Synergistic Effect Of Mechanical Activation-Metal Salt On Pretreatment Of Sugarcane Bagsse And Its Enzymatic Saccharification

With the increased global environmental pollution and rapid exhaustion of natural resources,it is urgent to develop green,economic and renewable energy sources to replace the traditional fossil fuels.Lignocellulose is the most widely distributed and abundant renewable resource in nature,which has broad prospects for the development of fuel ethanol.However,the compact network structure of lignocellulose and the high crystalline structure of cellulose make it difficult for the cellulose to be contacted by the enzyme.So it is important to improve the accessibility and enzymatic hydrolysis of lignocellulose.On the basis of previous research of our group,synergistic interaction of mechanical activation(MA)-metal salt(MS)was applied to pretreat lignocellulose in this paper.Using sugarcane bagasse(SCB)as lignocellulosic materials and MSs as additives to study the solid synergistic effect of mechanical activation-metal salt on SCB,and investigate the influence of MS species and dosage on enzymatic saccharification of SCB.The results showed that the MS with better effect and better dosage were aluminum chloride,aluminum nitrate,ferric chloride,and ferric nitrate at 2,2.5,2.5,and 3.5 wt.%,respectively.Fixed MA temperature 50?,MA speed 500 rpm,MA time 60 min,enzyme activity dosage of 12 FPU·g-1 substrate,and with the best dosage of MS,the enzymatic saccharification rate of SCB pretreated by MA was 34.7%,but the enzymatic saccharification rate of SCB pretreated by MA-aluminum chloride,aluminum nitrate,ferric chloride,or ferric nitrate were 79.68,65.18,65.33,or 68.96%,respectively.SEM analysis showed that the surface structure of SCB was obviously changed by the pretreatment of MA and MA-MS.XRD analysis showed that the crystallinity of SCB decreased after MA and MA-MS pretreatment.The crystallinity of MA pretreated SCB decreased from 53.11%to 20.77%,but that of MA-aluminum chloride pretreated SCB decreased to 10.19%.FITR analysis showed that there was no chemical reaction occurred during the pretreatment.With the optimized metal salts as additives,the effects of MA temperature,MA speed,MA time and the amount of enzyme activity on the enzymatic hydrolysis of SCB were investigated.In addition,the structural characterization such as SEM,XRD,and FTIR were carried out to further analyze MA temperature,speed,and time on the stracture changes of SCB.The experimental results showed that the increase of MA speed,time and enzyme dosage had obvious effect on promoting the saccharification rate of SCB,but MA temperature had little effect.SEM analysis showed that with the increase of MA speed and time,the surface structure of SCB was damaged more serious.At low speed and short MA time,SCB was destroyed from smooth strips flake to block,and structure in higher speed and longer time it became granular.XRD analysis showed that the MA speed and time had significant effect on damaging the crystallization structure of SCB.Comparative analysis on the enzymatic hydrolysis rate of SCB and holecellulose.The results showed that lignin has a certain effect on the enzymatic hydrolysis of SCB.The analysis of residual enzyme activity of SCB,holecellulose and lignin showed that the pore structure of SCB and holecellulose could be destroyed by MA and MA-MS pretreatment,and then reduced the ineffective adsorption of enzyme.The structure properties analysis of lignin showed that hydroxyl content of lignin was increased and oxygen content was reduced by MA and MA-MS.In conclusion,the mechanism of MA and MA-MS pretreatment on lignocellulose was not only the destruction of its dense network structure and the stable crystalline structure,but the change of molecular structure of lignin to increase its content of hydrophilic group.Therefore the enzyme affinity of substrate was increased,and then increased the enzymatic saccharification rate of the lignocellulose substrate.