酶解棕榈粕制备甘露寡糖及其组分的结构确定

以棕榈粕为底物,用中性β-甘露聚糖酶降解得到甘露寡糖粗品,并对其采用纸层析法分离纯化其中的各组分,最终得到甘露二糖、甘露三糖和甘露四糖三种寡糖组分.通过气相色谱(GC)检测可知,这三种寡糖中只含有甘露糖和葡萄糖.且甘露糖和葡萄糖的比例依次为1.9:1、3.8:1和3.8:1.采用基质辅助激光解析电离飞行时间质谱(MALDI-TOF-MS)测定分离得到的三种寡糖的结构.     

薄层层析-图像分析定量热凝胶β-1，3-葡寡糖

单向两次薄层层析展开可以显著提高对热凝胶β-1,3-葡寡糖的分析效果,以Silica gel60 F254硅胶板为固定相,V(乙酸)∶V(乙酸乙酯)∶V(水)=2∶2.4∶1.4为展开剂,展距20 cm时,单向两次展开可以较好地分离聚合度为2~13的热凝胶β-1,3-葡寡糖。此外还建立了Image J软件图像分析定量热凝胶β-1,3-葡寡糖的方法,在不同糖质量浓度范围(0.02~0.1、0.1~0.8、0.8~5.0 g/L)内寡糖显色斑点的灰度积分响应值与糖浓度分别有着很好的线性关系(R20.99)。该方法的灵敏度高达0.02 g/L,相对标准偏差为1%~5%,稳定性很好。与HPLC等方法相比具有操作简便、分析快速、不需专门仪器和特定寡糖标准品等优点。     

特定聚合度区间壳寡糖的膜分离制备技术

为了制备特定聚合度范围的壳寡糖(Chitooligosaccharides,COS),本研究探索了物料浓度、温度和跨膜压差(transmembrane pressure,TMP)条件对1000 Da纳滤膜分离壳寡糖混合物过程的影响,并针对连续渗滤过程,建立了壳寡糖收率和纯度预测的数学模型。结果表明,料液浓度70 g/L、温度45℃和跨膜压差15 bar为最佳分离条件。在最佳条件下,通过连续渗滤和纳滤浓缩过程处理壳寡糖混合物,获得了以聚合度(Degree of polymerization,DP)2~5为主的壳寡糖,纯度和收率分别为82.1%和42.1%,并利用数学模型成功预测了聚合度2~5壳寡糖的收率和纯度。本研究建立了一种基于纳滤膜分离的聚合度2~5壳寡糖的制备方法,为壳寡糖的功能研究和应用开发提供了基础。     

壳寡糖及其磷酸化修饰产物对小鼠脾淋巴细胞增殖及诱生细胞因子的影响

目的:研究壳寡糖及其磷酸化修饰产物对小鼠脾淋巴细胞增殖及诱生细胞因子的影响。方法:采用四甲基偶氮唑盐(MTT)法检测壳寡糖及其磷酸化修饰产物在不同质量浓度条件下对小鼠脾淋巴细胞增殖的影响;用酶联免疫吸附实验(ELISA)法测定白介素2(IL-2)和γ干扰素(IFN-γ)的含量。结果:壳寡糖及其修饰产物对小鼠脾细胞均具有明显的细胞增殖作用,并存在一定的剂量依赖关系,2种实验药物均能提高IFN-γ水平;IL-2测定结果显示,壳寡糖具有明显提高脾细胞分泌IL-2的作用。结论:壳寡糖及其修饰产物具有明显的免疫增强作用,该作用与诱导小鼠脾细胞增殖、提高脾细胞中IFN-γ、IL-2的水平有关。     

壳寡糖防止苹果果汁褐变的机理

以红富士苹果为材料,分别测定不同质量浓度壳寡糖(OCS)对果汁中自由基的清除作用,对超氧化物歧化酶(SOD)、谷胱甘肽过氧化酶(GSH-Px)、过氧化物酶(POD)、过氧化氢酶(CAT)4种抗氧化酶酶活性和多酚氧化酶(PPO)酶活性以及与抗氧化有关物质(还原型VC和总酚)含量的影响。结果表明:壳寡糖对果汁中自由基的清除作用比较明显,尤其在2mg/mL和4mg/mL的质量浓度条件下可以较好的抑制O2-.的产生。壳寡糖可以明显提高抗氧化酶的酶活性,并且降低PPO的酶活性。壳寡糖对果汁中还原型VC和多酚含量的变化无显著性影响。提示壳寡糖可以提高抗氧化酶的活性,降低果汁中自由基的含量,抑制PPO的酶活性,从而抑制苹果果汁加工中褐变的发生。     

海藻酸寡糖的纯化及分子量测定

通过酶解法制备出海藻酸寡糖粗品,采用Q Sepharose FF离子交换柱层析对寡糖进行分离纯化获得AS1和AS2,分别用凝胶层析法和乌式黏度法测定其相对分子质量。结果表明,凝胶层析法更适合寡糖分子量的测定,SA1和SA2的相对分子量为别为1.0×10~4Da、5.8×10~3Da。为海藻酸寡糖的进一步研究及开发提供了科学依据。     

