Carbocation scavenger assisted acid pretreatment followed by mild alkaline hydrogen peroxide (AHP) treatment for efficient production of fermentable sugars and lignin adsorbents from hardwood biomass

Pretreatment is one of the key steps in lignocellulosic biorefinery. Single stage acid pretreatment is often insufficiently satisfactory to overcome biomass recalcitrance, as the presence of insoluble lignin with repolymerized structure always hinders biomass fractionation and saccharification. In this work, a sequential acid alkali pretreatment was developed to promote biomass fractionation, saccharification and holistic utilization. Results indicated that the addition of 2-naphthol in acid pretreatment enhanced lignin reactivity towards alkali post-treatment. A synergistic effect was observed between 2-naphthol additive and alkali post-treatment in improving biomass saccharification. As a result, up to 90 % of carbohydrates in raw biomass was released and recovered as fermentable sugars after pretreatment and enzymatic hydrolysis. Besides, enzymatic hydrolysis at cellulose loading of 8 % led to a high glucose concentration of 75.51 g/L in enzymatic hydrolysate. Moreover, lignin recovered after alkaline hydrogen peroxide (AHP) treatment and enzymatic hydrolysis both showed great adsorption performance for lead ions, presenting value-added lignin materials. Finally, the mass balance and energy analysis revealed an optimal fractionation of poplar biomass that could achieve an energy recovery of 86 %.

Automated summary

The sequential acid-alkali pretreatment developed in this study showed promising results in promoting biomass fractionation and saccharification. The addition of 2-naphthol in acid pretreatment enhanced lignin reactivity towards alkali post-treatment, resulting in a synergistic effect in improving biomass saccharification. The mass balance and energy analysis revealed an optimal fractionation of poplar biomass that could achieve an energy recovery of 86%, indicating the potential for sustainable utilization of lignocellulosic biomass.