Enzymatic digestibility of lignocellulosic wood biomass: Effect of enzyme treatment in supercritical carbon dioxide and biomass pretreatment

Energy and resource intensive mechanical and chemical pretreatment along with the use of hazardous chemicals are major bottlenecks in widespread lignocellulosic biomass utilization. Herein, the study investigated different pretreatment methods on spruce wood namely supercritical CO2 (scCO(2)) pretreatment, ultrasound-assisted alkaline pretreatment, and acetosolv pulping-alkaline hydrogen peroxide bleaching, to enhance the enzymatic digestibility of wood using optimized enzyme cocktail. Also, the effect of scCO(2) pretreatment on enzyme cocktail was investigated after optimizing the concentration and temperature of cellulolytic enzymes. The impact of scCO(2) and ultrasound-assisted alkaline pretreatments of wood were insignificant for the enzymatic digestibility, and acetosolv pulping-alkaline hydrogen peroxide bleaching was the most effective pretreatment that showed the release of total reducing sugar yield (TRS) of similar to 95.0 wt% of total hydrolyzable sugars (THS) in enzymatic hydrolysis. The optimized enzyme cocktail showed higher yield than individual enzymes with degree of synergism 1.34 among the enzymes, and scCO(2) pretreatment of cocktail for 0.5-1.0 h at 10.0-22.0 MPa and 38.0-54.0 degrees C had insignificant effect on the enzyme's primary and global secondary structure of cocktail and its activity.

Automated summary

This study investigated the impact of different pretreatment methods on the enzymatic digestibility of wood and found that acetosolv pulping-alkaline hydrogen peroxide bleaching was the most effective pretreatment. In addition, the optimized enzyme cocktail showed higher yield than individual enzymes and the scCO(2) pretreatment had negligible effect on the structure and activity of the enzyme cocktail.