基于分子模拟的壳寡糖-金属配合物的结合模式分析

目的:探讨壳寡糖分子与金属离子之间的相互作用。方法:在构建壳寡糖分子结构基础上,将相同数量壳寡糖分子与Fe2+/Zn2+/Mg2+离子混合,进而采用分子动力学模拟法,分析壳寡糖与金属离子之间的配位结合模式。结果:每个金属离子与1～2个壳寡糖分子相结合,而每个壳寡糖结合Fe2+、Zn2+和Mg2+数量分别为2.37,2.22和2.21个。金属离子在壳寡糖分子上的结合位点,主要为氨基中氮原子(N,N1和N2)和羟基中氧原子(O1,O2,O3,O6,O7,O10,O11和O12),而基本不与醚氧原子(O,O4,O5,O8)发生配位结合。在壳寡糖与金属离子混合体系中,主要存在壳寡糖与金属离子以1∶1和2∶1的两种配位模式,进而形成"悬挂"和"桥式"两种典型特征结构。壳寡糖与3种金属离子反应产物的稳定性,依次表现为Zn2+Fe2+Mg2+。结论:动力学模拟与文献报道(光谱研究)结果相一致,其可作为研究金属配合物结构、糖分子与金属离子的作用机制提供重要参考。     

基于2种衍生化方法对牛乳中寡糖的高效液相色谱-质谱联用分析

利用Sep-Pak C_(18)柱和石墨化碳柱对已脱脂和除去蛋白质的牛乳进行分离纯化,并采用1-苯基-3-甲基-5-唑啉酮(3-methyl-1-phenyl-2-pyrazolin-5-one,PMP)和2-氨基吖啶酮(2-aminoacridone,AMAC),2种衍生化试剂对其进行衍生化处理,通过高效液相色谱进行优化,AMAC衍生化的结果(约有67个峰)明显优于PMP衍生化的结果(约20个峰),最终确定AMAC为最佳衍生化试剂,并利用最终优化好的高效液相色谱条件,采用高效液相色谱-串联离子阱飞行时间质谱对牛乳中寡糖进行测定,最终测得7种乳寡糖并获得该7种乳寡糖的单糖组成。     

酶法制备魔芋甘露寡糖和产物分析

利用β-甘露聚糖酶水解20％魔芋粗粉制备魔芋甘露寡糖并对其产物进行成分分析.在工艺研究中对反应的pH值、温度、酶添加量、时间等进行单因素试验,确定最佳工艺条件为酶添加量为250IU/g,pH值6.5,45℃条件下,酶解50min,寡糖得率为35％.魔芋甘露寡糖的粗产物经硅胶薄层层析(TLC)分离表明,三糖、四糖含量较大.     

低聚合度壳寡糖制备及其组分的色谱行为分析

利用壳聚糖酶水解壳聚糖,再通过乙醇沉淀法制备低聚合度(Dp＜6)的壳寡糖.利用Shodex NH2P-50 4E色谱柱,以乙腈-氨水为流动相梯度洗脱,建立了一种分离度好、灵敏度高的壳寡糖HPLC分析方法;利用UPLC-MS定性鉴定壳寡糖中N-乙酰化的组分.研究还探讨了壳寡糖组分的色谱行为,发现壳寡糖的N-乙酰化是导致壳寡糖不按照聚合度大小进行色谱分离的主要原因,为壳寡糖质量分析、组分分离提供了依据.     

Oligosaccharide production by hydrolysis of polysaccharides: a review

Oligosaccharides are carbohydrates with a low molecular weight, which, when nondigestible, can produce bifidogenic activity and several other effects to human health. Oligosaccharides can be found naturally in foods or are produced by the synthesis from disaccharide substrates or by the hydrolysis of polysaccharides. Although it has yet to be improved, the hydrolysis of polysaccharides is the best choice for oligosaccharide production on a large scale, due to its reproducibility and smaller cost. This review concisely presents the main processes for the production of oligosaccharides by depolymerisation of polysaccharides (enzymatic, acid, and physical hydrolysis), taking into account their advantages, disadvantages, and perspectives.     

功能食品配料——低聚乳果糖

功能性低聚糖是由2－10个相同或不同的单糖以糖苷键结合而成,不被胃酸及酶降解,即一般所说的不消化糖类^[1]。功能性低聚糖具有某些独特的生理功能^[2],是一种重要的功能性食品配料。低聚糖在日本发展较早,并消费量近5万t。我国自90年代研究开发,“九五”期间年产已达万t以上,但主要品种只有氏聚异麦芽糖,低聚果糖,大豆低聚糖形成规模生产,低聚半乳糖,低聚乳果糖等尚属空白。本重点介绍低聚乳果糖的合成,功能和应用。     

寡糖对向日葵锈菌侵染的影响

为了明确寡糖对向日葵锈菌侵染的影响,在向日葵苗期用寡糖处理,观察接菌后锈菌夏孢子的萌发率和侵入率以及向日葵叶片的气孔开闭,并用甲苯胺蓝染色法对入侵位点酚类化合物的积累进行了检测。试验结果表明,与对照相比寡糖处理后锈菌夏孢子的萌发率和侵入率显著降低,而气孔关闭率显著升高。同时,在接种后12h时,大量的侵入位点产生了酚类化合物的积累,说明寡糖处理可以有效抑制向日葵锈菌的侵染。     

