Urease-induced metallization of gold nanorods for the sensitive detection of Salmonella enterica Choleraesuis through colorimetric ELISA

We applied urease-induced silver metallization on the surface of gold nanorods (AuNR) to improve colorimetric ELISA for the rapid and sensitive detection of Salmonella enterica Choleraesuis. To this end, we introduced a biotin-streptavidin system as a bridge to determine the correlation between urease and S. enterica Choleraesuis concentrations. The captured urease can catalyze the hydrolysis of urea into carbon dioxide and ammonia, and the generated ammonia can then induce the deposition of silver shell on the surface of AuNR in the presence of silver nitrate and glucose. With the decreased aspect ratio (length divided by width) of AuNR, a multicolor change of AuNR solution and a significant blue shift in the longitudinal localized surface plasmon resonance absorption peak (Δλ_max) of AuNR were obtained at the target concentrations of 1.21 × 10¹ to 1.21 × 10⁸ cfu/mL. Consequently, the detection limits of our proposed colorimetric ELISA were as low as 1.21 × 10² cfu/mL for qualitative detection with naked eyes, and 1.21 × 10¹ cfu/mL for quantitative detection, in which changes in Δλ_max of AuNR were recorded with a microplate reader. These values were at least 2 to 3 orders of magnitude lower than those obtained with conventional horseradish peroxidase-based ELISA. The analytical performance of our developed colorimetric ELISA in terms of selectivity, accuracy, reliability, and practicability were investigated by analyzing S. enterica Choleraesuis-spiked pasteurized whole milk samples.     

薛荔籽果胶对去势雌性大鼠矿物质吸收的影响

目的:探讨薛荔籽果胶对去势雌性大鼠矿物质吸收的影响。方法:将30只SD成年雌鼠随机分为5组。4组大鼠做双侧卵巢切除手术,一周后分为空白组和薛荔籽果胶高、中、低剂量组;用伪切除同龄大鼠作对照(Sham组)。喂养4周后解剖,测定盲肠内容物pH值、短链脂肪酸、骨钙、骨磷含量及矿物质元素的表观吸收等指标。结果:去势雌性大鼠对钙、镁、磷、锌和铁元素的表观吸收率及骨钙和骨磷含量显著低于正常大鼠(P<0.05)。薛荔籽果胶能显著增加去势雌性大鼠短链脂肪酸含量和盲肠面积(P<0.05),降低盲肠pH值,并且在一定程度上抑制钙、镁、磷、锌和铁元素的表观吸收率。结论:薛荔籽果胶能降低去势雌性大鼠矿物质的表观吸收率。     

样品预处理对测定葡萄酒中二氧化硫残留结果的影响

通过样品预处理.对现行国标GB/T5009.34-2003盐酸副玫瑰苯胺法测定葡萄酒中游离二氧化硫残留方法进行改进.样品先加氢氧化钠溶液释放亚硫酸盐,再加盐酸游离二氧化硫.该方法回收率82.5～87.5%,国标和改进后的方法测定结果经统计学处理精密度分别为0.027±0.008和0.033±0.004(P＜0.01).     

Antioxidant and antibacterial activities of exopolysaccharides from Bifidobacterium bifidum WBIN03 and Lactobacillus plantarum R315

The objective of this study was to investigate the antioxidant and antibacterial activities of exopolysaccharide (EPS) from Bifidobacterium bifidum WBIN03 (B-EPS) and Lactobacillus plantarum R315 (L-EPS). The 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging, hydroxyl radical-scavenging, and superoxide radical-scavenging abilities were measured to evaluate antioxidant activity. Inhibition of erythrocyte hemolysis and lipid peroxidation was also measured. Both B-EPS and L-EPS had strong scavenging ability against DPPH and superoxide radicals at high concentration. The inhibitory effect of B-EPS on erythrocyte hemolysis was stronger than that of L-EPS in a concentration range from 0.30 to 1.00 mg/mL, whereas the hydroxyl scavenging ability of L-EPS (39.15 ± 0.58%) was significantly higher than that of 0.15 mg/mL ascorbic acid (24.33 ± 1.17%) and B-EPS (17.89 ± 3.30%) at 0.10 mg/mL. The inhibition of lipid peroxidation of 0.50 mg/mL B-EPS and L-EPS was 13.48 ± 1.74% and 12.43 ± 0.51%, respectively, values lower than that of ascorbic acid at the same concentration (23.20 ± 1.41%). Furthermore, all these abilities were enhanced in a concentration-dependent manner. Agar diffusion assay showed that both EPS exhibited antibacterial activities against tested pathogens such as Cronobacter sakazakii, Escherichia coli, Listeria monocytogenes, Staphyloccocus aureus, Candida albicans, Bacillus cereus, Salmonella typhimurium, and Shigella sonnei at 300 μg/mL. In conclusion, both EPS have antimicrobial and antioxidant activities and could have applications in the food industry.     

