Pretreatment of sugarcane bagasse with liquid hot water and aqueous ammonia

Low water consumption operation (LWCO) can reduce the usage of water and energy input for the liquid hot water (LHW) pretreatment of sugarcane bagasse (SB) but causes great negative effects on the saccharification rate of xylose and enzymatic digestibility (ED) of cellulose. Therefore, a combined pretreatment with LHW and aqueous ammonia (LHWAA) was developed. ED of glucan and xylan is enhanced greatly resulted from the removal of hemicellulose and lignin after the LHWAA pretreatment. However, the intriguing results of low lignin removal and ED value were observed at the high reaction temperature of 180 °C for the second step pretreatment of AA. It was proposed that lignin or pseudo-lignin droplet redeposited on the surface of residual solids might play a crucial role in determining the ED, so it is indispensable to make the enzyme access to the cellulose by the step of post-treatment with ultrasonic washing or hot washing. Coupled with the process of post-treatment and enzymatic hydrolysis, a high hemicellulose derived sugars recovery of 75.5% and glucose recovery of 87% was obtained for LHWAA pretreatment.