菊粉果聚糖的保健功能及应用价值

菊粉果聚糖是从菊科植物块根中提取、纯化、水解及喷雾干燥出来的寡糖。该文阐述了菊粉果聚糖的理化性质、生理功能及应用价值,介绍了菊粉果聚糖在国内外的研究进展和发展趋势,对菊粉果聚糖作为一种双歧杆菌因子和糖类、脂肪等替代品的研究、应用成果作了概括,为今后的进一步研究起到引导与借鉴作用。     

菊糖及低果聚糖的代谢及生理特性

菊糖和低果聚糖是一类在人体上胃肠道不可消化，在大肠内发酵并产生低级脂肪酸，可促进双歧杆菌增殖和排便，低热值，高安性的果聚糖。本文对此作了综述。     

植物中特定果聚糖的合成研究进展

果聚糖,是由多种细菌和植物产生的一种果糖聚合物,是重要的储藏碳水化合物。菊苣是一个商业果糖生产作物。研究表明,果聚糖在菊苣体内的生物合成是难以控制的。特制果聚糖-具有所需的聚合物长度和连接类型的果聚糖,是原本非果聚糖积累植物引进果糖基转移酶基因的成功表达。文章较为系统地综述了果聚糖的生物合成及修改,特定果聚糖的合成,果聚糖的功能及应用前景等方面的研究进展。     

果聚糖蔗糖酶基因的克隆表达及酶学性质分析

将来源于解淀粉芽孢杆菌(Bacillus amyloliquefaciens)的果聚糖蔗糖酶(levansucrase)基因进行克隆,并将其在Escherichia coli BL21(DE3)中表达。对发酵产酶后的菌体进行破壁和离心,粗酶液经镍柱纯化后,进行酶学性质研究。结果表明,重组酶的水解酶活和转移酶活最适温度分别为45℃和40℃,最适pH分别为6.5和6.0。此外,果聚糖蔗糖酶的K_m和V_(max)分别为150.74mmol/L和21.23μmol/(mL·min)。最后,在pH 6.0、40℃条件下,果聚糖蔗糖酶催化反应12 h后,体系中果聚糖质量分数可达34.05%。     

酶水解-阴离子色谱法联用测定婴幼儿配方奶粉中果聚糖的总含量及平均聚合度

摘 要：目的 建立酶水解—离子色谱法测定婴幼儿配方奶粉中总果聚糖的分析方法。方法 通过酶水解将样品中的果聚糖水解成果糖、葡萄糖,以PA1阴离子交换柱分离,脉冲积分安培检测器进行检测果聚糖总含量,以果糖与葡萄糖产生的比例计算平均聚合度。结果 果糖、葡萄糖在0.25~25.0 mg/L范围内线性关系良好（R2>0.999）,果聚糖的回收率为96.9%~104.4%,方法检出限为195mg/kg,定量限为650mg/kg。实际样品测定中,日间的相对标准偏差（RSD,n=6）为1.15%~3.87%。结论 可用于婴幼儿配方奶粉中果聚糖的总含量及平均聚合度的测定方法。     

产果聚糖蔗糖酶重组枯草芽孢杆菌的构建及表达

果聚糖蔗糖酶能够将蔗糖和乳糖转化为具有益生元功能的低聚乳果糖。为了实现果聚糖蔗糖酶在重组枯草芽孢杆菌中的高效表达,将两种启动子比较并进行串联操作,确定生产果聚糖蔗糖酶的最佳启动子并对重组菌的生长条件进行探索。构建WB-PH、WB-P、WB-H、1A-PH、1A-P、1A-H六种重组枯草芽孢杆菌,其中WB-PH发酵酶活明显优于其他重组菌。研究生长条件对重组菌WB-PH产酶的影响,采用大豆蛋白胨作为氮源,果聚糖蔗糖酶的表达量明显增加,发酵过程中保持较高的溶氧水平也对产酶量有较大的提高。优化后的发酵酶活最高可达108.34 U/mL,相比优化前提高了25.92倍。     

