Improving the enzymatic hydrolysis of larch by coupling water pre-extraction with alkaline hydrogen peroxide post-treatment and adding enzyme cocktail

Soluble arabinogalactan (AG) in larch leads to reagent waste during its biorefining using oxidative pretreatment strategies. A two-stage pretreatment of water pre-extraction followed by alkaline hydrogen peroxide (AHP) pretreatment was investigated to more efficiently convert larch cellulose into glucose, while also obtaining a value-added AG product stream. The results showed that water pre-extraction increases the lignin selectivity of both NaOH and H2O2 reagents, translating to improved lignin removal and enzymatic hydrolysis yields. This was found to be related to cellulose accessibility alongside the effective consumption of the reagents. Moreover, the addition of mannanase also significantly enhanced enzymatic digestibility of pretreated solid from 81.0% to 97.7% (4% H2O2 charge and 180 degrees C) when 40 U/g mannanase was supplemented with 20 FPU/g cellulase. In all, it was demonstrated that coupling mannanase with cellulase could improve larch's enzymatic digestibility and overall viability for biorefining processes.