An overview of mannan structure and mannan-degrading enzyme systems

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 beta-mannanase, beta-glucosidase, and beta-mannosidase. Additional enzymes such as acetyl mannan esterase and alpha-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.

Experimental design of response surface methodology used for utilisation of palm kernel cake as solid substrate for optimised production of fungal mannanase

“…From the industrial point of view, economical and efficient conversion of these polymers, especially cellulose and hemicellulose, to their constituent monomer is very important (Moreira and Filho 2008). Hemicellulose is the second most abundant heteropolymer composed of mainly pentoses (xylose, arabinose), hexoses (mannose, glucose, galactose) and sugar acids (Chauhan et al 2012).…”

An endo-β-1,4-mannanase, AkMan, from the common sea hare Aplysia kurodai

“…Mannan is a group of polysaccharides consisting of four different types of mannan, i.e., linear mannan, galactomannan, glucomannan, and galactoglucomannan (Moreira and Filho, 2008). Mannan exists as a structural polysaccharide in cell wall and/or intercellular matrices of both terrestrial and marine plants.…”

“…For example, a linear mannan from a green seaweed Codium fragile is a homopolymer comprised of -1,4-linked D-mannose residues while glucomannan from konjak root is a mixed polymer comprised of D-mannose and D-3 glucose residues. In addition, the main chain of galactomannan such as locust bean gum and tara gum is modified by-1,6-linked D-galactose branches (Moreira and Filho, 2008). Currently, mannan and its degradation products, i.e., mannooligosaccharides, have been attracting attentions of researchers in the field of food and pharmaceutical industries because these poly-and oligosaccharides exhibit various beneficial effects on human health (Moreira and Filho, 2008;Dhawan and Kaur, 2007).…”

“…In addition, the main chain of galactomannan such as locust bean gum and tara gum is modified by-1,6-linked D-galactose branches (Moreira and Filho, 2008). Currently, mannan and its degradation products, i.e., mannooligosaccharides, have been attracting attentions of researchers in the field of food and pharmaceutical industries because these poly-and oligosaccharides exhibit various beneficial effects on human health (Moreira and Filho, 2008;Dhawan and Kaur, 2007). For example, mannan alleviates intestinal disorders as a dietary fiber and mannooligosaccharides improve intestinal microflora conditions as prebiotics.…”

CELLULOSE SYNTHASE-LIKE A2, a Glucomannan Synthase, Is Involved in Maintaining Adherent Mucilage Structure in Arabidopsis Seed

“…Based on the particular chemical composition of the backbone and the side chains, mannan polysaccharides are classified into four types: pure mannan, glucomannan, galactomannan, and galactoglucomannan (Moreira and Filho, 2008;Wang et al, 2012;Pauly et al, 2013). Each of these polysaccharides is composed of a b-1,4-linked backbone containing Man or a combination of Glc and Man residues.…”