Effect of ultraviolet-C light on quality and microbial population of fresh-cut watermelon

The influence of ultraviolet (UV-C) light (1.4–13.7 kJ m⁻² at 254 nm) on the quality and microbial populations of fresh-cut watermelon [Citrulus lanatus (Thunb.) Matsum. and Nakai] was investigated and compared to that of common sanitizing solutions used for fresh-cut produce. Dipping cubes in chlorine (40 μL L⁻¹) and ozone (0.4 μL L⁻¹) was not effective in reducing microbial populations and quality was lower in cubes receiving these aqueous treatments compared to UV-irradiated cubes or control. In commercial trials, exposing packaged watermelons cubes to UV-C light at 4.1 kJ m⁻² produced >1 log reduction in microbial populations by the end of the product's shelf life without affecting juice leakage, color and, overall visual quality. In further experimentation, lower UV-C dose (1.4 kJ m⁻²) reduced microbial populations to a lower degree and only when complete surface exposure was ensured. Higher UV-C doses did not show any difference in microbial populations (6.3 kJ m⁻²) or result in quality deterioration (13.7 kJ m⁻²). Spray applications of hydrogen peroxide (2%) and chlorine (40 μL L⁻¹), without subsequent removal of excess water, failed to further decrease microbial load of cubes exposed to UV-C light at 4.1 kJ m⁻². When properly utilized, UV-C light is the only method tested in this study that could potentially be used for sanitizing fresh-cut watermelon.     

Comparison of serum lipid compositions, lipid peroxide, alpha-tocopherol and lipoproteins in captive marine mammals (bottlenose dolphins, spotted seals and West Indian manatees) and terrestrial mammals

Concentrations of serum lipid components, lipid peroxide (LPO) and α-tocopherol and electrophoretic patterns of lipoproteins in serum samples obtained from captive marine mammals and terrestrial mammals were compared. Serum concentrations of total cholesterol, free fatty acid, and phospholipid in fish-eating animals were significantly higher than those in manatees and cows. Serum LPO and α-tocopherol concentrations in the fish-eating animals were also significantly higher than those in manatees, cows and dogs. Different patterns of densitometric scans of low density lipoprotein (LDL) and a significantly lower percentage of LDL were demonstrated in the dolphins compared with the seals, cow and dogs. The concentration of LPO was significantly correlated with triglyceride and phospholipid concentrations in serum from the dolphins. These results suggest that triglyceride and phospholipid are susceptible to oxidative reaction in fish-eating animals. Evaluation of serum lipids, LPO and α-tocopherol concentrations is needed for nutritional husbandry for fish-eating animals.     

Assessment of microbial activity in water based on hydrogen peroxide decomposition rates

This study proposes a new and simple assay that allows rapid assessment of microbial activity in water samples. The assay consists of standardized hydrogen peroxide (H₂O₂) addition to a water sample and subsequent spectrophotometric determination of H₂O₂ reduction over time. The H₂O₂ decomposition rate constant reflects the level of enzymatic activity from planktonic and particle-associated bacteria as well as algae and protozoans. The proof of concept was verified on water samples from recirculating aquaculture systems (RAS), showing that the vast majority of H₂O₂ decomposition was related to microbial activity. Only 3% of the total H₂O₂ decomposition was related to abiotic processes when 0.20 μm sterile filtered RAS water was compared with unfiltered RAS water. Planktonic bacteria (size range 0.20–1.6 μm) accounted for 16% of H₂O₂ decomposition, while bacterial aggregates, particle-associated bacteria and microbiota above 1.6 μm were responsible for the remaining 81%. H₂O₂ decomposition rate constants were positively correlated to BOD₅ (r = 0.893; p < 0.001; n = 18) and to the number of 1–30 μm micro particles (r = 0.909; p < 0.001; n = 72) in RAS water, substantiating the biologically mediated decomposition processes in the water phase. The H₂O₂ decomposition assay thus represents a new alternative to existing methods that allows rapid (1–2 h) and simple quantification of microbial activity in fresh- and saltwater samples from aquaculture systems. Potential applications of the assay are discussed.     

不同处理方法对菊花中二氧化硫含量的影响

以菊花为研究对象,研究了热水浸泡、过氧化氢溶液浸泡及超声波处理的脱硫效果,结果显示,3种处理方式都可以有效地降低菊花中二氧化硫残留量,超声波处理效果最佳。正交试验优选出的脱硫方法是将菊花浸泡于30℃0.05%过氧化氢溶液中,超声处理6h。     

Expression of an oxalate oxidase gene in tomato and severity of disease caused by Botrytis cinerea and Sclerotinia sclerotiorum

A cDNA clone of wheat oxalate oxidase (OxO) under the control of the constitutive CAMV 35S promotor was expressed in tomato plants by Agrobacterium -mediated transformation. Twenty-six transgenic tomato lines were obtained and analysed. PCR experiments confirmed the incorporation of the OxO gene in all tested tomato lines. The transgenic tomato plants expressed a 124-kDa protein showing OxO activity, and were able to convert different oxalic acid (OA) concentrations in vitro . In a detached leaf assay, most of the transgenic lines showed reduced disease symptoms compared with controls, following inoculation with Botrytis cinerea . In addition, leaves of the line T15 showed a marked reduction in symptoms compared with the control following inoculation with Sclerotinia sclerotiorum .     

