**7. Applications of cellulases**

According to Sajith et al. [87] on the global enzyme market cellulases occupy the third place (i.e., ≈15%) after amylase (≈25%) and protease (≈18%). Cellulases are currently being produced on commercial scale by several industries all over the world and widely used in various industrial applications [128].

#### **7.1 Paper and pulp industries**

Today, 90% of paper pulp is made of wood. Recycling one ton of newsprint and printing or copier paper saves about 1 ton and more than 2 tons of wood respectively [129]. Usually, the industrial process for eradicating wastepaper pollutants involves re-pulping, screening, cleaning, washing and flotation [130]. According to Shrinath et al. [131] the conventional recycling of waste papers is costly and hazardous to the environment due to the use of chemicals (hydrogen peroxide, sodium hydroxide and sodium silicate). Cellulases are mainly used for the pulping and deinking of waste papers. Enzymatic deinking as whole is an environmental friendly process [132]. Cellulase based pulping process is not only energy efficient, environment-friendly but also improve mechanical strength of the final paper product by improving the inter-fiber bonding [133]. When used with hemicellulases, cellulases improve the brightness and quality of the recycled paper [134].

Besides deinking and pulping, cellulases are also used in paper mills for drainage of clogged pipes by dissolving fiber residues [61] and for manufacturing easily biodegradable cardboards, sanitary papers [135].
