This photo is showing five fermenters growing Fusarium solani, which produces cellulases to break down the cellulose in sugar cane waste (bagasse). The name cellulase is used to describe the enzyme material active in depolymerizing cellulose, and is a complex mixture of several different enzymes. The different enzymes present and their relative quantities depend upon the microorganism used for cellulase production and, in some situations, on the enzyme production process. Biomass and waste materials from different sources have different physical properties such as crystallinity, surface area, and different chemical compositions. This is why a variety of different microorganisms must be tested with a particular waste material and why different physical parameters in the fermentation must be tested with each microorganism and waste material complex. Ethanol is the final product of interest in the experiments shown here (31, 150, 151, 152, 230).
Shown is a close-up view of a fermentation of bagasse by the fungus Trichoderma viride. Much research has been done by other groups to find that the Trichoderma spp. cellulase system possesses three major classes of enzymes with different substrates and products. These enzymes have been characterized as endo-B-1,4-glucanase, exo-B-1,4-cellobiohydrolase, and B-glucosidase (cellobiase).
Cellulose waste materials in the fermentation broth undergo enzymatic hydrolysis (breakdown) by the cellulases produced by the fungus. This cellulose waste material is converted into a solution of glucose, hemicellulose, and cellulose. The hemicellulose can be further broken down into D-xylose, D-glucose, D-galactose, D-mannose, L-arabinose, D-glucuronic acid, D-glacturonic acid, 4-O-methyl-D-glucuronic acid, L-rhamnose, and L-fucose with extended fermentation time or by a different fungus (150, 151, 152, 230).
This solution is then fermented (in a separate reactor) into Ethanol by Saccharomyces cerevisiae.
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