【作者】 张威；

【导师】 彭良才； 郝勃；

【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】 能源危机和全球气候变暖,导致人们迫切需要低成本的可再生能源。目前,木质纤维素被认为可以用来生产生物燃料。但由于生物质降解的屏障,生物质转化一直处于发展阶段。尽管人们为提高转化效率投入了大量精力,但预处理和酶解仍然是问题的关键所在。这主要是由于纤维素结晶度和木质素的交联结构所导致。因此阐明细胞壁结构以及细胞壁如何影响生物质降解转化效率,对当前发展生物质能具有重要意义。本研究筛选到6份芒草种质资源和3份玉米脆杆突变体,分别进行了0.25%(v/v)硫酸酸和0.5%(w/w)氢氧化钠预处理及酶解产糖测定。结果显示氢氧化钠处理后的酶解效率普遍高于硫酸。不同芒草材料的酶解效率差异较大,变化范围在8%-18%。细胞壁成分分析结果显示不同生物质秸秆的纤维素含量发生了显著变化,最高达50%,主要表现在晶体纤维素含量的改变。半纤维素含量和纤维素有相同变化趋势,主要表现在木糖和阿拉伯糖含量的变化,而木质素和果胶变化不明显。论文通过聚合度DP,分子数量和结晶度等3个指标来表征的结构,纤维素DP是晶体状纤维素DP的5-10倍,提取出的晶体纤维素摩尔数量却是总纤维素的5-10倍,说明纤维素微纤丝结构由多个结晶区和非结晶区组成。结果显示晶体纤维素的聚合度和结晶度与酶解效率呈负相关,晶体纤维素的分子数量与酶解效率成正相关。可以推测,纤维素聚合度和分子数量可能决定了细胞壁的组成和性质。更多还原

【Abstract】 Energy crisis and globe warming have led to an intensive demand for renewable and sustainable fuels. Currently, lignocelluloses biomass is considered for conversion to liquid fuels. However, biomass conversion is still under developing because of its recalcitrance. Despite that a great effort has been made to increase the lignocelluloses conversion rate, the difficulty remains with two crucial factors:biomass pretreatment and enzymatic degradation. It is determined by properties of the cellulose crystallinity and lignin intercross linking. Therefore, understanding of plant cell wall structure and its effects on biomass conversion is scientifically important for developing biofuels in the near future.In terms of the experiments, I initially collected several typical energy crops including 6 miscanthus germplasm and 3 brittle culm mutants of maize. Analyzed their enzymatic degradation after 0.25%(v/v)H2SO4 and 0.5%(w/w)NaOH pretreatments.The results indicated that enzymatic sugar release from H2SO4 treated miscanthus was higher than NaOH treated. And there were significant differences among these materials, from 8% to 18%.The cellulose structural features were characterized as DP value, molecule number and crystallinity. The DP of crude cellulose was 5-10 time more than the crystal cellulose, and the molecule number of crystal cellulose was 5-10 time more than the crude cellulose. It means the cellulose is constructed by a series of crystal sections and amorphous sections. The results also showed that the sugar yields released by enzymatic hydrolysis were closely correlated with the cellulose content, DP value and mole number of cellulose. A significantly negative correlation was tested between cellulose crystallinity and its degradation efficiency. Thus, it was concluded that the DP and mole number of cellulose can determine the composition and property of plant cell walls to some degree.更多还原