能源植物细胞壁成分与稀酸处理降解转化关系的研究
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摘要
随着人们对全球气候变暖和能源危机的关注,发展非石油燃料成为社会的普遍认识。纤维乙醇能够减少温室气体的排放并且不会产生“与人争粮”的问题,因此受到广泛的关注。
木质纤维素是植物体的主要构成物质,由纤维素、半纤维素、木质素、果胶质等生物高分子所组成。它是生产纤维乙醇的主要原料,而且它自身成分结构特点严重阻碍了生物质的降解转化。本课题通过稀硫酸处理植物秸秆来研究细胞壁成分对生物质降解转化的影响。
芒草材料间的纤维素和半纤维素含量差异较大,木质素含量变化相对较小。水稻的材料间纤维素含量差异较小,但是半纤维素、木质素含量差异较大。芒草的三大细胞壁成分含量都比水稻高。在稀酸预处理中,随着H2SO4浓度的提高,芒草和水稻的总糖产率也在提高。芒草的预处理五碳糖产率比水稻高,而水稻的预处理六碳糖产率比芒草高。芒草和水稻材料间的降解差异性不会随着酸浓度的改变而改变。晶体状纤维素、木质素不利于酶解产糖,而半纤维素、酸溶性木质素和糖醛酸有利于酶解产糖。酸碱组合处理结果表明,酶解产糖率高的材料在预处理中相应的五碳糖产率高,即半纤维素易于降解,而酶解产糖率低的材料则相反。
电镜观察表明,稀酸处理后秸秆表面比较光洁而且纤维素原纤保存完整。水稻和芒草的精细分析结果表明,酶解产糖率高的材料的纤维素结晶度较低、半纤维素组成单糖中木糖含量较高。在酸和碱处理中材料间的降解差异趋势一致,即酸处理中产糖率高的材料在碱处理中的产糖率也高。
Concerns about global climate and energy supply lead to seeking a non-petroleum-based fuels. Use of cellulosic-ethanol offers several benefits towards reduction of the greenhouse gas emissions and preventing of the competition with food supplies.
Ligno-cellulosic biomass is a natural complex primarily consisting of three biopolymers:cellulose, hemicelluloses and lignin. Biomass recalcitrance is the largest obstacle to emerging cellulosic ethanol biorefineries. The purpose of this study was to identify Miscanthus and rice cell wall composition that influence the effectiveness with a dilute acid pretreatment process.
The results showed that cellulose and hemicelluloses contents were varied among Miscanthus tested samples, with a little change in lignin. Compared to Miscanthus, rice is greatly varied in the hemicellulose and lignin contents. With increasing H2SO4 concentrations, total sugar yields were raised in both Miscanthus and rice. Particularly, pentose released from Miscanthus is more than one in rice, and hexose in rice is more than in Miscanthus's. Pretreatment by different acid concentrations, the difference of degradation in the Miscanthus and rice were not much changed. Crystalline cellulose and lignin have a negative effect on the enzymatic hydrolysis. The hemicelluloses, acid soluble lignin and uronic acid contents have a positive effect on the enzymatic hydrolysis. The degradation of the combined acid and alkali treatments showed that hemicelluloses are the crucial factors for biomass degradation in Miscanthus. The results of scanning electronic microscopy showed that major microfibrous cellulose structures remain after acid treatment.
Materials which have high rate of enzymatic hydrolysis also have a lower degree of crystallinity, and more xylose. The difference of degradation in the Miscanthus and rice by acid was consistent with pretreatment of alkali.
木质纤维素是植物体的主要构成物质,由纤维素、半纤维素、木质素、果胶质等生物高分子所组成。它是生产纤维乙醇的主要原料,而且它自身成分结构特点严重阻碍了生物质的降解转化。本课题通过稀硫酸处理植物秸秆来研究细胞壁成分对生物质降解转化的影响。
芒草材料间的纤维素和半纤维素含量差异较大,木质素含量变化相对较小。水稻的材料间纤维素含量差异较小,但是半纤维素、木质素含量差异较大。芒草的三大细胞壁成分含量都比水稻高。在稀酸预处理中,随着H2SO4浓度的提高,芒草和水稻的总糖产率也在提高。芒草的预处理五碳糖产率比水稻高,而水稻的预处理六碳糖产率比芒草高。芒草和水稻材料间的降解差异性不会随着酸浓度的改变而改变。晶体状纤维素、木质素不利于酶解产糖,而半纤维素、酸溶性木质素和糖醛酸有利于酶解产糖。酸碱组合处理结果表明,酶解产糖率高的材料在预处理中相应的五碳糖产率高,即半纤维素易于降解,而酶解产糖率低的材料则相反。
电镜观察表明,稀酸处理后秸秆表面比较光洁而且纤维素原纤保存完整。水稻和芒草的精细分析结果表明,酶解产糖率高的材料的纤维素结晶度较低、半纤维素组成单糖中木糖含量较高。在酸和碱处理中材料间的降解差异趋势一致,即酸处理中产糖率高的材料在碱处理中的产糖率也高。
Concerns about global climate and energy supply lead to seeking a non-petroleum-based fuels. Use of cellulosic-ethanol offers several benefits towards reduction of the greenhouse gas emissions and preventing of the competition with food supplies.
