Subcritical water hydrolysis of rice husks pretreated with deep eutectic solvent for enhance fermentable sugars production

Rice husks is a residue with relevant amount of cellulose, hemicelluloses and lignin. The potential of deep eutectic solvent was investigated in rice husks pretreatment to delignification and increase in cellulose content. Sequential subcritical water hydrolysis was applied in the best pretreatment condition aiming to produce fermentable sugars. Fourier Transform Infrared Spectroscopy was used in pretreated rice husks to evaluated the increase in cellulose content at different pretreatment time (1, 2, 4 and 6 h), with choline chloride: glycerol and choline chloride: urea. The lignocellulosic composition was determined by thermogravimetric analysis. In the assay at 230 °C with R of 40, the highest yields of reducing sugars were obtained (49.9 ± 2.41 g/100 g biomass) and efficiency (67.91 ± 3.28 g sugars/100 g carbohydrates). [Display omitted] •Aqueous ChCl:GLy DES was highly effective for rice husks pretreatment.•Delignification of 42–46% for all DES pretreatment.•Enrichment in cellulose content of 430% for DES (ChCl:Gly:W20%) pretreatment.•Sequential subcritical water hydrolysis of pretreated rice husks was performed.•High efficiency (67.91 ± 3.28 g sugars/100 g carbohydrates) for pretreated RH submitted to SWH at 230 °C/R-40.