【作者】 杨青丹；

【导师】 王克勤；

【作者基本信息】 湖南农业大学 ， 农产品加工及贮藏工程， 2011， 硕士

【摘要】 积极开发可再生能源是应对能源危机和环境污染的有效途径之一。生物质能源是全球储存量最丰富的可再生能源之一。生物质能源的生产原料主要是存量丰富的天然木质纤维素。如何有效破坏天然木质纤维素原料的结构以提高其酶解反应性能是目前生产生物乙醇的瓶颈。目前,物理、化学、生物、物理化学、组合方法等方法广泛应用于天然木质纤维素原料的预处理,但这些方法都存在如效率低、成本高、污染环境等缺点,故寻找新的方法是非常必要的。本研究建立和完善了稻草纤维素、半纤维素、木质素含量的分析方法,分析测定了60Coγ射线辐照处理的稻草纤维素、半纤维素、木质素含量；采用离子色谱定性、定量测定水溶性糖；采用扫描电镜观察稻草表观形态变化；采用FTIR仪对辐照的单糖、寡糖、纯纤维素及木质素结构分析；研究稻草辐照结合酶解进行糖化效果；优化了辐照酶解参数,建立了稻草辐照酶解的优化工艺；研究了分别经辐照预处理和蒸汽爆破预处理稻草中各种水溶性糖的含量和同一条件下酶解效果,为稻草产辐照预处理技术提供了理论依据和技术支撑。本文的主要研究结果如下：1稻草成分分析方法建立稻草纤维素、半纤维素、木质素含量测定方法。先测定中性洗涤纤维和酸性洗涤纤维含量,再用70%乙酸溶解木质素；根据差重计算出纤维素、半纤维素、木质素含量分别为35.88%、23.98%、11.19%。采用离子色谱测定稻草中水溶性糖。未经预处理的稻草中水溶性糖只有少量的乳果糖、葡萄糖和纤维二糖。2辐照预处理后稻草纤维素、半纤维素、木质素含量变化在0kGy-2000kGy剂量范围内,纤维素和半纤维素含量随辐照剂量升高而降低；纤维素含量从30.73%降低到21.93%,半纤维素从10.15%降低到5.28%；木质素含量从8.88%降低到7.25%。3辐照预处理后稻草表观形态变化采用扫描电镜观察辐照预处理后稻草表观形态的变化。稻草表面形态在低剂量辐照下没有变化；在800kGy剂量以上孔度变多,表面变得疏松、不平整,特别是在2000 kGy剂量辐照下变化剧烈,内表面孔隙变更大。4辐照处理后单糖、寡糖、纯纤维素及木质素结构特征分析采用红外光谱仪分析辐照处理后单糖、寡糖、纯纤维素及木质素结构特征分析。辐照预处理后,单糖、寡糖和纯纤维素中C-O-C结构氧化降解产生C=O功能团；木质素的苯环结构发生变化。5稻草酶解工艺优化研究采用L9(34)正交试验优化得到稻草酶解最佳条件：酶解温度为45℃,酶用量180 U.g-1,酶解时间60h,液固比为60：1。酶解温度、酶用量和酶解时间对稻草酶解产糖影响显著；液固比影响不显著。6稻草辐照酶解的工艺优化研究采用L9(34)正交试验优化得到稻草辐照酶解最佳条件：酶用量150 U.g-1,辐照剂量800kGy,酶解时间48h,液固比50：1。酶用量和辐照剂量对稻草酶解产糖影响显著；酶解时间和液固比影响不显著。7稻草辐照预处理与蒸汽爆破预处理对比通过研究预处理对稻草水溶性糖和酶解效果的影响,明确辐照预处理比蒸汽爆破预处理效果好。与辐照预处理相比,经蒸汽爆破预处理稻草的葡萄糖和木糖总量较小,水苏糖、棉子糖和葡萄糖醛酸产量较大；在相同酶解条件下,经800 kGy处理和2.0Mpa 2.0min蒸汽爆破预处理稻草葡萄糖和木糖总量分别达到90.355 mg.g-1和85.448mg.g-1。更多还原

