cellulases

Cellulases are enzymes that catalyze the hydrolysis of cellulose, the primary structural polymer of plant cell walls. They cleave beta-1,4-glycosidic bonds in cellulose, producing soluble sugars such as glucose and cellobiose. A typical cellulase system comprises three activities: endoglucanases, which cut randomly within the cellulose chain to create new chain ends; exoglucanases (cellobiohydrolases), which release cellobiose units from the chain ends; and beta-glucosidases, which hydrolyze cellobiose and short cello-oligosaccharides to glucose. The activities act synergistically to depolymerize both crystalline and amorphous cellulose.

Sources and production: cellulases are produced by fungi (notably Trichoderma reesei and other Aspergillus species), bacteria (including Clostridium thermocellum and certain Bacillus species), as well as yeasts and some insects. In industrial contexts, fungal enzymes are the most widely used, often produced in submerged or solid-state fermentations and formulated into enzyme cocktails with complementary specificities.

Industrial applications: the most important use is converting lignocellulosic biomass into fermentable sugars for biofuels and biochemicals. Cellulases are also employed in the pulp and paper industry for refining and de-inking, in animal feeds to improve digestibility, and in various detergent and textile processes.

Properties and optimization: cellulase activity depends on pH, temperature, and substrate accessibility. Product inhibition by glucose or cellobiose can reduce efficiency, but thermally stable and engineered enzymes from thermophilic organisms provide improved performance. Modern enzyme cocktails are tailored to feedstock type and processing conditions to maximize hydrolysis efficiency.