of xylans and xylanases has grown remarkably (Bhat 2000; Aristidou and Pentillä 2000; Subramaniyan and Prema 2000, 2002; Beg et al. 2000, 2001; Techapun et al. 2003)....
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