Dietary fibre of coconuts from a pacific atoll: Soluble and insoluble components in relation to maturity

Polysaccharide fractions were measured in coconuts at three stages of maturity, which corresponded to dietary usage in the Tokelau Islands of the South Pacific. Kernel was sequentially extracted with cold water (CW), hot water (HW) hot 0.5% ammonium oxalate (HOX), 1M H² SO⁴ and 72% H² SO⁴, and the monosaccharide compositions of the fractions determined. Total readily soluble fractions (CW+HW+HOX) were predominantly galactomannan, and decreased from 77% of the polysaccharide in the immature kernel to 8.8% of that in the mature kernel. Insoluble mannan increased during maturation to be the major polysaccharide component in mature kernel. This indicates that marked differences exist between the three stages of maturity examined, in the properties of their dietary fibre. The results suggest that in studies of diets in which coconut is a staple part, there is a need for careful definition of the coconut component with respect to maturity. Furthermore, they show the importance of using dietary fibre methods which are appropriate to the solubility characteristics of the indigestible polysaccharide.     

Analysis of the Structure and Biosynthesis of the Lipopolysaccharide Core Oligosaccharide of Pseudomonas syringae pv. tomato DC3000

Lipopolysaccharide (LPS), the major component of the outer membrane of Gram-negative bacteria, is important for bacterial viability in general and host–pathogen interactions in particular. Negative charges at its core oligosaccharide (core-OS) contribute to membrane integrity through bridging interactions with divalent cations. The molecular structure and synthesis of the core-OS have been resolved in various bacteria including the mammalian pathogen Pseudomonas aeruginosa. A few core-OS structures of plant-associated Pseudomonas strains have been solved to date, but the genetic components of the underlying biosynthesis remained unclear. We conducted a comparative genome analysis of the core-OS gene cluster in Pseudomonas syringae pv. tomato (Pst) DC3000, a widely used model pathogen in plant–microbe interactions, within the P. syringae species complex and to other plant-associated Pseudomonas strains. Our results suggest a genetic and structural conservation of the inner core-OS but variation in outer core-OS composition within the P. syringae species complex. Structural analysis of the core-OS of Pst DC3000 shows an uncommonly high phosphorylation and presence of an O-acetylated sugar. Finally, we combined the results of our genomic survey with available structure information to estimate the core-OS composition of other Pseudomonas species.     

牛蒡寡糖对黄瓜幼苗诱导抗病性的研究

利用浓度为1．0mg／ml、3．0mg／ml、5．0mg／ml、8．0mg／ml和10．0mg／ml的牛蒡寡糖对黄瓜幼苗离体诱导3d，并用5．0mg／ml的牛蒡寡糖对黄瓜幼苗离体诱导1～6d后，测定与抗病相关的防御酶活性；利用5．0mg／ml的牛蒡寡糖诱导黄瓜幼苗第1真叶3d后接种白粉病菌，调查黄瓜植株的病情指数。结果表明，与对照组相比，不同浓度的牛蒡寡糖对黄瓜幼苗均有诱导作用，能显著提高被处理叶片PAL、POD、PPO、SOD、CAT和壳多糖酶的活性，不同的酶活性达到最高水平时的诱导浓度略有差异。几种酶活性随诱导的时间进程呈现不同水平的动态变化趋势，其中POD活性的提高幅度最大，且一直呈上升趋势。第1真叶的处理组较对照组病情指数降低11．91％，同株未诱导的第2真叶处理组较对照组降低27．42％，说明牛蒡寡糖诱导了黄瓜幼苗对白粉病的系统抗性。     

四种酵母甘露聚糖合成与释放特性的比较

比较了产朊假丝酵母、毕赤酵母、面包酵母和啤酒酵母培养过程中细胞壁甘露聚糖的合成与释放特性。结果表明:四种酵母的甘露聚糖合成均为生长偶联型;不同类型酵母的甘露聚糖合成能力差异显著(p<0.05),合成能力最强的啤酒酵母细胞壁甘露聚糖含量最高可达0.62g/L发酵液,而合成能力最弱的毕赤酵母仅为0.47g/L发酵液。四种酵母的甘露聚糖最大释放量均出现对数生长中期,并且不同类型酵母释放效率差异较大,最高值毕赤酵母甘露聚糖释放量达到了0.27g/L发酵液,最低值啤酒酵母仅有0.15g/L发酵液。乙醇显著刺激四种酵母的甘露聚糖释放(p<0.05),其中对产朊假丝酵母的影响最显著且在5%乙醇浓度下,与对照相比,其甘露聚糖释放量和释放率分别大幅提高了152%和120%。      

