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微波辅助二甲基亚砜/AmimCl复合溶剂预处理生物质及对其糖化效果影响的研究
刘建飞
Subtype硕士
Thesis Advisor邢建民 ; 李会泉
2013-05-01
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline生物化工
Keyword1-ally-3-methylimidazolium Chloride   木质纤维素生物质   预处理   糖化   酶活
Abstract生物质中含有的木质素、半纤维素及部分结晶态的纤维素,造成生物质酶可及度低等问题。因此,生物质利用前须经预处理,以破坏其天然结构。利用绿色室温离子液体破除生物质的紧凑结构,可以达到较理想的生物质预处理效果。论文研究了1-allyl-3-methylimidazolium chloride(AmimCl)对纤维素酶活性的影响及其对三类生物质预处理性能的不同。对比分析了农业废弃物和木屑在AmimCl中的溶解性能情况,比较了不同生物质的溶解率、提取率、XRD曲线,NMR曲线、SEM图像及成分和酶解率的变化等。 (1)生物质经预处理将有离子液体残留,残留的离子液体可能影响酶蛋白的活性。通过研究AmimCl对纤维素酶活性的影响,发现AmimCl对纤维素酶活性的影响是可逆的且在AmimCl溶液中,当粗纤维素酶(cellulase,140 FPU/g)浓度不高于0.2(w/v)%,蛋白质浓度≤0.017(w/v)%时,AmimCl浓度对纤维素酶活性无影响。 (2)考察了AmimCl预处理生物质及其对生物质酶解情况的影响。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)%二甲基亚砜,4 g秸秆/100 g复合溶剂,110 oC处理60 min为最佳预处理条件。在此条件下,秸秆溶解率和提取率可分别达到46.6%和22.9%;提取物纤维素含量较天然玉米秸秆提高了12%;提取物14 h纤维素酶解率可达71.4%,相较于天然玉米秸秆(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,可循环使用。因此,AmimCl/二甲基亚砜复合溶剂系统为玉米秸秆生物质预处理提供了一个新的方法。 (3)为了进一步提高AmimCl预处理生物质的性能,对比了硬木(楸木、杨木和梧桐木)、软木(松木)和农业秸秆废弃物(麦秸、稻草和玉米秸秆)三类物质在微波加热辅助的二甲基亚砜/AmimCl复合溶剂中的溶解性能。不同生物质在复合溶剂中的溶解性能顺序为:汽爆玉米秸秆>软木>农业秸秆废弃物>硬木。松木溶解率及提取率可分别达到54.3%和31.7%。经预处理后,松木提取物的纤维素晶型发生改变,由I型变为II型,纤维素含量提高到85.1%,相应的酶解率提高到85.4%。玉米秸秆经汽爆预处理后能够完全溶解于DMSO/AmimCl复合溶剂中,且溶解后再生产物14 h酶解糖化率可达到91.5%。生物质纤维素I相对结晶度及聚合度越低,越有利于离子液体AmimCl的预处理。
Other AbstractThe presence of lignin in plant cell wall, together with the partially crystalline structure of cellulose fibrils, results in a compact structure and low accessibilities to enzymes. So, pretreatment is urgently needed for biomass utilization. A promising approach is using the “green” ionic liquids (ILs) to break the compact structure of lignocellulose firstly. In this thesis, the effects of 1-allyl-3-methylimidazolium chloride (AmimCl) on the activity of cellulase and its dissolution influences on three kinds of biomasses were anlyzed. The dissolution ratio, extraction ratio, XRD curve, NMR curve, SEM images, concentration variation and enzymatic hydrolysis ratio of different conditions were studied. (1) The residual ILs might affect the following enzymatic hydrolysis process. After investigating the effects of AmimCl on the activities of cellulase, it was concluded that the influence of AmimCl on cellulase activity was reversible. For the crude celluase (140 FPU/g), AmimCl had no effect on it when its concentration was less than 0.2 (w/v) %, the concentration of the soluble protein was less than 0.017%. When the enzyme activity was higher than 4117.5 FPU/(g soluble protein), there was no need to wash off all the residual AmimCl (≤5%) in order to get the best saccharification ratio. (2) Microwave heating assisted AmimCl/dimethyl sulfoxide (DMSO) co-solvents was used to investigate the pretreatment effect on corn stover. 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 oC 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 content for CS extracts was increased by 12%. 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 (CrI) 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, the outer surface of corn stover residues became rough, which was good for enzyme accessibility and saccharification. The AmimCl extracts lost their natural status completely. By simple vacuum distillation, AmimCl could be recycled and its solubility kept almost constant. According to 1H 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. (3) A simple and efficient way, microwave assisted DMSO/AmimCl pretreatment, was proposed to enhance biomass saccharification. Softwood (pine wood/PW), hardwoods (poplar wood, catalpa bungi and Chinese parasol) and agricultural wastes (rice straw, wheat straw and corn stover/CS) were exploited. Results showed that the best pretreatment effect could be observed in PW with dissolution and extraction ratios at 54.30% and 31.68%, severally. The crystal form of cellulose in PW extract was transferred from I to II, and its cellulose and glucose conversion ratios reached 83.13% and 60.51%, respectively. CS after steam explosion got a similar pretreating effect as PW. The glucose conversion ratio could reach to 91.5%. It is speculated that natural biomasses with lower cellulose I crystallinity index and degree of polymerization, better AmimCl solubility could be got.
Pages85
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8273
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
刘建飞. 微波辅助二甲基亚砜/AmimCl复合溶剂预处理生物质及对其糖化效果影响的研究[D]. 北京. 中国科学院研究生院,2013.
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