PTT纤维条的染色与水洗工艺研究

研究了染色与水洗技术对聚对苯二甲酸丙二醇酯纤维条低聚物残留量的影响。根据精梳毛纺针织纱生产实际,在分析聚对苯二甲酸丙二醇酯纤维中低聚物的残留对混条复精梳等纺纱工艺影响的基础上,针对聚对苯二甲酸丙二醇酯纤维及低聚物的特点,综合分析酸性及碱性染色的差异,解决了染料选择的关键问题。采用新型碱性染色工艺及水洗的方法,控制了低聚物的沉积。实验结果表明,新型碱性染色工艺技术能有效消除低聚物,提高聚对苯二甲酸丙二醇酯纤维条的染色质量,实现了新型纱线的正常生产。     

糖基表面活性剂研究进展

糖基表面活性剂原料来自天然可再生资源,具有良好的生物可降解性,广泛应用于日用品行业和食品工业中.本文概述了几种新型糖基表面活性剂的研究进展,并对糖基表面活性剂应用前景进行了展望.     

褐藻胶裂解酶产生菌的筛选、鉴定及其产酶条件研究

从土壤中分离得到的一株芽孢杆菌W1在以褐藻酸钠为唯一碳源的培养基中进行驯化后,在琼脂平板上产生透明水解圈,通过筛选得到实验菌株S1,鉴定后确定其为枯草芽孢杆菌.经过发酵培养实验,确定其最佳产酶条件:以蛋白胨和尿素为氮源,褐藻酸钠0.5～0.6%(质量分数),培养初始pH值7.5,培养温度32℃,180r/min摇床发酵84hr-108hr.     

西红柿的贮藏特性研究

以成熟的西红柿为材料,研究不同包装方式和贮藏温度下西红柿品质变化规律,为西红柿贮藏品质的控制提供依据.结果表明,温度和贮藏时间对西红柿的腐烂率、失重率、VC含量﹑总酸含量影响显著,包装方式只对外观和失重率影响显著.随着贮藏时间的延长和贮藏温度的升高,西红柿的腐烂和失重的速度和程度增加,VC含量﹑酸度随着贮藏温度的升高逐渐下降.膜包装比无膜包装的贮藏效果好.西红柿适宜的贮藏条件为采用膜包装于12℃下贮藏.在此条件下贮藏20天后,西红柿品质保持较好.     

Inhibition of the activity of mushroom tyrosinase by alkylbenzoic acids

The inhibition kinetics of alkylbenzoic acids on the diphenolase activity of mushroom tyrosinase have been investigated. The results show that the alkylbenzoic acids assayed can lead to reversible inhibition of the enzyme; furthermore, o-toluic acid and m-toluic acid are mixed-type inhibitors and p-alkylbenzoic acids are uncompetitive inhibitors. The inhibition constants have been determined. For these p-alkylbenzoic acids, the inhibition strength follows the order: p-toluic acid < p-ethylbenzoic acid < p-propylbenzoic acid < p-isopropylbenzoic acid < p-tert-butylbenzoic acid < p-butylbenzoic acid < p-pentylbenzoic acid < p-hexylbenzoic acid < p-heptylbenzoic acid < p-octylbenzoic acid, indicating that the hydrophobic p-alkyl group played an important role in the inhibition of the enzyme. The inhibitory effects were potentiated with increasing lengths of the hydrocarbon chains. The inhibitory effects of o-toluic acid and p-isopropylbenzoic acid on the monophenolase activity have also been studied. The results show that both o-toluic acid and p-isopropylbenzoic acid can lengthen the lag time and decrease the steady-state activity of the enzyme.     

柚皮果胶理化性质的研究

以柚皮干粉为原料提取果胶,采用正交实验优化柚皮果胶提取工艺,并对其理化性质进行检测。研究表明在提取温度100℃,pH2.0,时间60min,料液比1∶50(g/mL)的条件下柚皮果胶的得率最高,为27.06%,纯度达84.3%,酯化度为73.75%,所得果胶为淡黄色。常温下pH为4.86,属于酸性高酯果胶。柚皮果胶的溶解度随温度升高而增大、随着pH增大,溶解度有下降的趋势;柚皮果胶的热稳定性优于商品果胶,但随着时间增加迅速降低,15min后趋于稳定;柚皮果胶粘度与果胶浓度和蔗糖浓度的正相关,随pH的增大和温度的升高而下降;柚皮果胶理化性质与商品柑橘果胶相似,柚皮果胶的粘度和乳化性能优于商品柑橘果胶。实验结果表明柚皮果胶是一种优质的果胶。