Study On Pretreatment Process Of Ammonium Sulfite Of Bamboo And Its Enzymatic Hydrolysis Properties

The production of biofuel and bioproducts from renewable lignocellulosic material is one of the most popular renewable energy production methods.As an alternative to petrochemical refining,biological refining can make full use of existing lignocellulosic to produce energy and chemicals.It can not only reduce the dependence on fossil energy and the emission of greenhouse gases,but also is environmentally friendly and has attracted wide attention.The development of sugar platform compounds is one of the most important research area in the process of biorefinery.Based on the recalcitrance of lignocellulosic biomass,its enzymatic efficiency is quite low,so the pretreatment has become the dominate technology in the production of sugar platform compounds.Nowadays,the cost of pretreatment is one of the bottlenecks in restricting the biorefinery,therefore how to exploring high efficiency and low cost of pretreatment method is an important research direction.Based on the recent research of pretreatment on lignocellulosic materials around the world,this paper focuses on the effect of ammonium sulfite pretreatment for the enzymatic hydrolysis efficiency of moso bamboo.In order to find out the potential effect of ammonium sulfite pretreatment on bamboo for efficient enzymatic saccharification,various ammonium sulfite loadings(10%,20%,30% and 45%,based on dry bamboo)were conducted to pretreat bamboo at 180 °C for 1-8h with the solid–liquid ratio of 1:6,respectively.The chemical composition such as cellulose,hemicellulose,and lignin of the raw bamboo,pretreated substrates and spent liquors were analyzed.Besides,the enzymatic hydrolysis efficiency was also calculated to evaluate the effect of enzymatic hydrolysis of bamboo pretreated by ammonium sulfite.The result showed that this pretreatment has a significant effect on the chemical composition and enzymatic hydrolysis of bamboo,can remove lignin to the greatest extent while retaining the carbohydrate in bamboo,and significantly improve the enzymatic hydrolysis efficiency which could achieve almost 100% in some cases.Finally,XRD,SEM and other characterization methods were used to observe the substrate of bamboo after pretreatment.The results showed that the relative crystallinity of cellulose was increased and the surface of bamboo became rough after ammonium sulfite pretreatment,through this method the accessibility of enzyme absorb on cellulose was increased and improved the efficiency of the enzyme hydrolysis of pretreated bamboo.The chemical compositions of the pretreated spent liquors were also determined,which was including monosaccharide,acid-soluble lignin,and the amount of fermentation inhibitors such as formic acid,acetic acid,furfural and 5-hydroxymethyl furfural.In this paper,based on the initial result of ammonium sulfite pretreatment of bamboo,and meanwhile in order to optimize the reaction conditions,reduce the intensity of reaction and pretreatment cost,the optimal condition of ammonium sulfite pretreatment of bamboo was further explored through the response surface analysis based on the box-behnken design.Through a series of experiments and model fitting,the model of the influence of pretreatment time,ammonium sulfite concentration and pretreatment temperature on total cellulose recovery was established.The result showed that the total cellulose recovery yield after pretreatment and48 h enzymatic hydrolysis could reach 58.36%?59.87%.The optimized condition of pretreatment was 20% ammonium sulfite loading at 150 °C for 6h,and the glucose yield of practical experiment was in agreement with the predicted yield(58.87%).To summarize,the chemical composition and enzymatic hydrolysis of bamboo is signifificantly affected by the ammonium sulfite pretreatment.The present research was to preliminarily assess the effect of this pretreatment method and provide elementary data for its commercial utilization in the future.