Green and efficient fractionation of bamboo biomass via synergistic hydrothermal-alkaline deep eutectic solvents pretreatment: Valorization of carbohydrates

The development of green and efficient pretreatment strategies for renewable biomass valorization is required and remains challenging. In this study, a green, efficient, and profitable pretreatment strategy using hydrothermal combined with alkaline deep eutectic solvents (HT-ADESs) was developed for the fractionation and valorization of bamboo biomass. The results demonstrated that HT pretreatment not only selectively valorized hemicellulose into functional xylooligosaccharides (XOS), accounting for 65.9% of hydrolyzed xylan, but also facilitated the subsequent delignification with ADESs. Furthermore, 29% of hemicellulose was recovered from the prehydrolyzate, revealing a branched structure of O-acetyl-4-O-methyl-glucurono-β-(1 → 4)-ᴅ-xylan. Following delignification with choline chloride/monoethanolamine containing 25 wt% peroxide, up to 98.4% glucose yield and 99.2% xylose yield were realized by enzymatic hydrolysis of pretreated residue, which were significantly higher than those of unpretreated bamboo (14.6% and 8.1%, respectively). The incorporation of an appropriate amount of water or peroxide into pure ADES facilitated lignin fractionation and reduced biorefinery costs. Overall, this work presented a promising pathway that could valorize 1 kg of dry bamboo into 490 g of fermentable sugars and 78 g of XOS, accompanied by 54 g of hemicellulose and 200 g of lignin fractions.