(501c) Effect of Lignin Content on Hemicellulose Hydrolysis during Liquid Hot Water Pretreatment

Recalcitrance to sugar release is a major limitation for cost-effective industrial conversion of lignocellulosic biomass to biofules. Lignin layers surrounding hydrophilic hemicelluloses and cellulose fibrils in the plant cell walls protect them from the chemical and enzymatic attack. Many work had been reported about the contribution of lignin removal to cellulose accessibility to cellulose, but less to the hemicellulose hydrolysis in the pretreatment process. In this paper, the effect of lignin content on hemicellulose saccharification during liquid hot water pretreatment was investigated. Compared with pure birch xylan, the samples with 50% added kraft lignin showed a yield increase of xylose, xylobiose, xylotriose and xylotetraose with 6,4,2.2 and 1.5 times, respectively, after the liquid hot water pretreatment of 180 °C for 30 min. Similarly, the yield of total xylose decreased with the lignin removal from sugarcane bagasse with peracetic acid. Furthermore, there hybrid energy sorghums with same xylan content but different lignin content were selected to evaluate the effects of lignin content on hemicellulose hydrolysis. The data showed that there was lower initial rate of hemicellulose hydrolysis for the sorghum with high lignin composition. At the same time, the rate of xylose degradation was reduced due to the protection of lignin. All of these results indicated that lignin content was an important factor for the optimization of liquid hot water process and studies on plant cell wall decomposition mechanism.