Ligno-cellulosic biomass is a natural complex primarily consisting of three biopolymers:cellulose, hemicelluloses and lignin. Biomass recalcitrance is the largest obstacle to emerging cellulosic ethanol biorefineries. The purpose of this study was to identify Miscanthus and rice cell wall composition that influence the effectiveness with a dilute acid pretreatment process.
The results showed that cellulose and hemicelluloses contents were varied among Miscanthus tested samples, with a little change in lignin. Compared to Miscanthus, rice is greatly varied in the hemicellulose and lignin contents. With increasing H2SO4 concentrations, total sugar yields were raised in both Miscanthus and rice. Particularly, pentose released from Miscanthus is more than one in rice, and hexose in rice is more than in Miscanthus's. Pretreatment by different acid concentrations, the difference of degradation in the Miscanthus and rice were not much changed. Crystalline cellulose and lignin have a negative effect on the enzymatic hydrolysis. The hemicelluloses, acid soluble lignin and uronic acid contents have a positive effect on the enzymatic hydrolysis. The degradation of the combined acid and alkali treatments showed that hemicelluloses are the crucial factors for biomass degradation in Miscanthus. The results of scanning electronic microscopy showed that major microfibrous cellulose structures remain after acid treatment.
Materials which have high rate of enzymatic hydrolysis also have a lower degree of crystallinity, and more xylose. The difference of degradation in the Miscanthus and rice by acid was consistent with pretreatment of alkali.
引文
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2.蒋应梯,许炯.竹纤维素分子聚合度的粘度测定法及其应用.林产化工通讯,2005,39：24-27
3.李高扬,李建龙,王艳等.优良能源植物筛选及评价指标探讨.可再生能源,2007,25：84-89
4.李军,吴平治,李美茹等.能源植物的研究进展及其发展趋势.自然杂志,2007,29：21-25
5.林仁权,胡文兰,陈国亮.重铬酸钾氧化分光光度法测定酒中乙醇含量.浙江预防医学,2006,18：78-79
6.彭良才.论中国生物能源发展的根本出路.华中农业大学学报(社科),2011,(2)：1-6
7.石元春.非粮生物质新能源最适合中国国情.山西能源与节能,2010,1-3
8.田春龙,郭斌,刘春朝.能源植物研究现状和展望.生物加工过程,2005,3：14-19
9.田宜水.中国第二代生物燃料资源发展潜力分析.中国能源,2010,32：17-20
10.王伟波,张全发.能源植物规模化种植理论与技术研究进展.生命科学,2010,22：1271-1276
11.王亚静,毕于运,唐华俊.中国能源作物制备液体生物燃料现状及发展趋势.可再生能源,2009,27：100-105
12.吴国江,刘杰,娄治平等.能源植物的研究现状及发展建议.中国科学院院刊,2006,21：53-57
13.谢光辉,卓岳,赵亚丽等.欧美根茎能源植物研究现状及其在我国北方的资源潜力.中国农业大学学报,2008,13：11-18
14. Alvira, P., Tomas-Pejo, E., Ballesteros, M., et al. Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis:A review. Bioresource Technol,2010,101:4851-4861
15. Anderson, W., and Akin, D. Structural and chemical properties of grass lignocelluloses related to conversion for biofuels. J. Ind. Microbiol. Biotechnol,2008, 35:355-366
16. Arioli, T., Peng, L., Betzner, A.S., et al. Molecular Analysis of Cellulose Biosynthesis in Arabidopsis. Science,1998,279:717-720
17. Atalla, R.H., Hackney, J.M., Uhlin, I., et al. Hemicelluloses as structure regulators in the aggregation of native cellulose. Int J Biol Macromol,1993,15:109-112
18. Balat, M., Balat, H., and Oz, C. Progress in bioethanol processing. Prog. Energy Combust. Sci,2008,34:551-573
19. Billa, E., Tollier, M.-T., and Monties, B. Characterisation of the Monomeric Composition of in situ Wheat Straw Lignins by Alkaline Nitrobenzene Oxidation: Effect of Temperature and Reaction Time. J Sci Food Agr,1996,72:250-256
20. Binod, P., Sindhu, R., Singhania, R.R., et al. Bioethanol production from rice straw: An overview. Bioresource Technol,2010,101:4767-4774
21. Buranov, A.U., and Mazza, G. Lignin in straw of herbaceous crops. Ind Crop Prod, 2008,28:237-259
22. Chen, F., and Dixon, R.A. Lignin modification improves fermentable sugar yields for biofuel production. Nat Biotech,2007,25:759-761
23. Davin, L.B., and Lewis, N.G. Lignin primary structures and dirigent sites. Curr Opin in Biotechnol,2005,16:407-415
24. De la Luz Reus Medina, M., and Kumar, V. Comparative evaluation of powder and tableting properties of low and high degree of polymerization cellulose I and cellulose II excipients. Int. J. Pharm,2007,337:202-209
25. Ebringerova, A., Hromadkova, Z., and Heinze, T. Hemicellulose. Adv Polym Sci, 2005,186:1-67
26. Gray, K.A., Zhao, L., and Emptage, M. Bioethanol. Curr Opin Chem Biol,2006,10: 141-146
27. Hahn-Hagerdal, B., Galbe, M., Gorwa-Grauslund, M.F., et al. Bio-ethanol-the fuel of tomorrow from the residues of today. Trends Biotechnol,2006,24:549-556
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