Production of hemicellulases, xylitol, and furan from hemicellulosic hydrolysates using hydrothermal pretreatment

Abstract

Nowadays, manufacturing products (chemicals, fuels, and other value-added products) from renewable sources (such as lignocellulosic biomass) is one of the main challenges which the society has to face in order to achieve a sustainable growth. Lignocellulosic biomass processing in a biorefinery approach is presented as an alternative and promising solution to achieve that by replacing the oil-based market. Hydrothermal treatment is recognized as the first step of a biorefinery since the hemicellulose fraction is easily solubilized and recovered, remaining a spent treated solid composed by cellulose and lignin. Hemicellulose (ramified polysaccharide composed by pentoses and hexoses) presents a great potential to be used as substrate for value-added product production, such as hemicellulases, xylitol, and furan-derived compounds. Hemicellulases are mainly produced from fungi and have application in several industrial sectors, but the high cost of enzymes is the main bottleneck in enzymatic conversion processes. Xylitol can be obtained by chemical or microbial synthesis from xylose. Currently, commercial xylitol has been obtained by chemical processes which generate pollutant degradation products. In the last years, biotechnological processes have received much interest in order to become more competitive and replace chemical synthesis. Moreover, furan-derived compounds are arising as alternative components of renewable fuel due to interesting features (higher heating values than gasoline) and as building blocks for chemical production (e.g., resins, polymers). This chapter will primarily cover the current scenario regarding hemicellulose-derived products, mainly hemicellulases, xylitol, and furan-derived compounds, as well as production processes, industrial applications, and world market focusing on the potential of hydrothermal treatment for the production of these products.