Fe-Mn-Mg离子对稻草秸秆酶解糖化的影响

发布时间：2018-05-18 00:31

  本文选题：稻草秸秆 + 酶解糖化　； 参考：《重庆大学》2015年硕士论文

【摘要】：农作物秸秆来源丰富,价格低廉,富含纤维素和半纤维素,是生产燃料酒精的重要原料。燃料酒精的制备主要包括预处理、糖化、发酵和分离提纯四个阶段。其中,糖化工艺既是检验预处理效果又是为发酵工艺提供原料的关键步骤。因此研究的焦点之一就是如何高产量低成本的获得还原糖。本论文以稻草秸秆为原料,液化预处理后,在糖化过程中添加微量金属离子,从优化工艺参数出发,以产糖量为表征,考察金属离子的单独作用和联合作用对酶解糖化过程的影响,并探究金属离子的作用机理。液化预处理结果表明,预处理后的稻草秸秆纤维素含量提高了20.9%,半纤维素和木质素含量分别降低了12.3%和5.35%,电镜扫描结果发现稻草秸秆预处理后结构松散,比表面积和孔隙度都大大增加,有利于纤维素酶和液化底物充分接触反应,提高酶解效果。在糖化过程中分别添加Mn2+和Fe2+离子,通过单因素实验优化研究金属离子添加量、酶用量、温度和时间对酶解糖化的影响。结果表明,在相同时间条件下,产糖量Fe2+离子组Mn2+离子组空白组。添加Mn2+离子时酶用量从空白组的25mg/g下降为20mg/g,添加Fe2+离子酶用量和空白组一致。适宜的酶解温度由50℃(空白)下降为40℃(Mn2+离子)和35℃(Fe2+离子)。在糖化过程中添加Mn2+和Fe2+离子能破坏纤维素的晶型结构,增加纤维素酶和液化底物的接触面积,同时还能提高酶活性,从而提高酶解效率,减少能耗。通过单因素实验和正交优化实验考察了Mg2+和Fe3+离子的单独作用对酶解糖化过程的影响。结果表明,空白组的较优工艺条件为酶用量25mg/g,温度50℃,糖化时间60h,产糖量343mg/g;Mg2+离子组的较优工艺条件为Mg2+离子添加量2mg/g,酶用量20mg/g,温度50℃,时间96h,产糖量高达477mg/g;Fe3+离子组的较优工艺条件为Fe3+离子添加量4mg/g,酶用量25mg/g,温度40℃,时间108h,产糖量达到400mg/g。在较优组合条件下,添加Mg2+和Fe3+离子产糖量相较于空白组分别提高了134mg/g和57mg/g。这与单因素实验所得结论在相同条件下产糖量Mg2+离子组Fe3+离子组空白组一致。探讨了Mg2+和Fe3+离子联合作用对稻草秸秆酶解糖化的影响。通过正交实验得到的较优工艺是在糖化过程中添加30mg/g纤维素酶和1:2的Mg2+、Fe3+离子,在40℃的温度条件下酶解84h,得到346mg/g还原糖。单因素结果表明Mg2+和Fe3+离子的联合作用比各自单独作用更有助于酶解效率的提高。
[Abstract]:Crop stalks are rich in cellulose and hemicellulose and are important raw materials for the production of fuel alcohol. The preparation of fuel alcohol mainly includes four stages: pretreatment, saccharification, fermentation and separation and purification. Saccharification process is not only the test of pretreatment effect, but also the key step to provide raw material for fermentation process. Therefore, one of the focuses of research is how to obtain reducing sugar with high production and low cost. In this paper, straw was used as raw material. After liquefaction pretreatment, trace metal ions were added in the saccharification process. The effects of metal ions on the process of enzymatic hydrolysis and saccharification were investigated, and the mechanism of metal ions action was investigated. The results of liquefaction pretreatment showed that the cellulose content of straw was increased by 20.9%, the content of hemicellulose and lignin decreased by 12.3% and 5.35%, respectively. The results of SEM showed that the structure of straw was loose after pretreatment. The increase of specific surface area and porosity is beneficial to the full contact reaction between cellulase and liquefaction substrate and to the improvement of enzymatic hydrolysis. Mn2 and Fe2 ions were added in the saccharification process, and the effects of metal ion addition amount, enzyme dosage, temperature and time on enzymatic hydrolysis and saccharification were optimized by single factor experiment. The results showed that under the same time, the sugar production Fe2 ion group Mn2 ion group blank group. The amount of enzyme was decreased from 20 mg / g to 20 mg / g in the blank group when the Mn2 ion was added, and the amount of the enzyme was the same as that in the blank group. The optimum enzymatic hydrolysis temperature was reduced from 50 鈩，

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