荷兰培育出低热量糖转基因甜菜

荷兰科研人员最近利用基因工程技术,将甜菜中的蔗糖分子,转变为果聚糖分子,从而培育出了可生产低热量糖的转基因甜菜。这种甜菜有望为廉价大量生产果聚糖提供方便。据介绍,果聚糖是由果糖形成的聚合物链,不容易被人体内的酶所消化。现在,生产商主要是利用生化技术合成果聚糖或者从菊黄、洋姜之类的植物中分离果聚糖,由于生产成本较昂贵,植物中提取的量又小,所以果聚糖的庞大市场一直未能打开,而甜菜可大量生产蔗糖。为此,荷兰科研人员就将洋姜内可产生果聚糖的基因移植到甜菜上,希望能利用甜菜高效的生产机能制造出果聚糖。该基因将蔗糖分子…     

重组果聚糖蔗糖酶的发酵优化及应用

为了研究不同条件下重组短小芽孢杆菌产果聚糖蔗糖酶的最适条件以及利用重组酶转化蔗糖-乳糖制备低聚乳果糖的最适转化条件。以前期构建的产果聚糖蔗糖酶重组短小芽孢杆菌Brevibacillus brevis/pNCMO2-lsc作为菌种,通过单因素试验以及正交试验确定其最适产酶的发酵培养基为:葡萄糖20 g/L、氮源(工业酵母粉∶棉籽粉=2∶1,质量比)为40 g/L、CaCl_20.5 mmol/L,最适产酶温度30℃。在最优条件下发酵培养,果聚糖蔗糖酶的酶活可达62.1 U/mL,是优化前的3.69倍。利用该重组果聚糖蔗糖酶转化蔗糖-乳糖制备低聚乳果糖,在蔗糖和乳糖质量浓度均为200 g/L情况下,确定其最适转化条件:反应温度35℃,pH 6.0,加酶量为2 U/g底物,反应8 h后低聚乳果糖转化率可达39.1%。     

果聚糖的合成与利用

介绍了富有果聚糖的植物种类及利用蔗糖合成果聚糖的微生物。讨论了果聚糖的特性、菊粉与果聚糖的功能及其利用情况。     

溶液化学特性对果聚糖在聚偏氟乙烯膜上吸附的影响

活性污泥体系中存在产生果聚糖的诸多微生物,研究其在膜表面的吸附行为有利于控制膜生物反应器中的膜污染.结果表明,果聚糖在聚偏氟乙烯膜上的吸附可在60 min内达平衡.随溶液pH值的增大,果聚糖吸附量先降低后增加,在pH=7.0处取得最小值,为20 mg/m2.而吸附量随离子强度的变化趋势则是先增加后降低,在离子强度为0.004处取得最大值,为39 mg/m2.果聚糖在聚偏氟乙烯膜表面的吸附等温线遵循兰格缪尔方程,并给出了不同溶液化学条件的吸附自由能.果聚糖与聚偏氟乙烯膜之间的吸附可能受静电力和范德华力的共同作用,且吸附是可逆的.     

The apple and your eye: Visual and taste rank-ordered probit analysis with correlated errors

I look at data from an experiment in which people rank apples according to how they think they will taste. They are then blindfolded and rank how they actually taste. I estimate a multinomial rank-ordered probit model with correlated errors between the taste and visual rankings. I find that the errors for visual characteristics are correlated based on coloring, while the errors for taste are correlated based on sweetness and tartness. Allowing for correlation between the errors in the two regressions shows that, although people often misperceive apple taste based upon visual cues, they do so in systematic ways. People who prefer the looks of an apple they think to be tart (Granny Smith), will like the taste of other apples which are also tart but less well-known (Jonagold).     