【Abstract】 To actively develop renewable energy is an alternative way to cope with the energy crisis and environmental pollution.The biomass energy is one of the most abundant renewable energy source. The major raw material of biomass energy is natural lignocellulose. How to disrupt lignocellulose structure and to improve enzymatic hydrolysis is the bottleneck of biofuel product.At present, there are many methods have been widely used to pretreat natural lignocellulose materials, such as physical method, chemical method, biological method, physical & chemical method, combining method and so on. However,there are some drawbacks,such as low efficiency, high cost,pollut environment and so on.Therefore it is necessary to develop new pretreative technology.The analysis method was establish to determine the content of the cellulose, hemicellulose and lignin of 60Co y-rays irradiated rice straw. Soluble sugars were measured qualitatively and quantitatively by Ion chromatography.The apparent structures of irradiated rice straw were scanned by electronmicroscope.The structures of irradiated monosaccharide,oligosaccharide,pure cellulose and lignin were analysed by Infrared transform spectrometer.Treated by both irradiation and enzyme,rice straw’s saccharification effect was researched.Parameters of irradiation and enzymolysis of rice straw were studied and optimization technology were established.Water-soluble sugars and enzymolysis effect of rice straw were researched, which was pretreated by irradiation and steam explosion respectively.These researches provide theoretical and technical supports for irradiation pretreatment.The experimentsal results as follows:1 Analytical methods of rice straw’s compositionThe method to determine cellulose,hemicellulose and lignin content was established.NDF and ANF were measured at first,then using 70% acetic acid to dissolve lignin. According to sent heavy, the contents of cellulose, hemicellulose and lignin in rice straw were 23.98%,35.88%,11.19% respectively.Water-soluble sugars in rice straw were determined by IC. There were a little lactulose, glucose and cellobiose in rice straw without pretreatment.2 The variation of cellulose, hemicellulose and lignin content in irradiated rice strawThe variation of cellulose, hemicellulose and lignin content in irradiated rice straw was acquired definitely.From OkGy to 2000kGy, with irradiation dose rising, the content of cellulose was reduced from 30.73% to 21.93%; the content of hemicell uloserise was 10.15% to 5.28%; the contents of lignin was reduced from 8.88% to 7.25%.3 Analysis the apparent structures of irradiated rice strawThe apparent structures of irradiated rice straw was analysed by SEM.The apparent structures of irradiated rice straw had no change at low dose,but above 800kGy doses,it becomed porosity and loose. Internal surface becomed more porosity at 2000 kGy.4 Analysis the structural feature of irradiated monosaccharide, oligosaccharide, pure cellulose and ligninThe structural feature of irradiated monosaccharide, oligosaccharide, pure cellulose and lignin was analysed by Infrared spectrometer. The C-O-C structure in monosaccharide,oligosaccharide and pure cellulose was oxidatived to C=O structure. The cyclobenzene of lignin was influenced by irradiation treatment.5 Optimization of enzymolysis of rice strawOptimal enzymatic hydrolysis conditions of rice straw were 45℃enzymatic hydrolysis temperature,180U/g enzyme dosage,60h enzymatic hydrolysis time and 60:1 liquid-solid ratio. It was optimized by Lg(34) orthogonal experiment. The influence of enzymatic hydrolysis temperature, enzyme dosage, enzymatic hydrolysis time was significant. The influence of liquid-solid ratio was not significant.6 Optimization of enzymolysis of irradiated rice strawOptimal enzymatic conditions of irradiated rice straw were 150 U/g enzyme dosage, 800kGy irradiational dose,48h enzymatic hydrolysis time and 50:1 liquid-solid ratio. It was optimized by L9(3) orthogonal experiment. The influence of enzyme dosage and irradiational dose was significant. The influence of enzymatic hydrolysis time and liquid-solid ratio was not significant.7 Contrast y-irradiation and steam explosion pretreatment to rice strawContrast y-irradiation and steam explosion pretreatment to rice straw.Compared to irradiative pretreatment, the content of glucose and xylose in steam explosive rice straw was smaller.But the contents of stachyose, gossypose and glucuronic acid were larger. At the same enzymatic conditions, the contents of glucose and xylose were 90.355 mg/g and 85.448 mg/g respectively,which from 800kGy dose and 2.0 Mpa 2.0 min steam explosion pretreatment rice straw respectively.更多还原