小麦秸秆原料生物炼制制备乳链菌肽的研究

发布时间：2018-06-08 03:21

  本文选题：乳链菌肽 + 小麦秸秆　； 参考：《陕西科技大学》2017年硕士论文

【摘要】：乳链菌肽(Nisin)是由乳酸链球菌或乳酸乳球菌发酵产生的一类阳离子疏水性的小分子多肽化合物,属于微生物抗菌肽,具有无毒、不产生抗药性等特点,被认为是安全绿色的食品防腐剂。近年来乳链菌肽被认为是非常具潜力的抗生素替代品,在医药行业中有广泛的应用前景。秸秆作为无限可再生的生物质资源,来源广泛、价格低廉,但对其不恰当的处理会造成严重的环境污染。利用秸秆原料生物炼制乳链菌肽,为乳链菌肽的生产提供了一种新的原料,使秸秆资源得到有效利用,增加秸秆原料生物炼制的产品。本文以小麦秸秆为原料,研究秸秆的预处理、酶解、秸秆水解液培养基组成以及分批发酵过程控制等环节的技术参数,主要研究内容和实验结果如下:(1)研究影响预处理的各因素,采用正交实验对碱预处理小麦秸秆的条件进行优化,并对其进行表征。研究结果表明,碱浓度和时间对预处理效果影响十分显著,且小麦秸秆预处理最佳条件为:反应温度50℃,料液比1:40,碱浓度3.5%,反应时间30 h。在此条件下,还原糖得率为34.35%。通过对预处理前后的小麦秸秆进行扫描电镜、X衍射以及红外光谱分析,得出碱预处理小麦秸秆可以脱除秸秆中的绝大部分木质素和少部分的半纤维素,并使纤维素发生润胀,使致密的小麦秸秆表面出现一些裂缝和裂痕,从而使得纤维素酶与纤维素的接触面积增加,促进酶解反应的进行。(2)研究影响复合酶酶解效果的各因素,使用Box-Behnken实验来优化酶解条件,构建响应面模型。通过响应面分析得出最优酶解条件为:复合酶的添加量32.5 mg/g,反应时间23.87 h,pH值4.57,温度50.9℃,料液比1:28.6,在此条件下,还原糖得率为51.22%,水解液中还原糖含量为37 g/L。成功构建响应面模型,且响应面模型的准确率达91.24%。(3)对小麦秸秆水解液培养基的氮源、磷源以及营养物质的种类和含量进行研究,采用正交实验对其进行优化。结果表明玉米浆的添加量对发酵生产乳链菌肽有着显著的影响,适于嗜热乳链球菌6032发酵生产乳链菌肽的水解液培养基组成为:酵母膏13 g/L,磷酸氢二钾4.5 g/L,乙酸钠5 g/L,柠檬酸氢二铵2 g/L,硫酸镁0.58 g/L,硫酸锰0.24 g/L,玉米浆32%,还原糖含量37 g/L的小麦秸秆水解液。发酵所得乳链菌肽效价为5752 IU/mL。(4)研究影响发酵条件的各因素,采用Box-Behnken实验来优化发酵条件,建立响应面模型。对响应面进行分析得出发酵过程中发酵液的pH值对发酵生产乳链菌肽有着十分显著的影响,转速对发酵生产乳链菌肽的影响次之,温度和初始pH值对发酵的影响较小,并得出最优发酵条件为:发酵初始pH值7,发酵过程中发酵液pH值维持在5.6,发酵温度30℃,转速为49 r/min,在此条件下,Nisin效价可达到6172 IU/mL。并对构建的响应面模型进行实验验证,模型的重现率达96.36%。
[Abstract]:Nisin is a kind of small cationic hydrophobic polypeptide produced by the fermentation of Streptococcus lactis or Lactococcus lactis. Food preservatives considered safe and green. In recent years, nisin has been considered as a potential substitute for antibiotics, and has a wide application prospect in the pharmaceutical industry. Straw, as an unlimited renewable biomass resource, has a wide range of sources and low price, but improper treatment will cause serious environmental pollution. A new raw material for the production of nisin is provided by biological refining of the raw material of straw, which can make the straw resource be effectively utilized and increase the product of biological refining of the raw material of straw. In this paper, wheat straw was used as raw material to study the technical parameters of straw pretreatment, enzymatic hydrolysis, composition of straw hydrolysate medium and control of batch fermentation process. The main contents and experimental results are as follows: (1) the factors affecting pretreatment were studied. The conditions of alkali pretreatment of wheat straw were optimized and characterized by orthogonal experiment. The results showed that the effect of alkali concentration and time on the pretreatment was very significant, and the optimum conditions of wheat straw pretreatment were as follows: reaction temperature 50 鈩，

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