【作者】 徐宁；

【导师】 彭良才； 李庆；

【作者基本信息】 华中农业大学 ， 生物化学与分子生物学， 2011， 硕士

【摘要】 能源危机和温室效应日益加剧,生物能源作为一种清洁的可再生能源,成为化石燃料的理想替代能源。木质纤维素作为植物细胞壁的主要成分,是地球上最丰富的生物质资源,木质纤维素转化生物乙醇具有广阔的利用前景,所以,细胞壁成分和结构的研究具有重要的意义。本研究选取芒草(C4植物)和水稻(C3植物)为材料,通过NaOH预处理,分析细胞壁成分的变化对预处理和酶解产糖效率的影响。测定纤维素、半纤维素、木质素、果胶质,四者总和为细胞壁总成分。五节芒细胞壁中的木质素(25.42%-32.14%)显著变化,纤维素和半纤维素没有显著变化；南荻细胞壁中的半纤维素(25.40%-30.00%)显著变化,木质素(31.36%-33.91%)小幅度变化,纤维素没有显著变化,水稻细胞壁中的半纤维素(27.97-19.66%)显著变化,纤维素和木质素没有显著变化。随NaOH浓度的提高,五节芒预处理液六碳糖、五碳糖、酶解液六碳糖含量大幅增加,而酶解液五碳糖的含量在1.00%NaOH达到最高值；随NaOH浓度的提高,南荻预处理液中五碳糖大幅增加,而预处理液中六碳糖小幅增加,酶解液中六碳糖和五碳糖增长明显；随NaOH浓度的提高,水稻预处理液中六碳糖含量在0.50%-1.00%NaOH增长幅度很大,预处理液中的五碳糖呈梯度升高,酶解液中的六碳糖稳定增加,酶解液中五碳糖在1.00% NaOH达到最高。通过分析胞壁结构和碱处理降解转化效率可以发现,五节芒的产糖率主要受木质素影响,木质素越高,产糖率越低；南荻随木质素升高产糖率降低,但半纤维素升高会显著提升产糖效率,半纤维素和木质素同样影响南荻产糖效率,水稻产糖效率主要受半纤维素影响,半纤维素升高,产糖效率升高。通过测定实验材料的精细成分发现,木质素S单体覆盖在纤维素表面,是降低酶解效率的主要屏障；而南荻XM4的非晶体纤维素为7.30%,显著提高了酶解效率,说明非晶体纤维素会促进纤维素的水解,提高酶解效率。更多还原

【Abstract】 Concerns about energy crisis and globe warming have been seriously raised over the world. Biomass utilization is increasingly considered as a practical way for sustainable energy supply and long-term environment care around the world. Lignocellulose is the most abundant renewable biomass on the earth and is the major component of the plant cell walls. Understanding of cell wall molecular structure is important for Biomass pretreatment and Bioethanol production. In this study, Miscanthus (C4) and Rice (C3) were used:o analyze their cell wall composition and digestibility upon NaOH pretreatment and subsequent enzyme degradation.The plant cell walls are composed of cellulose, hemicelluloses, lignins and pectins. The results showed that total lignin contents were most varied among the tested samples of miscanthus. M.floridulus samples were not much altered in the contents of the hemicelluloses and cellulose, whereas M.lutarioriparius showed a little change in hemicelluloses. As a comaprison, rice samples are greatly changed only in the hemicellulose contents.With the increased concentrations of NaOH, most samples (Hexose of pretreatment, Pentose of pretreatment & Hexose of enzymolysis) in Miscanthus appeared to have a significantly elvated degestibility of biomass. One sample (Pentose of enzymolysis) can reach to the highest activity at 1% NaOH among the M.floridulus, and two samples (Hexose of enzymolysis and Pentose of enzymolysis) showed much higher biomass degradation than others in M.lutarioriparius. Only three rice samples (Pentose of pretreatment, Pentose of pretreatment & Pentose of enzymolysis) showed high degradation efficiency.In addition, we analysed the relationship between the plant cell wall composition and the efficiency of biomass pretreatment and enzymolysis. It is characterized that lignins are the major factors for biomass degradation in M.floridulus, and hemicelluloses and lignins both played an important role in M.lutarioriparius. As a difference, hemicelluloses are the crucial factors for biomass degradation in rice.In Miscanthus, the S monomer of lignins is the key factor inhibiting enzyme degradation, and the non-crystalline cellulose could result in an increased efficiency of the biomass digestion.更多还原