"One-Pot" Preparation Of Cellulosic Ethanol By The Short-Time Hydrothermal Depolymerization Pretreatment-Enzymatic Hydrolysis-Fermentation From Sugarcane Bagasse

The promotion of the resource utilization of biomass is one of the effective approaches to achieve“carbon peaking and carbon neutrality”,which meets the needs of the development of environmental protection,energy saving and low-carbon economy in China.Cellulosic ethanol produced from agricultural and forestry wastes is a low-carbon,non-food-competitive fuel.In view of the problems of cumbersome pretreatment process,high water and energy consumption,large wastewater and waste discharge,and low utilization of cellulose and hemicellulose currently existing in the preparation process of cellulosic ethanol.Therefore,it is urgent to develop a green,environmentally friendly and sustainable bioethanol production process on an industrial scale.Liquid hot water（LHW）pretreatment uses water as the only reagent,without adding any chemical reagent or catalyst,which is environmentally friendly,low cost,and has good solubility for hemicellulose.In the thesis,firstly,using sugarcane bagasse（SCB）as raw material,the LHW pretreatment was combined with“one-pot method”to investigate the effects of pretreatment conditions on the production of cellulosic ethanol by whole slurry.After LHW pretreatment,the pretreated material was kept in the whole slurry and the enzymatic hydrolysis and fermentation process were optimized.The results showed that the pretreatment was carried out under the optimal pretreatment conditions at solid to liquid ratio（SLR）of 1:20（w/v）and the temperature at 210℃for a short retention time（0 min）.Furthermore,after p H adjustment,the pretreated SCB was hydrolyzed and fermented separately in one pot.This process achieved a high sugar conversion of 84.52±1.24%,containing 88.61±1.57%of glucose and 78.01±1.63%of xylose.Moreover,the concentration of ethanol obtained was 11.36±0.21 g/L and ethanol yield reached 257±6 mg/g _SCB,which was77.56±1.64%of the theoretical ethanol conversion from SCB.However,pre-hydrolysis for 24h and the simultaneous saccharification and fermentation processes could shorten preparation time and improve the productivity of ethanol preparation,which achieving an ethanol mass yield of 237±4 mg/g _SCB（71.63±1.27%of the theoretical ethanol yield）.Secondly,the mass and economic balance of the ethanol preparation process was carried out,and the preparation method of LHW pretreatment combined with“one-pot”was applied to other raw materials（corn cob,wheat straw,rice straw）.The results confirmed that cellulose and hemicellulose were retained in the solid and liquid components and there was no wastewater and waste discharge because most of the pretreatment steps were omitted.Furthermore,the use rate of fermentable sugar was improved,the preparation cost was reduced and the energy consumption was saved,reflecting the advantage of whole slurry retention,and that is an economical and feasible ethanol preparation method.Besides,this method could also be applied to other raw materials to obtain low-toxic hydrolyzate,and realize the preparation of ethanol by whole slurry,which has high applicability and application potential to raw materialsFinally,to realize the fermentation of the enzymatic hydrolysate at high SLR of 1:6（w/v）,we used a hyper-cross-linked polymeric adsorbent of SY-01 to detoxify the enzymatic hydrolysate after the investigation of inhibitor factors and resin screening.The results showed that detoxification by static or dynamic adsorption,SY-01 resin could achieve nearly 100%removal of furfural,5-hydroxymethylfurfural（5-HMF）,pigment and acid soluble lignin（ASL）in enzymatic hydrolysate.Moreover,SY-01 resin had a better removal of acetic acid,with the highest removal rate of 35.41%under static adsorption and 38.27%under dynamic adsorption.After detoxification by SY-01 fixed-bed column of 5-bed volume（BV）enzymatic hydrolysate,89.27±1.07%of fermentable sugars were recovered,and the total sugar concentration was68.31±0.39 g/L.Besides,the detoxification broth was fermented successfully and the highest ethanol concentration was 30.94±0.13 g/L.Furthermore,the ethanol yield of fermentation was102.51±0.94%and the ethanol yield from SCB was 210±1 mg/g _SCB,which achieved63.41±0.26%of the theoretical ethanol conversion from SCB.It is confirmed that SY-01 has high adsorption performance for the inhibitor of lignocellulose enzymatic hydrolysate,which provides an economical and feasible way for the detoxification of lignocellulose high-solid system and its application in ethanol production.