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排序方式: 共有711条查询结果,搜索用时 15 毫秒
61.
为了分离纯化并鉴定市售草莓主要的腐败污染菌,分析筛选拮抗能力良好且具有较大生物防治潜能的酵母。通过菌落形态和显微形态初筛出主要腐败菌,并采用28S rDNA序列分析鉴定到属。针对典型腐败菌做对峙实验,筛选出有明显拮抗作用的酵母,26S rDNA序列分析鉴定到属种。酵母和腐败菌同时反接在有伤冬枣上,验证酵母拮抗能力,分析酵母作为生防菌的应用效果。本研究显示草莓携带的致腐败的微生物主要是空气中常见的5种霉菌为枝孢霉属(Cladosporium spp.)、灰葡萄孢菌(Botrytis cinerea)、链格孢属(Alternaria sp.)、毛霉(Mucor sp.)和白地霉(Geotrichum candidum)。从191株酵母中筛选出对腐败菌有拮抗作用的菌株23株,属于17种酵母,在体内体外实验中均表现出良好拮抗效果的酵母为美极梅奇酵母(Metschnikowia pulcherrima)S4-1。 相似文献
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Gelatin ceftiofur alkali microsphere was prepared to observe its characteristics and evaluate preservation conditions. The glutaraldehyde was increased and the carboxylic methyl chitosan was added to improve the microsphere. The experimental results show microspheres have a better morphology surface and fairly regular structure with 4% glutaraldehyde. The average particle size is 15.84 μm and particle size distribution is narrow which shows a good uniformity. Microsphere size was affected by the stirrer speed, dosing ratio and curing degree. The greater drug loaded is, the better microspheres loading is; but with the increase of drug loading rate, the entrapment efficiency increases first and then decreases. The drug release rate of the microsphere is 24.90% in 0.5 h and 84.90% in 48 h, when CMC-GMs with 4% curing agent is 32.03% in 0.5 h and 88.44% in 48 h. So Gms embedding of ceftiofur alkali are better than CMC-GM. The stability tests show that strong light, high temperature, high humidity have a great influence on the microspheres. 相似文献
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《Materials Letters》2005,59(14-15):1889-1892
Eutectic alloy Sn–9Zn is regarded as one of the potential substitutes for Pb-containing solders, although it has some drawbacks yet to overcome. One of the problems involved is drastic viscosity increase of rosin-based flux during soldering or storage. In the present work we investigated the role of ZnO in the viscosity transition of rosin. The results show that the viscosity transition is directly caused by the presence of ZnO in molten rosin and, at a certain temperature, there exists a critical ZnO concentration for its occurrence. The critical ZnO concentration increases with temperature. A graph is presented to show the conditions for the viscosity transition, in a ZnO concentration–temperature space. The transition is found to be reversible when shifting temperature or ZnO concentration across the boundary and to assume the features of a thermally activated phase transformation. 相似文献
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Eva Marcuzzo Donatella Peressini Frédéric Debeaufort Alessandro Sensidoni 《Innovative Food Science and Emerging Technologies》2010,11(3):451-457
Gluten films obtained in acid conditions display some protein dispersion difficulties. Ultrasound treatment (UT) could represent an interesting strategy for improving gluten film appearance. Different UT exposure times were applied to film-forming dispersion. The aim of this work was to investigate the effect of ultrasound treatment on gluten-based films at molecular and mesoscopic levels. Distribution in gliadin and glutenins was determined with SE-HPLC. The UT improved protein dispersion and final film appearance. Sonication did not lead to large changes in various gluten fractions, which suggests absence of important protein breakdown at the molecular level. Gluten showed high tolerance to UT. Surface properties of untreated and treated films were investigated by contact angle measurement: sonication promoted hydrophilic surface properties.Industrial relevanceBio-based packaging has been receiving increasing attention in view of its beneficial impact on the environment. Among proteins, gluten resulted as a very interesting film-forming material. Gluten films prepared in acid conditions showed problems in protein dispersion. Sonication represents a physical strategy which allowed us to obtain gluten-based films without the addition of chemical additives, such as sodium sulphite. 相似文献
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B-藻红蛋白是一种理想的生物光电材料.利用静电组装技术制备了聚二甲基二烯丙基氯化铵(PDDA)与B-藻红蛋白组装的多层复合薄膜.对薄膜的可见吸收光谱和荧光光谱进行了分析,结果表明:与B-藻红蛋白在溶液中的光谱特征相比,B-藻红蛋白在薄膜上的最大吸收峰由545 nm红移至553 nm,并在573 nm处产生了延迟荧光现象,且薄膜的最大吸光度和光致发射强度均与组装层数呈线性递增关系.随着薄膜组装层数的增加,倒置荧光显微镜能很好地观察到B-藻红蛋白在薄膜上出现明显的聚集体. 相似文献
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《Chemical engineering science》2004,59(22-23):5051-5060
A computational framework has been developed for the construction and evaluation of metabolic pathways given input substrates and knowledge of enzyme-catalyzed reactions. Application of the framework creates new and existing routes to both chemicals known to exist in biological systems and chemicals novel to biological systems. In the present application, we focus on biosynthetic routes to 7-carboxyindole, a specialty chemical currently produced by organic synthesis, using chorismate as a starting compound and the enzyme actions native to the biosynthetic route from chorismate to tryptophyan. Graph theory and its associated algorithms are exploited to represent molecules and perform enzyme-catalyzed reactions. Through repetitive application of the set of operators representing the enzymatic reactions of interest to the reactants and their progeny, reaction pathways are generated automatically. The concept of generalized enzyme function is introduced and defined as the third-level enzyme function (EC i.j.k) according to the four-digit transformations of the enzyme classification system (EC i.j.k.l). This concept maps enzyme-catalyzed reactions to transformations of functional groups and enables the generation of novel species and pathways. Thermodynamic properties are calculated using a group contribution method “on-the-fly” in order to provide one assessment of the relative feasibility of the novel pathways. 相似文献
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《Food microbiology》2004,21(1):33-42
There are a few reports on the antimicrobial activity of essential oils or their major constituents towards Shigella sp. The antimicrobial effect of basil and thyme essential oil and its major constituents thymol, p-cymene, estragol, linalool, and carvacrol was determined using the agar well diffusion assay. Thyme essential oil and thymol and carvacrol showed inhibition of Shigella sp. in the agar well diffusion method. The potential of thyme essential oil, thymol and carvacrol at 0.5% and 1.0% v/v for decontamination of lettuce was evaluated. A decrease of the shigellae was observed after washing with 0.5% while at 1% Shigella numbers dropped below the detection limit. However, the antimicrobial effect on a subsequent lettuce sample in the same decontamination solution was significantly decreased. In addition, application of thyme essential oil or thymol or carvacrol for decontamination is hampered by sensoric properties of the lettuce (browning, strong odour). 相似文献