732阳离子交换树脂吸附L-组氨酸的特性

测定25℃下732阳离子交换树脂吸附L-组氨酸的动力学曲线和吸附等温线,考察了pH值、硫酸铵浓度、L-赖氨酸和L-精氨酸对吸附的影响。结果表明,Freund lich方程可以较好地描述732阳离子交换树脂对L-组氨酸的吸附,由Freund lich方程求得其平衡吸附量为142.32 g/L;吸附率随pH值的增大而减小,适宜在小于5.4时吸附;NH4+的存在使L-组氨酸的吸附率明显下降,当NH4+浓度达到1.0 mol/L时吸附率仅为42.32%;L-赖氨酸或L-精氨酸的存在使吸附率略微减小。     

L-组氨酸产生菌的诱变选育

通过选育得到1株L-组氨酸高产菌株,以液体发酵法培养谷氨酸棒杆菌、黄色短杆菌、粘质赛氏杆菌和枯草芽孢杆菌,用比色法测定其组氨酸产量。结果表明,黄色短杆菌产组氨酸最高,在添加150g/L葡萄糖,35g/L硫酸铵和10g/L蛋白胨的发酵培养基中培养72h,产L-组氨酸达128．28mg/L。     

常压室温等离子体诱变与微生物液滴培养系统联用筛选L-组氨酸产生菌

利用常压室温等离子体（ARTP）诱变技术,对野生型谷氨酸棒杆菌（Corynebacterium glutamicum）ATCC 14067诱变处理。通过全自动高通量微生物液滴培养系统（MMC）和平板选育组氨酸结构类似物的抗性突变株。使用48孔板发酵初筛及摇瓶发酵复筛,最终从耐受3-氨基-1,2,4-三氮唑10 g/L和D-组氨酸8 g/L的抗性突变株中筛选得到菌株Cg-F4,其L-组氨酸产量为（0.561±0.016）g/L,并且经过7次连续传代实验验证了该菌株稳定性良好。     

紫外线与氯化锂复合诱变选育L-组氨酸产生菌

以一株谷氨酸棒杆菌(Corynebacterium glutamicum)S6为出发菌株,利用氯化锂、紫外线进行诱变,通过实验证明氯化锂诱变剂量在1.2%时致死率达到82.4%,紫外线在照射30 s时致死率达到81.8%.利用氯化锂诱变谷氨酸棒杆菌S6,所得菌株D3的L-组氨酸产量为243 mg/L,比出发菌株提高10.5%;以紫外线做诱变S6,所得高产菌株U1产量256 mg/L,比出发菌株提高8.5%;以紫外线、氯化锂复合诱变S6,所得菌株N1产量为251 mg/L,比出发菌株提高13.6%,结果显示,经紫外线与氯化锂复合诱变后的菌株N1产L-组氨酸的产量最高,比氯化锂诱变后的菌株产L-组氨酸量提高3.1%,比紫外线诱变后的菌株产L-组氨酸量提高5.1%.     

Selective Transport of Cu2+ Ions through Bulk Liquid Membrane System Mediated by Erythromycin Ethyl Succinate

The carrier mediated transport of Cu²⁺ ions from an aqueous medium has been examined. The ability of Erythromycin Ethyl Succinate (EES) as a carrier to form a complex with Cu²⁺ ions and transport them to the receiving phase is reported. The fundamental parameters influencing the transport of Cu²⁺ ions such as the pH in the source and receiving phases and concentration of the stripping agent in the receiving phase have been optimized and accordingly, the amount of Cu²⁺ transported across the liquid membrane after 5 h was 94.3 ± 1.8% in the presence of L-histidine as a suitable stripping agent. Moreover, the selectivity and efficiency of Cu²⁺ ions transport from aqueous solution over other cations in ternary and quaternary mixtures have been investigated. The results indicate that our fabricated membrane is very sensitive toward Cu⁺² ions in the presence of heavy metal ions.     

阳离子交换树脂法制备L-组氨酸钙工艺

采用阳离子交换树脂法制备L-组氨酸螯合钙,测定了D151和110两种弱酸型阳离子交换树脂的钙离子交换容量及其在26℃下的交换动力学曲线,并考察了温度、NaOH与L-组氨酸摩尔比、L-组氨酸初始浓度和树脂量对2种树脂钙交换过程的影响. 结果表明,D151和110的钙交换容量分别为1.12和2.59 mmol/g;交换过程迅速,工业上交换0.5 h即可达到平衡;钙离子交换是一个放热过程,工业生产中可在室温下或低温下进行;适宜的NaOH与L-组氨酸摩尔比为(1~1.25):1;用D151树脂时适宜的L-组氨酸初始浓度和树脂量分别约为0.46 mol/L和0.125 g/mL;用110树脂时分别约为0.4 mol/L和0.15 g/mL.     