Protection and Competition in the US Market for Textiles and Clothing

US textile manufacturers look on in trepidation at the prospect of a reduction in their tariff and quota protection. Their most immediate concern is with import penetration in the clothing market Have they got any intrinsic advantages and to what degree can they turn fashion changes and computerization to their advantage? How do they rate the competition from Asian countries? What strategies are they pursuing? Such questions are considered in this paper.     

p-进Haar正交函数系与p-进Franklin正交函数系

引入了ｐ－进Ｈａａｒ函数系和ｐ－进Ｆｒａｎｋｌｉｎ函数系,证明了它们都是［０,１］上完备的标准正交系,而且是空间Ｃ［０,１］的（广义）Ｓｃｈａｕｄｅｒ基。     

Identification of platinum and palladium particles emitted from vehicles and dispersed into the surface environment

Platinum, palladium, and rhodium are emitted from vehicle catalytic converters. Until now, the form of precious metal particles in road dust and urban waste has not been identified. This study has located, imaged, and analyzed these particles in road dust and gully waste. Two fragments of catalytic converter have been observed in road dust. They are 40-80 μm in size and covered in many minute particles (<0.3 μm) of either platinum with minor rhodium or palladium. One fragment identified in gully sediment is smaller, 25 μm in diameter, hosting only one attached particle of palladium with minor rhodium. As fragments are washed off roads they begin to disintegrate and the precious metals become detached. Also precious metal-bearing particles have been located in incinerated sewage ash including a 20 μm diameter cluster of <3 μm sized platinum particles that may be the remains of a catalytic converter fragment that has survived incineration. The form of these precious metal-bearing particles described here reveals that as they are dispersed from roads they are likely to be present predominantly as two particle sizes. Either they are attached to larger fragments of catalytic converter or they are released as individual detached tiny <0.3 μm to nanoparticle sizes.     

PowerBulder中控件TreeView和ListView的编程与应用

从编程角度分别介绍了PowerBuilder的控件TreeView和ListView的插入、删除和加入列表项的图片的方法及应用。指出了二者的区别：TreeView控件采用树形结构显示列表项之间的层次关系,而ListView控件则用于显示并列的列表项。二者都有增国、编辑、删除和重排列中的列表项等方法,并能以此引发相应事件的处理过程。     

糖醇与低聚糖

糖醇与低聚糖同属于营养型功能性甜味型，是食用糖的替代品，两者的构成元素一样，生理特性相似，但各自又具特点，用途大致相同，应用领域主要是无糖低甜少热的保健食品，及特殊群体专用食品，发展前景十分广阔，是值得关注的两大类产品。     

热激蛋白及其与果蔬的抗冷性关系

热激处理能够减缓果蔬采后低温贮藏时冷害的发生,热激蛋白的诱导是提高果蔬冷害耐受性机理中的一部分。本文介绍了热激蛋白及其与果蔬抗冷性关系的研究进展。     

Brief survey of EPA standard-setting and health assessment

The Environmental Protection Agency (EPA) promulgates standards for air pollutants and drinking water contaminants, as part of its mandate to protect public health and welfare. The Agency also assesses the health risks associated with hundreds of chemical substances, often developing quantitative toxicity and cancer potency benchmarks. This article compares EPA standards and benchmark values to those of other countries and other agencies. This includes the national ambient air quality standards (NAAQS), the national primary drinking water regulations (NPDWR), and benchmark values from the Integrated Risk Information System (IRIS). Results show that the NAAQS are generally comparable to or less strict than the air quality standards of other countries and international organizations. The NPDWR tend to be less strict than the water quality standards of other countries for inorganic chemicals, and they are more strict about as often as they are less strict for organic chemicals. Reference values for toxicity and cancer potency derived in EPA health assessments posted in the IRIS database are less stringentthan those of other agencies about as often as they are more stringent, and they are often identical. Revisions to these values more often than not made them less stringent. These results suggest that EPA's standards and quantitative health assessments are not out of line with those of other agencies and other countries.     

PE燃气管道、PE球阀在燃气工程中的推广应用

针对城市地下管线敷设中越来越多使用PE燃气管道、PE球阀和钢塑转换接头,通过自身设计及实践,它在防腐、施工和抗地质的强烈变化等方面与钢管及部件具有明显的优势,在燃气工程中得到普遍推广应用。