Bamboo Saccharification by Cellulose Solvent- and Organic Solvent-Based Lignocellulose Fractionation Followed by Ultra Low Enzyme Concentration

Bamboos, giant perennial evergreen grasses, are the fastest growing woody plants and among the highest biomass-producing plants, with an average yearly productivity of up to 39 dry tons per acre in 10-year cycle dedicated plantations. The modified cellulose solvent- (concentrated phosphoric acid) and organic solvent- (95% ethanol) based lignocellulose fractionation (COSLIF) was applied for a naturally-dry moso bamboo sample. The biomass dissolution conditions were 50oC, 1 atm for 60 min. The COSLIF-pretreated bamboo was hydrolyzed very fast at high enzyme loadings. Glucan digestibility was 88.2% at an ultra-low cellulase loading (1 filter paper unit per gram of glucan). The overall glucose and xylose yields were 86.0% and 82.6%, respectively. Scanning electron microscopic images clearly showed that cellulose solvent-based biomass pretreatment efficiently destructed bamboo's fibril structure, resulting in a ~33-fold increase in cellulose accessibility to cellulase (CAC) from 0.27 to 9.14 m2 per gram of biomass. The above results clearly suggest the technological feasibility of producing biofuels from bamboo by using an ultra-low cellulase loading. Cost analysis suggests that a 15-fold decrease in use of costly cellulase would be of importance to decrease overall costs of biomass saccharification when cellulase costs are higher than $0.15 per gallon of cellulosic ethanol.