纳米级银颗粒的制备方法

在简要介绍纳米银在各个工业领域应用的基础上,总结比较了各种制备纳米银颗粒的方法。物理和化学方法的工艺技术都比较成熟,但也存在着一定的不足。新兴的生物还原法因其具有微生物原料来源广,生物还原反应条件温和,产物纳米颗粒不易团聚,以及过程加入的化学试剂和产生的有毒副产物少等特点而开始受到关注。微生物还原金属离子有2种不同的机理：微生物的酶催化机理和非酶还原机理。对生物还原法原理的充分认识是将该方法发展成为可实际应用的纳米银制备工艺的重要基础。     

铁还原菌Shewanella xiamenensis BC01的有机溶剂应激研究

以铁还原菌厦门希瓦氏菌Shewanella xiamenensis BC01（SXM）为研究对象,系统探究了SXM在不同有机溶剂胁迫下的行为变化。生长方面,SXM对有机溶剂的耐受性与其亲水性相关,甲醇、乙醇、丙酮及DMSO的耐受浓度可达5%,对异丙醇、丙醇及叔丁醇的耐受浓度为2%,对丁醇的耐受浓度仅为1%。形态方面,丙醇刺激下的SXM菌体被显著拉长为至少5 μm以上,而丁醇刺激下菌体则缩小至平均不足1 μm,且均为可逆变化;蛋白方面,在丙醇与丁醇刺激下,与铁代谢相关的TonB、IucA及含铁脱氢酶等蛋白表达量均下调,铁还原酶活性也被大幅抑制;基因层面,丙醇刺激下与电子传递相关的mtrC基因表达量提高147.6%。     

模拟移动床色谱分离吴茱萸碱和吴茱萸次碱

以C18为固定相、甲醇/水=70/30（体积比）为流动相,利用三区带模拟移动床分离了两种生物碱,吴茱萸碱和吴茱萸次碱。通过前沿分析法测定了两种生物碱的吸附等温线,在实验浓度范围内符合线性吸附等温线,吴茱萸碱和吴茱萸次碱的亨利系数分别为3.11和5.25。利用经验公式估算了轴向扩散系数和有效传质系数。分别利用三角形理论和基于模型的优化方法对三区带模拟移动床的操作条件进行设计,在优化的条件下,最大进料流量为0.55 ml?min^-1,两种产品纯度均大于99%。通过异步切换策略,在不增加设备投资及保证产品纯度大于99%的前提下,将进料流量提高至0.62 ml?min^-1。     

运用试验读者设计方法提高胞外杂合β-葡聚糖酶在重组大肠杆菌中的表达

A genetically engineered Escherichia coli JM109 harboring pLF3 was used to produce a hybrid extracellular β-glucanase. Starting with enzyme production medium, glycerol and yeast extract combined with NaNO3 were screened to be the most suitable carbon and nitrogen source, respectively. Analysis of six components of the enzyme production medium by employing statistical optimization methods such as Plackett-Burman design and steepest ascent showed that yeast extract was the only significant variable and its best concentration for enzyme production was 12g·L-1. After optimization of the medium, 297.71U·ml-1 of β-glucanase activity in the medium and 352350U·g-1 of β-glucanase selectivity could be obtained, which were 14 and 72 folds higher than those obtained from original medium, respectively. Even higher enzyme activities were achieved by batch cultivations in a conventional stirred bioreactor on the optimized medium.