Chitosan-assisted dilute acid pretreatment with enhanced prehydrolysate fermentability and enzyme digestibility of pretreated substrates.

Primary challenges in enhancing the dilute acid pretreatment of biomass include improving enzyme digestibility of pretreated substrates and efficiently utilizing sugars in the prehydrolysate. This study provides novel evidence indicating that incorporating chitosan as an in situ modifier in the dilute acid pretreatment of poplar notably enhances the fermentability of initially unfermentable prehydrolysate and increases the enzymatic hydrolysis yield of pretreated substrates by 26.83 %. Eliminating 54 % of major carbonyl inhibitors from the prehydrolysate through the application of chitosan enabled S. cerevisiae to produce 8.62 g/L of ethanol from 18.93 g/L of glucose within 24 h. Furthermore, increased cellulose accessibility, coupled with reduced lignin condensation facilitated by chitosan during pretreatment, likely contributed to the enhanced digestibility of the substrates. This innovative enhancement of dilute acid pretreatment, involving the direct incorporation of 4 % (w/w) chitosan, offers a cost-effective strategy to simultaneously address the challenges posed by fermentation inhibitors and the limited enzyme digestibility associated with dilute acid pretreatment across various pretreatment severities.