Received: 14 December 2022 Accepted: 20 April 2023 DOI: 10.1002/bab.2469 REVIEW ARTICLE An insight into microbial sources, classification, and industrial applications of xylanases: A rapid review Damanjeet Kaur 1 Amit Joshi 1 Varruchi Sharma 1 Navneet Batra 2 Anil K. Sharma 3 1 Department of Biotechnology, Sri Guru Gobind Singh College, Chandigarh, India 2 Department of Biotechnology, GGDSD College, Chandigarh, India 3 Department of Biotechnology, Maharishi Markandeshwar Engineering College, Maharishi Markandeshwar (deemed to be University), Mullana-Ambala, Haryana, India Correspondence Navneet Batra, Department of Biotechnology, GGDSD College, Sector 32, Chandigarh 160032, India. Email: navneet05@gmail.com Anil K. Sharma, Department of Biotechnology, Maharishi Markandeshwar Engineering College, Maharishi Markandeshwar (deemed to be University), Mullana-Ambala 133207, Haryana, India. Email: anibiotech18@gmail.com Abstract Endo 1,4-β-d-xylanases (EC3.2.1.8) are one of the key lignocellulose hydrolyz- ing enzymes. Xylan, which is present in copious amounts on earth, forms the primary substrate of endo-xylanases, which can unchain the constituent monosaccharides linked via β-1,4-glycosidic bonds from the xylan backbone. Researchers have shown keen interest in the xylanases belonging to glycoside hydrolase families 10 and 11, whereas those placed in other glycoside hydro- lase families are yet to be investigated. Various microbes such as bacteria and fungi harbor these enzymes for the metabolism of their lignocellulose fibers. These microbes can be used as miniature biofactories of xylanase enzymes for a plethora of environmentally benign applications in pulp and paper industry, bio- fuel production, and for improving the quality of food in bread baking and fruit juice industry. This review highlights the potential of microbes in production of xylanase for industrial biotechnology. KEYWORDS hemicellulose, lignocellulosic biomass, xylanases, xylolytic enzymes 1 INTRODUCTION Hemicellulose, lignin, and cellulose are the principal lig- nocellulosic biomass in the cell wall of plants, which are associated with each other by both the covalent and noncovalent bonds. Further, 25%–30% of all the lignocel- lulose of plants is made up of hemicellulose. 1 Besides this, hemicellulose is itself composed of complex het- eropolysaccharide, that is xylan. 2 Xylan is a polymer of β-xylopyranose residues, which are repeatedly joined to each other with the help of β-1,4-glycosidic bonds. 3 These β-xylopyranose residues are further substituted with sim- Abbreviations: AP, alkaline phosphate; SOD, superoxide dismutase. Damanjeet Kaur and Amit Joshi contributed equally to this work. © 2023 International Union of Biochemistry and Molecular Biology, Inc. ple sugars and organic acids. 4 Further, the importance of xylan can be deduced from the fact that it ranks second after cellulose in terms of its global abundance. 5 It occurs naturally both in hardwoods and softwoods. Hence, it can be employed for several biotechnological applications by enzymatically converting it into simpler forms of sugars. 6–8 Although complete depolymerization of xylan requires an alliance of a set of xylolytic enzymes like endo 1,4-β-d- xylanases (EC3.2.1.8), which play a pivotal role in cleaving xylan specifically at 1,4-β-gylcosidic bonds connecting the primary chain of xylopyranose residues. Xylanases belong- ing to glycoside hydrolase (GH) families 10 and 11 have been explored extensively more than those belonging to GH familes 5, 7, 8, and 43. 9,10 Biotechnol Appl Biochem. 2023;1–15. wileyonlinelibrary.com/journal/bab 1