Modified 1,4-butanediol organosolv pretreatment on hardwood and softwood for efficient coproduction of fermentable sugars and lignin antioxidants

In this work, 1,4-butanediol (BDO) organosolv pretreatment was modified with different additives for efficient coproduction of fermentable sugars and lignin antioxidants from hardwood poplar and softwood masson pine. It was found additives more greatly improved pretreatment efficacy of softwood than hardwood. 3-hydroxy-2-naphthoic acid (HNA) addition introduced hydrophilic acid groups to lignin structure, while 2-naphthol-7-sulph-onate (NS) addition promoted lignin removal, both improving cellulose accessibility for enzymatic hydrolysis. Consequently, BDO pretreatment with 90 mM acid and 2-naphthol-7-sulphonate addition achieved near com-plete cellulose hydrolysis (97.98%) and maximized sugar yield of 88.23% from masson pine at 2% cellulose and 20 FPU/g enzyme loading. More importantly, the recovered lignin possessed great antioxidant activity (RSI = 2.48), due to increased phenolic OH groups, reduced aliphatic OH groups and molecular weight. Results indi-cated the modified BDO pretreatment could significantly improve enzymatic saccharification of highly -recalcitrant softwood, while enabling coproduction of high-performance lignin antioxidants for full biomass utilization.