Fractionation of poplar using hydrothermal and acid hydrotropic pretreatments for co-producing xylooligosaccharides, fermentable sugars, and lignin nanoparticles

Abstract

In the present study, an integrated process involving hydrothermal pretreatment (HP) and acid hydrotropic pretreatment (AHP) was proposed for co-producing high value-added xylooligosaccharides (XOS), fermentable sugars, and lignin nanoparticles (LNPs) from poplar (Populus spp.). Approximately 36.2% of XOS (X2-X6) was obtained from raw xylan after HP at 170 °C for 50 min. Moreover, LNPs with an average size of 44.8 nm were produced from the HP-AHP pretreated poplar, using p-toluenesulfonic acid at a concentration of 55% (w/v) at 90 °C for 120 min. A mild alkaline incubation adopted to reduce the surface lignin of HP-AHP pretreated poplar significantly improved the enzymatic hydrolysis yield from 69.2% to 97.3%. The mass balance results showed that 1000 g of poplar generated 66.4 g of XOS, 468.0 g of fermentable sugars (442.0 g of glucose and 26.0 g of xylose), and 103.5 g of LNPs.