Cellulase is an enzyme which breaks down cellulose to beta-glucose. It is produced mainly by symbiotic bacteria in the ruminating chambers of herbivores. At least two steps in cellulose degradation by microorganisms begin with the preparatory prehydrolytic first step involving an enzyme (C1) which swells and/or hydrates anhydroglucose chains. The second step uses hydrolytic enzymes (Cx) and beta glucosidase (cellobiase). Trichoderma reesei has an extensively studied cellulase enzyme complex. This complex converts crystalline, amorphous, and chemically derived celluloses quantitatively to glucose. Cellulase derived from Trichoderma longbrachiatum is comprised of an enzyme complex consisting of cellulase, a glucosidase, cellobiohydrolase and a glucanase. This complex converts cellulose to beta-dextrins and ultimately to D-glucose. Cellulase is used as a digestive aid, particularly in animals, and for the management of flatulence.