Microbial xylanases and their industrial application in pulp and paper biobleaching: a review

Abstract

Xylanases are hydrolytic enzymes which cleave the β-1, 4 backbone of the complex plant cell wall polysaccharide xylan. Xylan is the major hemicellulosic constituent found in soft and hard food. It is the next most abundant renewable polysaccharide after cellulose. Xylanases and associated debranching enzymes produced by a variety of microorganisms including bacteria, actinomycetes, yeast and fungi bring hydrolysis of hemicelluloses. Despite thorough knowledge of microbial xylanolytic systems, further studies are required to achieve a complete understanding of the mechanism of xylan degradation by xylanases produced by microorganisms and their promising use in pulp biobleaching. Cellulase-free xylanases are important in pulp biobleaching as alternatives to the use of toxic chlorinated compounds because of the environmental hazards and diseases caused by the release of the adsorbable organic halogens. In this review, we have focused on the studies of structural composition of xylan in plants, their classification, sources of xylanases, extremophilic xylanases, modes of fermentation for the production of xylanases, factors affecting xylanase production, statistical approaches such as Plackett Burman, Response Surface Methodology to enhance xylanase production, purification, characterization, molecular cloning and expression. Besides this, review has focused on the microbial enzyme complex involved in the complete breakdown of xylan and the studies on xylanase regulation and their potential industrial applications with special reference to pulp biobleaching, which is directly related to increasing pulp brightness and reduction in environmental pollution.

Thermostable enzymes and polysaccharides produced by thermophilic bacteria isolated from Bulgarian hot springs

“…Thermostable and alkaline xylanases are especially useful for the pulp whitening in the paper industry without using environmentally harmful chlorinating agents [22]. The need in effective degradation of the huge plant biomass composed mainly of cellulose and hemicellulose to cheap fermentable sugars could be used for different purposes such as further conversion into ethanol, production of dietary fibers, improving the nutritional value of animal feed, or the production of xylitol that is used as a sweetener in the food industry.…”

Screening of a Soil Bacteria Collection for the Production of Alkali Thermostable Xylanases

“…These enzymes promote the removal of xylan, facilitating the leaching of lignin (Niehaus, Bertoldo, Kahler, & Antranikian, 1999). Therefore, in the paper industry, the use of xylanases represents an important technological improvement because they promote an increase in the bleaching effect without chemical reagents and also decrease the production of pollutants during these processes (Walia, Guleria, Mehta, Chauhan, & Parkash, 2017).…”

Cloning and Over-expression of xynB Gene of Bacillus subtilis subsp. spizizenii W23 into Escherichia coli Origami Host Cells

“…In pulp and paper industries [4,5], candy, and syrup industries [6]. Xylo-oligosacharides products have wide applications in industries, such as in juice-processing and textile industries, bread industry [7].…”