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Molecular substrates of ethanol feedstocks
Published in Ruben Michael Ceballos, Bioethanol and Natural Resources, 2017
Although xylans are the major components of hemicellulose, the heterogeneity of hemicelluloses should not be understated. Hemicelluloses are mixtures of polysaccharides and often include other components. Although hardwoods, grasses, and many fruits feature a robust presence of xylans, mannans play a major role in the hemicellulose found in softwoods and plant seed (Wilkie, 1979; Meier and Reid, 1982; Vierhuis et al., 2000; Lundqvist et al., 2003; Gírio et al., 2010). Mannans can be classified as linear mannan (e.g., glucomannan) or heteromannan (i.e., galactoglucomannan [GGM]). Glucomannan are linear chains composed of randomly arranged β-(1,4)-linked d-mannose with β-(1,4)-linked d-glucose. The ratios of mannose and glucose depend on the origin of glucomannan (Timell, 1967; Northcote, 1972; Popa and Spiridon, 1998; Hongshu et al., 2002). Another form of linear mannan called galactomannan (GM) features 1,6-linked α-d-galactopyranosyl side chains along the standard 1,4-linked β-d-mannopyranosyl main chain (Chaubey and Kapoor, 2001; Prajapati et al., 2013).
Glycan-Based Nanocarriers in Drug Delivery
Published in Raj K. Keservani, Anil K. Sharma, Rajesh K. Kesharwani, Drug Delivery Approaches and Nanosystems, 2017
Songul Yasar Yildiz, Merve Erginer, Tuba Demirci, Juergen Hemberger, Ebru Toksoy Oner
Mannan is one of the important members of the hemicellulose family. Mannan is present in four different forms, each having a β-1,4-linked backbone containing mannose (linear mannan) or a combination of glucose and mannose residues (glucomannan) and occasional side chains of α-1,6-linked galactose residues (galactomannan/galactoglucomannan) (Yasar Yildiz and Toksoy Oner, 2014). Its mucoadhesive properties and highly flexible conformation make mannan a highly preferred polymer for cancer targeting nanobased material (Jain et al., 2010). In many studies, mannans with various molecular weight and functional modifications have been used as a drug delivery agent (Apostolopoulos et al., 2006). It is known that like the other glycans, mannans are powerful anticancer agents as they are natural ligands for mannose receptors, which are widely present on dendritic cells (Martin and Jiang, 2010). Budzynska et al. (2007) revealed that mannan-methotrexate conjugate improved antitumor activity significantly when compared with free methotrexate in mouse model of leukemia. Nanoparticles coated with galactomannan were developed and investigated for endocytosis by macrophages, dendritic cells, and liver cells and the results indicated that liver and colon macrophages and mouse brain were targeted easily by mannosylated liposomes (Gupta et al., 2009; Park et al., 2005b).
Structure and Biosynthesis of Hemicelluloses
Published in Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel, Hemicelluloses and Lignin in Biorefineries, 2017
Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel
Mannans are widespread among land plants and are also present in many algal species, some of which completely lack cellulose in their cell walls.24,25 Several varieties of mannan polysaccharides have been characterized. Structurally, each of these polysaccharides contains a β-1,4-linked backbone composed of mannose residues as in mannans or a combination of glucose and mannose residues in a nonrepeating pattern as in glucomannans; both mannans and glucomannans may be substituted with α-1,6-linked galactose side chains as in galactomannans and galactoglucomannans (Figure 4.9). Mannans and glucomannans are often acetylated. They have been much studied in their role as seed storage compounds, but they are found in variable amounts in all cell walls.3
Molecular and biochemical characterizations of a new cold-active and mildly alkaline β-Mannanase from Verrucomicrobiae DG1235
Published in Preparative Biochemistry & Biotechnology, 2021
Huifang Xie, Chun Kin Kingsley Poon, Hanyan Liu, Dan Wang, Jiangke Yang, Zhenggang Han
Hemicelluloses refer to a group of non-cellulosic polysaccharides in plant cell wall and include xylans, mannans, galactans, and arabinans.[1] Mannans are one of the important polysaccharides present in plant seed endosperms and the hemicelluloses of softwood, including homomannans, galactomannans, glucomannans, and galactoglucomannans.[2] Homomannans are linear polymers that are composed of β-1,4-linked mannose residues. Galactomannans, glucomannans, and galactoglucomannans are heteromannans that contain a combination of mannose and glucose residues in the polysaccharide backbone or have side-chain substitutions with α-1,6-linked galactose residues.[2]
Lignocellulose derived functional oligosaccharides: production, properties, and health benefits
Published in Preparative Biochemistry and Biotechnology, 2019
Latika Bhatia, Ashutosh Sharma, Rakesh K. Bachheti, Anuj K. Chandel
Hemicellulose is a non-linear polymer of pentoses (xylose and arabinose), hexoses (mainly mannose glucose and galactose) and gluco-and galacto-uronic acids. Approximately 25–35% of hemicellulose is available in the plant cell wall which can be easily hydrolyzed into fermentable sugars (xylose sugar mainly). In the overall amount of hemicellulose, xylose (25–35%) constitute a primary part in the annual plant while 15–30% in hardwoods, and 7–10% in softwood.[22] Xylan on hydrolysis either by enzymes or acid catalyst yields XOS.[27] Hemicellulose is comprised of different sugars primarily of D-xylose, and other methylated or acetylated sugars. The hemicellulosic fraction of plant cell wall can be easily converted into its monomers and oligosaccharides causing zero- or near-zero waste.[11] Xylobiose, xylotriose, and substituted oligomers of two to four xylosyl residues are the main outcomes of the degradation of xylan. Xylose units having a chain length of 2–10 constitutes XOS, which are touted as non-digestible food ingredients.[28]Figure 2 presents the molecular structure of major oligosaccharides from lignocellulose feedstock. Various physical, physicochemical and enzymatic methods have been applied for the formation of branched arabino-xylooligosaccharides (AXOS) and XOS from hemicellulose.[29] Arabinooligosaccharides (AOS), are another class of oligosaccharides consisting of 1,3 and 1,5 α l–arabinofuranosyl residues. Arabinans, arabinogalactans or arabino xylans are the natural sources of arabinose present in plants cell wall components.[30] Mannan is a major constituent of hemicelluloses. Mannans are present in various forms such as linear mannan, glucomannan, galactomannan, or glucogalactomannan. Mannan is depolymerized into its oligosaccharides by various mannan-catalytic enzymes. For example, β-1,4-D-mannanases cleaves β-(1,4)-linkages into short-chain manno-oligomers.[25]