Biotechnological applications of hemicellulosic derived sugars: State-of-the-art

Hemicellulose is the second most abundant polysaccharide in nature, after cellulose. As a substrate, it is readily available for the production of value-added products with industrial significance, such as ethanol, xylitol, and 2, 3-butanediol. Hemicellulose is a heterogeneous carbohydrate polymer with a xylose-linked backbone connecting to glucose, galactose, mannose, and sugar acids. In general, it represents about 35% of lignocellulosic biomass. It is estimated that the annual production of plant biomass in nature, of which over 90% is lignocellulose, amounts to about 200 × 10⁹ tons per year, where about 8-20 × 10⁹ tons of the primary biomass remains potentially accessible. Hemicellulose, which is generally 20-35% of lignocellulose amounts to nearly ∼70 × 10⁹ tons per year. Continuous efforts by researchers in the last two decades have led the way for the successful conversion of hemicellulose into fermentable constituents by developed candidate pretreatment technologies and engineered hemicellulase enzymes. A major challenge is the isolation of microbes with the ability to ferment a broad range of sugars and withstand fermentative inhibitors that are usually present in hemicellulosic sugar syrup. This chapter aims to explore and review the potential sources of hemicellulose and their degradation into fermentable sugars, as well as advocating their conversion into value-added products like ethanol, xylitol, and 2, 3-butanediol.