Obtaining fermentable sugars and bioproducts from rice husks by subcritical water hydrolysis in a semi-continuous mode

• Published in: Bioresource technology 2019-01, Vol.272, p.510-520
• Main Authors: Abaide, Ederson R., Ugalde, Gustavo, Di Luccio, Marco, Moreira, Regina de F.P.M., Tres, Marcus V., Zabot, Giovani L., Mazutti, Marcio A.
• Format: Article
• Language: English
• Subjects: Biomass; Biorefinery; Carbohydrate Metabolism; Carbohydrates; Fermentation; Hydrolysis; Kinetics; Levulinic acid; Oryza - metabolism; Reducing sugars; Temperature; TGA; Water - metabolism
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2018.10.075

[Display omitted] •Subcritical water hydrolysis produced up to 18 wt% reducing sugars from rice husks.•Conversion efficiency of 39 g/100 g carbohydrates was obtained at 220 °C.•The maximum content of levulinic acid (2.3 g/L) was obtained at 260 °C.•Dissociation of hemicelluloses is more efficient than dissociation of cellulose. This work aimed at producing fermentable sugars and bioproducts from rice husks by subcritical water hydrolysis at 25 MPa in a semi-continuous mode. The influences of temperature (180 °C; 220 °C; 260 °C) and liquid/solid ratio (7.5 g water/g husks; 15 g water/g husks) on reducing sugar yield (YRS), efficiency (E), kinetic profiles (0–15 min), composition of sugars, inhibitors and organic acids, and physicochemical characteristics of the remaining solid material were evaluated and discussed in the work. The highest YRS (18.0 ± 2.9 g/100 g husks) and E (39.5 ± 1.7 g sugars/100 g carbohydrates) were obtained at 220 °C and 7.5 gwater/g husks. In such condition, the hydrolyzed solutions presented cellobiose (18.0 g/L), xylose 17.7 g/L), arabinose (3.6 g/L), glucose (1.5 g/L), and levulinic acid (0.7 g/L). The fermentable sugars and bioproducts can be applied in several industrial fields, especially for the production of bioethanol and other higher value-added chemical compounds.