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秸秆预处理水解液对酶解的影响及资源化利用研究
李云
学位类型博士
导师万印华
2016-07
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业生物化工
关键词水稻秸秆 木质素 酚酸 超滤 纳滤
摘要

利用廉价、丰富的木质纤维素进行生物炼制对社会的可持续发展具有非常重要的意义。本文对秸秆碱水解液中木质素和酚类对纤维素酶水解的影响、碱处理黑液循环利用、酚类物质的回收,以及稀酸水解液纳滤分离过程的污染控制等进行了详细研究。主要结果如下:(1)考察了不同分子量的碱木质素对纤维素酶水解效率的影响,发现碱木质素都能促进酶水解,并且是分子量越大的木质素促进作用越显著。而这些是与木质素对纤维素酶的吸附亲和性、木质素带电性和亲疏水性相关的。(2)详细研究了碱水解液中香草醛对纤维素酶水解的抑制特性。结果表明,香草醛是纤维素酶的非竞争性抑制剂;香草醛中酚羟基和醛基抑制纤维素酶水解,而甲氧基无抑制作用。(3)采用超滤法回收水解液中木质素,结果表明,高压和低流速会产生较高的膜污染。超滤透过液循环4次,对水稻秸秆进行预处理,能达到与新鲜碱液类似的脱木质素和酶水解效果。碱循环使预处理过程水和碱的消耗量分别降低了42%和50%。(4)采用纳滤对碱水解液超滤透过液的羟基肉桂酸进行分离纯化。结果表明在中性pH时能达到最好的分离性能。同时,pH和盐浓度对酚醛截留率的影响存在协同作用。最后,对实际料液进行纳滤实验,羟基肉桂酸的纯度达到91.4%。(5)采用不同方法对稀酸水解液进行前处理,再进行纳滤实验。结果表明,活性炭吸附能更有效的提高纳滤浓缩倍数和单糖的浓度,同时去除抑制剂;稀酸水解中的酚类物质和色素可能是引起纳滤膜污染的主要物质。

其他摘要

Bioconversion of cheap, renewable and abundant lignocellulosic biomass to produce biofuels or biochemicals is very meaningful in sustaining the development of our economy and society. In this dissertation, the effect of alkali lignin with different molecular weights on cellulase, the inhibition mechanism of inhibitors (phenolics) produced by pretreatment, alkali recycling, the separation and concentration of phenolics, and the membrane fouling mechanism during nanofiltration (NF) applied in dilute acid hydrolysate were systematically investigated. The main results can be sumaried as follows:(1) The effect of alkali lignins with different molecular weight on the enzymatic hydrolysis of lignocellulose was studied. The results showed that the addition of all the alkali lignins enhanced the hydrolysis of rice straw. The level of enhancement was related to the molecular weight of lignins. The level of enhancement was related to the molecular weight of lignins. Langmuir adsorption results showed that the alkali lignin with higher molecular weight had low affinity with cellulase. And the surface charge and hydrophobicity of alkali lignins also confirmed the results.(2) The effect of vanillin on cellulase activity for the hydrolysis of cellulose was investigated in detail. The results clearly showed that vanillin could reversibly and non-competitively inhibit the cellulase activity. Moreover, investigation of the effect of each group on phenyl ring of vanillin on cellulase activity demonstrated that aldehyde group and phenolic hydroxyl groups of vanillin had inhibitory effect on cellulase.(3) Lignin recovery from the alkaline rice straw hydrolyzate by ceramic ultrafiltration was investigated in terms of lignin retention and fouling mechanisms. The results showed that the relative higher cross-flow velocity and lower pressure led to less resistance and membrane fouling. The alkaline solution from ultrafiltration permeate was recycled for the pretreatment of fresh rice straw after simple pH adjustment. It was found that the reuse of alkali was feasible. The consumptions of NaOH and water were reduced by 42% and 50% respectively during pretreatments with reuse of alkali.(4) The separation and concentration of hydroxycinnamic acids from phenolic aldehydes were investigated using nanofiltration (NF) membrane with model solution and practical hydrolyzate. The results indicated that the separation performance of hydroxycinnamic acids from aldehydes was optimal at neutral pH. Salt and pH acted synergistic effect on phenolic aldehydes retention. When the practical alkaline hydrolyzate was treated under concentration-diafiltration mode, the purity of hydroxycinnamic acids was high up to 91.4%.(5) The influence of five pre-treatments i.e. on NF performance and membrane fouling were examined. The results showed that AC adsorption achieved the biggest volume reduction ratio (VRR) and decreased the membrane fouling. The results indicated that AC adsorption could be a useful pre-treatment before NF. In addition, phenolics and pigment might be the main components leading to severe fouling during NF process. 

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/22897
专题研究所(批量导入)
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李云. 秸秆预处理水解液对酶解的影响及资源化利用研究[D]. 北京. 中国科学院研究生院,2016.
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