Microbial xylanase aided biobleaching effect on multiple components of lignocelluloses biomass based pulp and paper: a review

Due to discharge of hazardous organochlorine compounds and absorbable organic halogen compounds in the effluent, the pulp and paper industries are trying to alter the bleaching process to limit the use of chlorine compounds and comply with regulatory, environmental, and market demands. With progress in biotechnology, enzyme technologies can effectively pre-treat lignocellulosic biomass in the pulp and paper making process. Usually, these enzymatic processes reduce the environmental impact of traditional pulp and paper-making processes, lower the overall production cost, and enhance product quality. Microbial xylanases are the potential bio-bleaching candidate due to their renewable, mild operating, highly specific, and eco-friendly nature. Xylanase enhances the efficacy of the bleaching process by breaking the beta-1, 4-glycosidic backbone of the re-precipitated xylan network and removing the trapped lignin from the pulp fibers. Xylanolytic action positively influences the kappa number, hexenuronic acid, chromophore compounds release, pulp crystallinity, morphology and many other attributes of pulp. The present review comprehensively highlights the microbial xylanolytic system, its mechanism, and its application in pulp bioleaching. With the recent development, the paper delineates the xylanase-aided bleaching effects on pulp, paper, and effluent attributes aimed to reduce bleaching chemical use, AOX formation, and energy use in the pulp refining process.