Phosphoric acid-mediated regeneration of sugarcane bagasse cellulose-rich fraction for enzymatic production of water-soluble cellulosic oligomers

Abstract

An integrated strategy was developed to promote conversion of a sugarcane bagasse cellulose-rich fraction into water-soluble cellulosic oligomers (WCOs) through phosphoric acid-mediated regeneration and enzymatic hydrolysis. Alkaline pretreatment on sugarcane bagasse powder increased glucan content from 57.6 to 93.4 g/100 g sample and lowered Klason lignin to 6.1 g/100 g sample. Phosphoric acid-mediated regeneration was subsequently capable of reorganizing the structure of cellulose from sugarcane bagasse, resulting in a decrease of crystallinity from 72.9 to 64.0% and introducing cellulose II-like features. The hydration state of regenerated cellulose strongly influenced hydrolysis performance, as the hydrated form showed significantly higher solubilization (810.4 mg/g sample) and estimated WCO yield (698.1 mg/g sample) than the dried form (448.3 and 370.1 mg/g sample, respectively). Time-course analysis indicated that the estimated WCO yield reached a plateau after 2 h, whereas prolonged hydrolysis mainly increased glucose formation and reduced WCO selectivity, suggesting secondary saccharification. Under this selected condition, the process corresponded to an estimated WCO yield of 17.4 g per 100 g dried bagasse. Positive-ion electrospray ionization mass spectrometry indicated that the hydrolysate showed prominent ions tentatively assignable to cellobiose- and cellotetraose-related species. In animal experiments, a lower starch-induced blood glucose iAUC0-150 min was observed in the high-dose WCO-rich hydrolysate group, and oral administration was associated with changes in fecal Lactobacillus spp. and Bifidobacterium spp. counts. Overall, coupling phosphoric-acid regeneration with preservation of the hydrated state and time-controlled hydrolysis enabled production of WCO-rich hydrolysate from sugarcane bagasse.