Structural Elucidation Of The Main Components Of Lignocellulosic Biomass And The Enzymatic Hydrolysis Of Rapeseed Straw

We don't need to reiterate the importance and imminence of pollution and energy crisis,which aren't new topics anymore.The eco-friendly utilization of renewable lignocellulose,such as production of biofuels,materials and chemicals,are getting attention around the world.The fractionation of biomass is the most important step among the utilization of lignocellulose and pretreatment is a vital part of fractionation.In this thesis,the effect of hydrothermal,dilute acid pretreatment on the chemical composition,structural features and enzymatic digestibility were comparatively studied.We found that pretreatment and alikali treatment improved enzymatic hydrolysis rate for 5.9 times,up to 93.1%.Additionally,dilute-acid pretreatment achieved the similar effect at much lower temperature,giving a choice for energy efficiency.At the same time,we investigated the lignin collected after alkali treatment and it was found that the lignin collected from rapeseed straw was GS-type lignin.The main linkages between units were?-O-4,?-? and-5 and these linkages broke gradually with the increase of hydrothermal severity.The results indicated that hydrothermal pretreatment at 175? for 45 min with post treatment by 2%NaOH at 100? for 2 h improved lignin yield as well as purity remarkably.Both hydrothermal and dilute-acid pretreatment of the straw has the potential to enable high-yield recovery of lignin for further utilization.Furthermore,eucalypt was submitted to treatment with KOH,LiOH and NaOH to isolating hemicelluloses.We identified the difference of isolating ability among the different alkalis and the difference of hemicelluloses collected from diverse ages.Based on the data we collected,NaOH was the most efficient alkali to isolating the hemicelluloses and the hemicelluloses isolated by KOH was the purest.All hemicelluloses we collected during the experiment had the similar main chain,which were made of xylan,and the similar side chain,which were made of arabinose and glucuronic acid.The hemicelluloses we isolated from E.grandis×E.urophylla mainly consist of 4-O-methylglucurono-D-xylan.