微波辅助DMSO/AmimCl复合溶剂预处理玉米秸秆的酶解影响

Saccharification of the Pretreated Corn Stover by Microwave Assisted DMSO/AmimCl Co-solvents

为了实现玉米秸秆纤维素的高效糖化,设计利用微波加热辅助的离子液体1-烯丙基-3-甲基咪唑氯盐(AmimCl)/二甲基亚砜(DMSO)复合溶剂生物质预处理体系,破坏玉米秸秆天然结构,提高纤维素酶解效率.研究发现,15%(w)DMSO,110℃,60 min及4 g秸秆/100 g复合溶剂为最适预处理条件.在此条件下,秸秆溶解率、提取率可分别达46.6%和22.9%;提取物纤维素酶解率14 h可达71.4%,相较于天然玉米秸秆的20 h酶解率12.5%有极大提高.通过XRD,SEM及1H NMR分析发现:秸秆预处理后,提取物纤维素晶型由I型变为II型,残渣纤维素相对结晶度明显降低,有利于纤维素酶解的进行,达到了生物质预处理的目的;预处理过程中使用的AmimCl离子液体经简单回收再生,结构及秸秆溶解性能未发生变化,可循环使用.为玉米秸秆生物质预处理提供了一个新的方案.

In order to enhance the enzymatic saccharification efficiency of corn stover,microwave assisted treatment with dimethyl sulfoxide（DMSO） and 1-ally-3-methylimidazolium（AmimCl） co-solvents was designed to break up the complicated chemical structure of corn stover.The pretreatment conditions were studied to increase the dissolution ratio,extraction ratio and cellulose I crystallinity index（CrI） variation.With the increase of AmimCl concentration,time and temperature of the pretreatment,the dissolution ratio,extraction ratio increased and CrI decreased.Considering the costs of high AmimCl concentration,degradation of biomass at high temperature and long time,the optimum conditions were DMSO/AmimCl co-solvents with a DMSO concentration of 15%（w） and 4 g corn stover per 100 g co-solvents.The optimum temperature and time were 110 ℃ and 60 min,respectively.Under the optimal conditions,the ratios of corn stover dissolution and extraction were as high as 46.6% and 22.9%,respectively.The cellulose saccharification ratio had a great increase within 14 h of enzymatic hydrolysis with an enzyme loading amount of 14 FPU/g solids.The saccharification ratio for the extracts was 71.4% in 14 h,while the ratio was only 12.5% for the raw corn stover in 20 h.Powder X-ray diffraction was used to determine the cellulose crystal structure.The cellulose I crystallinity index of corn stover residues decreased obviously and the crystal form of AmimCl extracts were transformed from I to II.From the SEM pictures of the materials,it could be seen that the outer surface of corn stover residues became rough,which was good for enzyme accessibility and saccharification.The AmimCl extracts had lost their natural status completely.By simple vacuum distillation,AmimCl could be recycled and its solubility kept almost constant.According to1H NMR spectroscopy analysis,the structures of fresh and recycled AmimCl were almost the same.From the results mentioned above,it can be concluded that microwave assisted treatment with DMSO AmimCl co-solvents was a feasible method for corn stover pretreatment.