Study Of The Effect Of Dilute Acid And Sulfite Pretreatment On Hydrolysis Efficiency Of Bagasse

The biorefinery of lignocellulosic biomass plays an important role in reducing energy crisis and global warming. There are four steps including pretreatments, enzymatic hydrolysis, fermentation and rectification. The pretreatment is one of the most essential processes in lignocellulosic biorefinery, since it can overcome the recalcitrance of biomass, which makes lingnocellulose can be degraded to fermentable sugars by cellulase. This study compared effects of traditional dilute acid (DA) pretreatment and sulfite pretreatment to overcome lignocelluloses recalcitrance (SPORL) on enzymatic hydrolysis efficiency of bagasse.1. The chemical components of bagasse before and after preatment were analyzed. The result demonstrated that the two pretreatment methods can remove hemicelluloses of bagasse, besides, SPORL method can increase the acid soluble lignin of SPORL bagasse.Then the hydrolysis efficiency with low enzyme loading (7.5FPU/g dry bagasse) of pretreated bagasse was compared. And the highest hydrolysis efficiencies of SPORL bagasse and holocellulose were 52.66%and 81.92%, while the data for DA pretreated bagasse was 42.20%and 60.89%.2. To explain above phenomenon, XRD, SEM and FTIR were used to analyze changes of crystallinity, microphysical structures and functional groups of bagasse before and after pretreatments.The XRD data revealed that the crystallinty of untreated bagasse was 51.73%, and the crystallinity of DA and SPORL bagasse was 55.20%å'Œ 57.69%respectively.The possible reason for it was that pretreatments destroied amorphous region of bagasse and increased the relative content of crystallinty.The SEM pictures found that both DA and SPORL pretreatments can destroy original ordered structures of bagasse and make bagasse’s surface loose and rough, and the effect of SPORL method was more serious. The data from FTIR revealed that the hydrogen bond of bagasse was exposed after pretreatments, and pretreatments introduced sulfo groups into bagasse.3. The further experiments, including total adsorption and non-specific adsorption of cellulase on pretreated bagasse, ZETA potentials and the content of sulfo groups, demonstrated that the total adsorption of SPORL bagasse was higher than DA bagasse, while its nonspecific adsorption was lower than DA. The possible reason for it was that SPORL pretreatment can sulfonate the lignin, and SPORL lignin had more negative charges, which can largely reduce the non-specific adsorption.4. In the last stage, the feasibility of enzymatic hydrolysis with high substate loading of SPORL bagasse was investigated. It mainly focused on feasibility of different substrate loading, different enzyme loading, fed-batch hydrolysis and solid-liquid. Among these experiments, substrate loading made few differences on hydrolysis efficiency. By contrast, enzyme loading and adding Ca(OH)2 had obvious influnences on enzymatic hydrolysis. In fed-batch experiment, the substrate loading can be increased to 18%and 22%, and the bagasse and holocellulose hydrolysis efficiency were 54.18%,84.29%and 48.75%,75.84%respectively.