Sodium Hydroxide-methanol Solution(SMs) Pretreatment Of Corn Stover And Enzymatic Hydrolysis For Producing Hydrolysates With High Concentrations Of Sugars

Lignocellulose,as the most abundant biomass energy in the world,has always played an important role in the research community.In recent years,researchers have developed a highly mature technology in converting crops to biofuel,but this process is obviously not economical and practical in the long run.Therefore,researchers try to use crop straw as raw material to prepare biofuels and have achieved staged success.Currently,the cost of biofuels produced from straw crops is high,owing to the tight structure of lignocellulose seriously hindering the degradation of cellulose.In this study,a new pretreatment of lignocellulose was described to improve the enzymatic hydrolysis performance of natural lignocellulose.According to the advantages of this process,fed-batch method has been used to enzyme hydrolysis at high solid-liquid ratio in order to produce high sugar concentration enzymatic hydrolysate.The experimental results were summarized as below:In this thesis,a sodium hydroxide-methanol solution(SMs)pretreatment of corn stover was described to overcome biomass recalcitrance.The effects of sodium hydroxide loading,solid-to-liquid ratio,processing time,processing temperature and moisture content on pretreatment were studied in detail,to determine the optimal pretreatment condition.97.5% glucan and 83.5% xylan were preserved in the regenerated corn stover under the optimal condition.Subsequently,enzymatic hydrolysis(5% w/v)was carried out,respectively.It was found that the SMs pretreatment could significantly enhance the enzyme accessibility of corn stover,and have the advantages of simple treatment,low energy consumption and low pollutant emission.Therefore,this technology has been considered commercially promising.In this thesis,a fed-batch enzymatic hydrolysis of the sodium hydroxide-methanol solution(SMs)pretreated corn stover was described to achieve high sugars concentrations.Effects of enzyme loading,initial solid loading,timing of feeding,feeding times and modes on enzymatic hydrolysis were studied in detail.Glucose,xylose,cello-oligosaccharides and xylo-oligosaccharides achieved 146.7 g/L,58.7 g/L,15.6 g/L and 24.7 g/L,respectively,when the fed-batch hydrolysis was initiated at 12% solid loading,and 7% fresh substrates and the corresponding enzyme(15 FPU/g substrate)were fed consecutively at 3,6,24 and 48 h to get a final solid loading of 40%.The monosaccharide conversion of glucan and xylan reached 86.5% and 61.0% respectively.It can be found that fed-batch hydrolysis can avoid many disadvantageous in batch hydrolysis,and significantly improve the enzyme hydrolysis speed and efficiency,resulting in high sugar concentration enzymatic hydrolysate.