Microbial sources may represent the most economic and cost effective way for getting process apt xylanases
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Explanation:
The plant cell wall is composed of cellulose (35–50%), hemicellulose (20–30%, mainly xylan) and lignin (20–30%). Cellulose and hemicellulose binds with lignin by covalent and non-covalent interactions. Xylan is the second considerable hemicellulosic constituent, having a linear backbone of β-1, 4-linked xyloses and cell wall material of annual plants accounts for 30, 15–30% of hard woods and 7–10% of soft woods. Xylan is a heteropolysaccharide containing O-acetyl, arabinosyl and 4-O-methyl-d-glucuronic acid substituents. It is substituted with l-arabinose, d-galactose, d-mannoses, and glucouronic acid through glysosidic bonds with acetic acid and ferulic acid by ester bonds (Collins et al. 2005; Ahmed et al. 2011). The depolymerisation action of endo-1,4-xylanases (1,4-β-xylan xylanohydrolase; EC 3.2.1.8) and β-d-xylosidase (1,4-β-xylan xylohydrolase; EC 3.2.1.37) results in the change of the polymeric substance into xylooligosaccharides and xylose (Gomez et al. 2008; Juturu and Wu 2014). Xylan proficiently forms a twofold extended ribbon like structure by means of intrachain hydrogen bonding which is stated to be springier than the twofold helix of β-(1–4) cellulose.
A large variety of xylanases produced by microorganisms become a major group of industrial enzymes that are capable to degrade xylan to renewable fuels and chemicals (Hatanaka 2012), in addition to their use in food, paper and pulp industries (Golugiri et al. 2012; Singh et al. 2013). Several microorganisms including bacteria, fungi and actinomycetes have been reported to be readily hydrolyzing xylans by producing 1,4-β-d endoxylanases (E.C. 3.2.18) and β-xylosidases (EC.3.2.1.37). In recent years, there has been growing awareness in applying green biotechnology to bleaching processes to decrease pollution as well as improve the quality of pulp produced. Biobleaching and biopulping processes have been explored frequently over the past 15 years (Zhao et al. 2004; Singh et al. 2013). It has been shown from the already published studies that enzyme (mainly cellulase-free xylanase) pre-bleaching is environment friendly and economically cheap technology; it can decrease the amount of bleaching chemicals required to achieve agreed brightness in succeeding chemical bleaching phase. It has been shown that enzyme pre-treatment improves the dissemination of sodium hydroxide in both hardwoods and softwoods, and enhances conventional pulping of wood chips and pulp uniformity (Woldesenbet et al. 2012). In conventional papermaking process, manufactures use huge amount of chemicals, which have caused hazardous effluent disposal problems (Ayyachamy and Vatsala 2007; Verma and Satyanarayana 2013).