【作者】 李晓；

【导师】 王曙光；

【作者基本信息】 山东大学 ， 环境工程（专业学位）， 2016， 硕士

【摘要】 硒是人体生理活动过程中非常重要的微量元素,体内缺硒以及摄入过量的硒均会导致相应的病症。世界上有很多地区缺硒,我国也属于非常缺乏硒元素的地区之一,研究和发展补硒类型的保健食物刻不容缓。硒纳米颗粒(SeNPs)属于纳米级的单质硒,其不仅具有补硒效应,还具有较高的生物活性以及较低的生物毒性,食用安全性得到比较有效的改良,因此在食品领域得到比较广泛的应用。本文选用解淀粉芽孢杆菌为实验菌种,利用其对高价态硒(亚硒酸钠)的还原作用,将SeO32-还原成单质Se0,制备胶体状硒纳米颗粒。本文探究了胞外聚合物(EPS)在合成硒纳米颗粒过程中所起的作用,EPS是含有蛋白质成分的复杂有机层,它在硒纳米颗粒的还原过程中起重要作用,且硒纳米颗粒被EPS包裹有助于它的长期稳定。本论文探讨了反应时间、温度、pH、菌液初始浓度、摇床转速、装液量等对硒纳米颗粒转化率的影响,并寻找最佳反应条件。然而当前生物法制备硒纳米颗粒转化率较低、稳定性较差,因此我们试图寻找一种方法来提高解淀粉芽孢杆菌EPS中蛋白质及其他官能团的性质,进而提高硒纳米颗粒的转化率。本研究中分别使用胎牛血清(FBS)和壳聚糖(chitosan)作为添加剂,用来促进细胞生长,提高生物酶活性,进而达到加快反应速度,提高硒纳米颗粒转化率,提高颗粒分散稳定性,优化制备的硒纳米颗粒性状的目的。本论文还探究了添加剂胎牛血清或者壳聚糖对解淀粉芽孢杆菌EPS组分及结构的影响。FT-IR光谱和XPS光谱证明添加胎牛血清或者壳聚糖后,EPS中蛋白质和碳水化合物及其它官能团都有一定程度的增加,部分官能团的结构也产生一定的变化,这将促进细胞活性,进而提高氧化还原反应的速度以及硒纳米颗粒的转化效率。XRD和EDX分析表明,胎牛血清或者壳聚糖的添加,使硒纳米颗粒不仅在数量上有一定程度的增加,还具有更高的结晶度,以及更稳定的性质,这表明胎牛血清或者壳聚糖的添加可以优化硒纳米颗粒的性状。此外,ζ-电位分析表明,添加了胎牛血清或者壳聚糖之后,生成的硒纳米颗粒具有更高的ζ-电位和等电点,使硒纳米颗粒具有更高的分散稳定性,有利于硒纳米颗粒的长期储存。更多还原

【Abstract】 Selenium (Se) is an essential element for human physiological activity. Neither selenium excess nor selenium deficiency would be beneficial to biological health. Most of the countrys and reagions in the world, especially china were in the lack of selenium supplyment from food. The development of the health food rich of selenium would gain a promising expectation because of the huge-but long-term market-demand of this kind of selenium food.Selenium nanoparticles (SeNPs) is one of the type of elemental selenium with nano-size. SeNPs possess the ability to supply selenium to human body with low toxicity. The bio-safety of selenium to humanbody would be improved to a certain extent by selenium nanoparticles. Thus the study on selenium nanoparticles becomes one of the most important prospects when developing selenium supplement with high efficiency but limited toxic effects.In this paper, the Bacillus amyloliquefaciens was elected to be the experimental strains to synthesize the biosynthetic selenium nanoparticles (BioSeNPs) with its reduction ability for the reduction of SeO32-to elemental selenium nanoparticles (SeNPs). Meantime, this study investigated the role of EPS in synthesizing BioSeNPs, BioSeNPs were covered by an organic layer contained proteins component, which were responsible and long term stabilization of BioSeNPs. In this paper, we investigate the effects of reaction time, temperature, pH, initial concentration of bacteria, rotation speed, liquid volume on selenium nanoparticles conversion rates in order to find the best experimental conditions. However, the conversion rate of SeNPs was relatively low by the current biological method. Therefore, we try to find a way to improve the properties of proteins and other component functional groups in extracellular polymeric substances (EPS) of Bacillus amyloliquefaciens in order to improve the conversion rate of SeNPs. In this paper, we use the fetal bovine serum (FBS) or chitosanas theadditional agent, which could promote cell growth, enhance the biological activity of the enzyme, and thus increase the reaction rate, improve the conversion rate of SeNPs, optimizing selenium nanoparticles traits and stabilize the SeNPs. This study investigated the effect of FBS and chitosan on component and structure of EPS. FT-IR spectroscopy and XPS measurements confirmed the increasing of proteins and carbohydrates by additional FBS and chitosan in Bacillus amyloliquefaciens, which would promote the cell activities, conversion efficiency and reaction rate of BioSeNPs. XRD and EDX analysis showed that this synthesis method yielded a large amount of stable colloidal spherical BioSeNPs with high crystallinity in the presence of FBS and chitosan. Furthermore, compared with BioSeNPs, FBS-BioSeNPs had a higher ζ-potential and iso-electric point that can improve the stability of BioSeNPs.更多还原