ABSTRACT
Regardless of the type of feedstock, all bioethanol production processes rely on isolating one or more molecular substrates that are used to generate precursors for ethanol-producing reactions. Historically, the production of ethanol has relied almost exclusively on two molecular substrates: starch and sucrose from corn and sugarcane, respectively. In contrast to cornstarch, sucrose is the principal molecular substrate in sugarcane-based bioethanol production. Depending on the source and conditions of formation, cellulose will often form a crystalline structure; however, amorphous cellulose may also form a crystalline structure. Hemicellulose is a branched heteropolymer of hexose sugars, pentose sugars, and sugar acids. The presence of xylans and mannans in lignocellulosic feedstock selection is important when considering feedstock pretreatment and enzyme-mediated systems for substrate deconstruction. All plant-derived cellulosic materials in nature are a combination of cellulose and hemicellulose with various amounts of lignin, pectin, and other molecules contributing to the composite.