从豆清水中提取大豆低聚糖的工艺研究

介绍了从豆清水中提取大豆低聚糖的工业化生产工艺,并对成品大豆低聚糖的基本性质进行了研究。实验选择高温离心分离法脱除豆清水中的蛋白质,温度选择90℃,脱除率达85.12%。选择电渗析法进行脱盐处理,脱除率达85.8%。使用粉末活性炭进一步进行脱色,采用单因素及正交实验对脱色工艺进行研究,最佳脱色工艺为活性炭用量0.3%,40℃下脱色35min,脱色率达83.71%,低聚糖保留率为80.41%。      

裂壶藻补糖发酵及糖氮代谢对产油的影响

为了探索裂壶藻(Schizochytrium limacinum)突变株生长及产油过程中对碳源和氮源的需求,本文对发酵各阶段的碳源和氮源利用变化情况进行测定,并设定五个在不同时期的补糖实验组进行研究,分别观测各组各时期生物量、油脂产量。结果表明,前96 h是裂壶藻生长的重要时期,生物量大幅度增长,在发酵144~168 h时,油脂产量达到最大,各组经发酵7 d收获总的藻体,对生物量、油脂产量、DHA含量和DHA产量进行综合测定,结果表明,在发酵120 h时进行补糖为最佳时期,且油脂产量及DHA产量相比于对照组分别高出18.80%和22.44%。当氮源耗尽时补糖不仅可以促进油脂的产生,而且对DHA的形成也是有利的。      

单糖及寡糖定量分析方法综述

单糖和寡糖大多是可溶性糖,在生物体内具储存能量、转移介质的作用;此外,单糖和寡糖可以充当结构物质和功能分子如糖蛋白的配基。因此,糖类化合物的分析在生命科学、食品科学、医药科学和农业科学等领域中具有极其重要的意义。本文通过对单糖及寡糖分析方法相关的文献进行追踪、整理分类,系统介绍了单糖及寡糖的主要分析方法,并对气相色谱法、高效液相色谱法、毛细管电泳法和高效阴离子交换色谱法等4种定量分析方法在食品、蔬菜、水果及药物中的定量分析应用进行了分析评述,得出高效液相色谱-蒸发光散射法为定量分析单糖及寡糖较适宜的方法,期望为后期单糖及寡糖的定量分析研究提供一定的参考。      

发酵法生产魔芋葡甘聚糖酶的研究

目的：探索发酵生产葡甘聚糖酶的最佳条件。方法：在摇瓶培养的基础上，比较不同温度、pH和接种量对发酵反应的影响，并在5L发酵罐上用正交试验筛选最佳的产酶条件配伍。结果：该菌产生葡甘聚糖酶的最佳条件为温度50℃，pH5．5～6．0，接种量10％，发酵前期搅拌速度50rpm，通气量20L／h，6h后搅拌速度改为100rpm，通气量10L／h，在这个条件下发酵获得的酶比活力为4812U／mg，总活力达到7810U／mL。培养8h后细菌生物量、产物含量迅速提高，24h达到顶峰时期。发酵动力学属于偶联型。     

Recent advances refining galactooligosaccharide production from lactose

The production of prebiotic galactooligosaccharides (GOS) by the β-galactosidase catalysed conversion of lactose has become commercially important. Yet it remains a challenge to sufficiently understand the structure and activity of β-galactosidase, to increase the efficiency of transgalactosylation and GOS production and to improve the quality of GOS products in a rational way. This review covers the broad but related aspects of GOS synthesis including: the structure and reaction mechanism of β-galactosidase, factors effecting yield and productivity of GOS synthesis systems, the structure of GOS products, models for the kinetics of GOS synthesis and reactor configurations for GOS synthesis. It aims to couple recent discoveries with established knowledge to enhance understanding of the complex biochemistry of GOS synthesis.     

功能性低聚糖--水苏糖

水苏糖作为一种新兴的功能性低聚糖类 ,其开发和应用日益受到重视。本文介绍了水苏糖的性质、生理功能、制备方法及应用 ,并对其开发应用前景进行了展望。