Physicochemical Characteristics of Fungal Xylanases and their Potential for Biobleaching of Kraft and Non-wood Pulps

Xylanases are enzymes with a wide variety of biotechnological applications, such as in the bioconversion of lignocellulosic materials, improvement of feed digestibility, and bleaching kraft pulps to increase pulp brightness. Many studies have been conducted and published over the years on cellulose pulp bleaching due to the need to search for more sustainable tools and thus reduce environmental pollution. Thus, in this review, we focus on analyzing the biochemical properties of xylanases produced by mesophilic and thermophilic fungi that have been used in the bleaching processes of kraft and non-wood pulps. Eucalyptus kraft pulp is still one of the most used raw materials in the production of pulp and paper, while straw and bagasse are alternative sources of non-wood pulps. Thermophilic fungal xylanases show optimum enzymatic activity at high temperatures and a shorter treatment period when compared to mesophilic xylanases in the bleaching step. However, mesophilic fungal xylanases exhibit a longer period of enzymatic treatment but achieve a satisfactory brightness and kappa number. Hence, these approaches will contribute to future applications of these xylanolytic enzymes in pulp and paper industries.