饲料中添加谷胱甘肽对凡纳滨对虾肝胰腺抗氧化指标和脂质过氧化物含量的影响

采用1种对照饲料和5种添加不同水平还原型谷胱甘肽（GSH）（添加量分别为60、120、180、240和300 mg·kg-1）的试验饲料,饲喂初始体重约为1.12 g的凡纳滨对虾（Litopenaeus vannamei）,分别命名为G0、G60、G120、G180、G240和G300组,经8周饲养后,观察饲料中不同浓度的GSH对凡纳滨对虾生长性能、肝胰腺抗氧化指标和脂质过氧化物含量的影响。结果表明,南美白对虾的增重率随着饲料中GSH添加量的增加而增加,在G180组达到高峰,但随着GSH添加量的进一步增加,增重率呈下降趋势（P<0.05）;饲料转化率随饲料中GSH添加量的升高而显著升高,在G240组达到最高（P<0.05）;成活率随饲料中GSH添加量的增加而显著提高,提高幅度为8.53%~31.69%。饲料中添加GSH能不同程度地提高凡纳滨对虾肝胰腺中抗氧化酶活力（P<0.05）,其中G60、G120组的谷胱甘肽还原酶,G120、G180和G300组的超氧化物歧化酶,G120、G180和G240组的谷胱甘肽过氧化物酶活力,分别显著高于对照组G0（P<0.05）。各试验组肝胰腺中GSH含量和总抗氧化能力比对照组G0分别提高了8.93%~52.57%和3.02%~37.03%,且呈剂量――效应关系。对虾肝胰腺中的活性氧含量随着日粮中GSH添加量的增加呈现下降的趋势,其中G180、G240组显著低于对照组（P<0.05）;与对照组相比,试验各组肝胰腺丙二醛含量显著降低（P<0.05）,抗O2-能力升高,在G120、G180、G240和G300组达到显著水平（P<0.05）。研究结果初步表明,饲料中添加一定量的GSH能提高凡纳滨对虾生长性能和肝胰腺抗氧化能力并降低脂质过氧化物含量。表4参18     

H2O2与葡萄VvIPK2基因表达及其低温胁迫响应的关系

 以葡萄砧木品种‘F-242’试管苗为材料,克隆了葡萄（Vitis L.）的多磷酸肌醇激酶（inositol polyphosphate kinase,IPK2）基因VvIPK2,并对其进行生物信息学分析;利用实时定量PCR和植物生理学技术,结合药理学实验探究了H2O2在葡萄响应低温胁迫中的作用及其与VvIPK2的关系。结果表明,克隆的VvIPK2其推导的翻译产物（VvIPK2）与数据库中推测的氨基酸序列一致;与栽培亚麻和拟南芥多磷酸肌醇激酶高度同源。在低温胁迫下,叶片VvIPK2表达与H2O2水平均明显升高;外源H2O2能提高VvIPK2表达水平,而H2O2清除剂抗坏血酸（ascorbic acid,AsA）降低VvIPK2表达水平。外施一定浓度的H2O2可提高超氧化物歧化酶（superoxide dismutase,SOD）活性,上调Cu/Zn SOD基因表达,降低丙二醛（malondialdehyde,MDA）含量和细胞膜相对透性;但IPK2抑制剂LY-294002对内源H2O2却无明显影响;LY-294002和AsA均能降低SOD活性,下调Cu/Zn SOD基因表达,提高MDA含量和细胞膜相对透性。推测H2O2调节VvIPK2的表达,参与葡萄响应低温胁迫过程。     

Effect of hydrogen peroxide and/or Flavobacterium psychrophilum on the gills of rainbow trout,Oncorhynchus mykiss (Walbaum)

The immune response and morphological changes in the gills of rainbow trout fry after immersion in hydrogen peroxide (H₂O₂), Flavobacterium psychrophilum or combined exposure were examined. The gills were sampled 4, 48, 125 and 192 h after exposure, and the regulation of expression of the following genes was investigated using qPCR: IgT, IgM, CD8, CD4, MHC I, MHC II, IL-4/13A, TcR-β, IL-10, IL-1β, IL-17, SAA and FoxP3. Bacteria were not observed in haematoxylin-and-eosin-stained gill tissue, but the presence of F. psychrophilum 16S rRNA was detected using qPCR. The 16S rRNA levels were correlated with gene expression. Although pretreatment with H₂O₂ before immersion in F. psychrophilum did not significantly alter the amount of bacteria found in the gill, the immune response was influenced: exposure to F. psychrophilum resulted in a negative correlation with expression of IL-17c1, MHC I and MHC II, while pretreatment with H₂O₂ resulted in a positive correlation with IL-4/13A and IgM. Exposure to either H₂O₂ or F. psychrophilum influenced the regulation of gene expression and damaged tissue. Exposure to both combined altered the immune response to infection and postponed healing of gill tissue.     

干旱对玉米过氧化氢、MDA含量及SOD、CAT活性的影响

不同抗旱性的玉米幼苗在水分胁迫下过氧化氢和MDA含量均增加,增加幅度与品种抗旱性呈负相关。SOD和CAT活性的变化表现出抗旱性品种增强,不抗旱品种降低的趋势,二者活力水平,尤其SOD活力与品种抗旱性呈正相关。     

棉籽油脱色中色泽和烟点以及过氧化值的变化

在棉籽油中添加不同用量的白土作脱色和复脱色试验，测定棉籽油脱色过程中色泽，烟点和过氧化值等几项指标的变化，发现在真空条件下，白土能有效地脱除过氧化物，且随着脱色次数的增加，烟点下降，过氧化值下降，黄色变浅，但蓝色与红色在第三次脱色时反而加深，此外，先用占油重３％的白土脱色，再用占油重２％的白土脱色，效果较佳。