Studies On Pretreatment And Enzymatic Hydrolysis Of Lignocellulosic Biomass

Dilute acid pretreatment is one of the most effective pretreatment methods for lignocellulosic biomass by degrading hemicellulose and reducing cellulose crystallinity. In this thesis, corn stover was used as feedstock for dilute acid pretreatment and a new dilute acid pretreatment method consuming very minimum water usage was proposed. The effect of solid to liquid ratio (S/L), temperature, retention time, sulphuric acid usage, steam pressure, and feedstock loading on the pretreatment efficiency were investigated. The steam and water usage, the solid and WIS content of the pretreated corn stover, the monomer and oligomer sugars and the inhibitor concentrations in the prehydrolysate and the enzymatic hydrolysis yield of pretreated slurry were measured and calculated. The optimal pretreatment condition was experimentally determined using the Central Composite Design method and response surface analysis at feedstock loading of 50% and 100%, i.e. H2SO4 usage 2.5% at 190℃for 3min. The fermentation performance of the pretreated slurry at the optimal pretreatment condition was also investigated. The comparison of the differences between the two feedstock loadings was also done, as well as different kinds of lignocellulosic biomass from different places at the optimal condition.The effects on enzymatic hydrolysis of waste office paper (WOP) were investigated in the thesis and the WOP utilization with a practical enzymatic hydrolysis method with industrial application potential was provided. It was found that CaCO3 content in WOP was the main reason that reduced the enzymatic hydrolysis efficiency of WOP. Two pretreatment methods, acid washing and acid presoaking, were tested for the removal of CaCO3 from WOP and the efficiency on enhancement of WOP enzymatic hydrolysis, as a result, the presoaking with sulfuric acid (H2SO4) was the most effective way. The presoaking condition parameters were studied carefully and the optimal condition was found, i.e. solid to liquid (S/L) 1:1.5, H2SO4 7%(v/v) at 50℃for 3 hours. The concentration of glucose and cellobiose reached 36.2 g/L and 7.2 g/L respectively, equals to 73.3% cellulose conversion yield in the prolonged enzymatic hydrolysis at the optimal presoaking conditions.The cellulose enzymatic hydrolysis at different solid contents, temperatures, rotation speeds, kinds of bioreactor and cellulase loadings, and comparison of the deactivation of three industrial cellulases at different states-free, absorbed by lignin and during filter paper hydrolysis was carried out. The results provided suggestions for the option of cellulases and cellulose hydrolysis conditions.