Optical and morphological studies of L-histidine functionalised silver nanoparticles synthesised by two different methods

Silver nanoparticles (NPs) functionalised with L-histidine is synthesised by a chemical reduction approach using two different methods of stirring – using a magnetic stirrer and an ultrasonicator. The former method exhibits a strong narrow absorption peak at 396 nm and the latter a blue-shifted weak broad plasmon band for the bare silver NPs. When the capping agent is incorporated, a single broad peak at low intensity evolves for the first method of stirring whereas two distinct peaks are noticed for the second. The Transmission Electron Microscope (TEM) results confirm the spherical shape of the silver NPs in the first case. In the second case, both spherical and elliptical particles are obtained. Zeta potential measurements further confirm the stability of the histidine-capped silver NPs in comparison with the pure silver NPs. A study of the variation of the plasmon peak with pH indicates that a basic medium favours the growth of the histidine-capped silver NPs. A surface-enhanced Raman scattering investigation confirms the adsorption of the capping molecule through the nitrogen of the imidazole ring with the carboxylate group pointing outwards. L-histidine-capped silver NPs can find application in biosensors and biomedicine, particularly when prepared by the magnetic stirrer method due to its greater stability.     

响应曲面法优化L-组氨酸锌螯合物的合成工艺

以L-组氨酸与硝酸锌为原料制备L-组氨酸锌螯合物,在单因素实验的基础上,运用响应曲面法对L-组氨酸锌螯合工艺条件进行优化,结果表明:最佳螯合条件:反应温度为50℃,pH为5,L-组氨酸∶Zn(NO3)2·6H2O为2∶1。在此条件下螯合率理论值为93.22%,验证实际螯合率为93.19%。通过比较螯合反应前后的红外光谱图证明了组氨酸锌螯合物的形成。     

组氨酸与氯化钾混合液对兔肉肌球蛋白特性的影响

目的：研究组氨酸与氯化钾混合液对肌球蛋白溶出率、聚集特性和热凝胶特性的影响。方法：提取纯化兔腰大肌肌球蛋白,并用含有组氨酸的盐溶液透析处理,测定不同离子强度条件下蛋白溶出率、浊度以及热诱导凝胶的硬度和保水性（water holding capacity,WHC）。结果：经组氨酸处理后,在低离子强度（1 mmol/L KCl）条件下肌球蛋白的溶出率从17.2%提高到64.4%,聚集程度显著下降,热凝胶的硬度和保水性显著提高（P＜0.05）;而在生理离子强度（0.15 mol/L KCl）和高离子强度（0.6 mol/L KCl）条件下肌球蛋白的溶出率和聚集特性均未受组氨酸处理的影响,但其热凝胶硬度值显著降低（P＜0.05）;虽然在高离子强度条件下肌球蛋白热凝胶的保水性显著降低（P＜0.05）,但是在生理离子强度条件下凝胶保水性没有发生变化。结论：组氨酸处理可以显著增强低离子强度条件下肌球蛋白溶出率和其热凝胶形成能力,是低钠凝胶类肉制品生产和研发的一个新思路。     

大肠杆菌L-组氨酸生物合成途径的改造及其对工程菌L-组氨酸产量的影响

改造大肠杆菌L-组氨酸生物合成途径,以提高L-组氨酸的产量．用NTG诱变大肠杆菌M-17（SG^r）,依次赋予其2噻唑丙氨酸（2-TA）和组氨酸氧肟酸盐（HisHx）遗传标记,再以突变株M-18（SG^r＋2-TA^r＋HisHx^r）基因组为模板,扩增组氨酸操纵子基因,构建出重组质粒pUC118-his—operon,将重组质粒导入突变株M—18（SG^r＋2-TA^r＋HisHx^r）得到工程菌Ecoli M-19（SG^r＋2．TA^r＋HisHx^r／pUC118-his—operon）．根据硝和prs基因序列分别合成引物进行PCR扩增,PCR产物与载体pSTV28连接,构建重组质粒pSTV28-zwf、pSTV28-prs和pSTV28-zwf-prs,将重组质粒分别转化至工程菌E．coli MZH-19,摇瓶发酵测定重组工程菌L-组氨酸的产量．摇瓶发酵结果显示,L-组氨酸产量与对照株相比,工程菌E．coli M-19提高了4．5倍,双质粒系统重组工程菌E．coli MZH-19、Ecoli MPH-19和E．coil MZPH-19分别提高了5．14、5．78、8．43倍．