Recent advances and industrial applications of microbial xylanases: A review

Abstract

Xylanase being a hydrolytic enzyme catalyses the hydrolytic breakdown of 1,4-β-D-xylosidic linkages in xylan which is an important constituent of hemicellulose. Xylanases are hemicellulases required for depolymerization of xylans which are the second most bountiful polysaccharide occurring in nature after cellulose having plant origin. A broad range of organisms have been reported to produce xylanases that include several fungi, bacteria, protozoans, crustaceans, marine algae, insects, snails, gastropods, arthropods, several seeds and plants. Filamentous fungi have been documented to be the useful producers of xylanase because of ease of cultivation, extracellular secretion of enzymes, higher yield and industrial aspect. Fungal xylanases from Aspergillus species and Trichoderma species have been widely studied and characterized and are commercially utilized in bakery and food processing industries. Microbial xylanases have been reported to be single-chain glycoproteins having molecular masses usually 8-145 kDa and exhibit maximum activity in temperature range 40-60 °C. Thermostable xylanases are ideally suited for use in industrial applications because of numerous advantages over thermolabile xylanase such as ability to work in broad temperature range, better substrate utilization and ability to tolerate high temperature in processes as well as better shelf life. Xylanases have widespread utilization in diverse industries such as food industry, textile industry and in pulp and paper industry. Xylanases have emerged to be extremely beneficial in terms of enhancing the production of numerous fruitful products. Over the years the advancements in molecular tools and techniques have enabled the better understanding of regulatory mechanisms heading xylanase production, underlying mechanism of action of xylanases as well as more precise knowledge of xylanase gene. Such advancements have paved the way for better utilization of enzymes in a much broader sense in commercial sector. Xylanases have tremendous industrial applications in commercial sector either on their own or by associating with different enzymes in numerous processes like processing of pulp and fibres; saccharification of agricultural, industrial and municipal wastes; flour improvement for bakery products; pretreatment of forage crops and lignocellulosic biomass; as well as an alternate to treating the textile-cellulosic waste with sulphuric acid.