Comparison of liquid hot water (LHW) and high boiling alcohol/water (HBAW) pretreatments for improving enzymatic saccharification of cellulose in bamboo

Liquid hot water (LHW) and high-boiling point alcohol/water (HBAW) pretreatments were compared to improve enzymatic saccharification of cellulose in moso bamboo. When pretreatments were conducted at 200 degrees C for 40 min, HBAW (20% (v/v) 1,4- butanediol (BDO)) induced substrate enzymatic digestibilities (SEDs) at low (5 FPU g(-1) glucan) and high (20 FPU g(-1) glucan) cellulase dosages were 47.1% and 82.3%, which were higher than that of LHW by about 46% and 14%, respectively. The analyses of solid substrates and hydrolysates demonstrated that deposited lignin played a dominating role over other factors including total pore volume, cellulose crystallinity and molecular weight in affecting SED during LHW pretreatment. After optimizing the ratio of BDO to water to be 10% (v/v), a SED and glucose yield of 91.6% and 81.5%, respectively, were obtained by HBAW pretreatment conducted at 200 degrees C for 40 min while cellulase dosage was charged at 20 FPU g(-1) glucan. Under the same conditions but without BDO addition, LHW only resulted in a SED and glucose yield of 72.2% and 62.3%, respectively. Due to no mineral acid addition and low loadings of BDO, HBAW pretreatment has the potential to overcome the drawbacks of LHW pretreatment and become a green, non-expensive and high efficient pretreatment.