羊乳低聚糖超高效液相色谱-质谱鉴定中样品前处理方法及液相色谱条件优化

通过Sep-Pak C18与石墨化碳柱法、超滤法、透析法和葡萄糖凝胶层析法4 种不同的前处理方法,以离子交换色谱法检测乳糖的去除率和低聚糖的损失率为评价指标,最终确定葡聚糖凝胶层析法为最优前处理方法。然后,采用超高效液相色谱-串联Q-Exactive Focus质谱对羊乳中的低聚糖进行分析及结构鉴定,以低聚糖的总离子流图为评价指标,对液相洗脱条件进行优化,最终优化条件为：0～20 min,95%～78% A（乙腈）;20～35 min,78%～73% A;35～38 min,73～62% A;38～45 min,62%～50% A。结果显示,采用凝胶层析法前处理样品测得低聚糖种类显著高于未去除乳糖的样品,在最优液相色谱分离条件下,羊乳低聚糖中同分异构体得到较好分离,对羊乳中低聚糖的结构解析具有重要参考价值。     

Structural characteristics of oligosaccharides from soy sauce lees and their potential prebiotic effect on lactic acid bacteria

Oligosaccharides have attracted much attention due to the beneficial health effect on human beings. Oligosaccharides were extracted from soy sauce lees (SSLO) and were purified in this work. It was a mixture of oligosaccharides, which accounted for 80.5% of the total weight, and free monosaccharides. Only two monosaccharides, xylose and mannose, were detected in the molecular chain of SSLO. Their relative molar percentages were 53.2% and 46.8% for the oligosaccharide and monosaccharide fractions, respectively. A dose-dependent behaviour was observed for the growth promoting effect of SSLO on Lactobacillus bulgaricus and Streptococcus thermophilus. When 200 μg/ml of SSLO was applied, the L. bulgaricus concentration was 15.7-fold higher than the control, whilst the S. thermophilus concentration was 34.7-fold higher than the control. The analysis of DPPH radical scavenging activity indicated poor antioxidant activity of SSLO. It also suggested that the prebiotic effect was not correlated with antioxidant activity.     

Enzymatic synthesis of galacto-oligosaccharides and other lactose derivatives (hetero-oligosaccharides) from lactose

Non-digestible oligosaccharides are applied as functional food ingredients to replace sucrose and to exploit specific biological functions, particularly low cariogenicity, low caloric content, prebiotic activity, and their ability to prevent adhesion of pathogens and toxins to eukaryotic cells. Oligosaccharides derived through enzymatic synthesis from lactose, i.e., galacto-oligosaccharides, lactulose and lactosucrose, account for a major part of the annual oligosaccharide production. Enzymatic production of oligosaccharides employs lactose as galactosyl-donor to transfer the galactosyl-moiety of lactose to suitable acceptor carbohydrates through the activity of β-galactosidases, or employs lactose as a galactosyl-, glucosyl- or fructosyl-acceptor through the activity of β-galactosidases, glucansucrases and fructansucrases. This communication provides an overview on the structural diversity of galacto-oligosaccharides and hetero-oligosaccharides that are produced by enzymatic conversion of lactose, and reviews the strategies used to optimize enzymatic transglycosylation with lactose as glycosyl donor or glycosyl acceptor.     

Effect of low molecular weight dextrins on gelatinization and retrogradation of starch

!-Amylases, usually added to bread recipes as anti-firming agents, are known to produce low molecular weight dextrins by starch hydrolysis. The influence of these compounds on the gelatinization and retrogradation of starch was studied by differential scanning calorimetry. Adding oligosaccharides to starch caused a delay in gelatinization, although its extent was not quantified. However, oligosaccharides of degrees of polymerization (DP) 3-5 reduced the enthalpy of the retrogradation endotherm, shown as the staling endotherm. The addition of gluten to starch and starch/oligosaccharide mixtures had no effect on the gelatinization and retrogradation of starch. The retrogradation of starch in dough samples was also analysed, after 'baking' in the calorimeter, to obtain additional information about starch retrogradation during storage. Oligosaccharides of DP 3-5 also reduced the enthalpy of the retrogradation endotherm. This work provides evidence that oligosaccharides influence starch changes during the baking and storage of bread. These effects could be considered as the mechanism by which the bacterial !-amylase reduces starch retrogradation and acts as an anti-firming agent.     

海洋寡糖的生物活性研究进展

寡糖是具有2～10 个单糖残基通过糖苷键连接起来的直链或含分支链的糖类化合物,对人体健康有诸多益处,还具有甜味剂功能和特性,集营养、保健、食疗于一体。相较于多糖,寡糖还具有生物活性强、利于机体吸收等优点。近年来,海洋来源的寡糖被证明具有多种生物活性,包括抗氧化、抗肿瘤、抗炎、抗菌、抗凝血和提高免疫力等,可以广泛应用于食品、医药、化妆品、农业和水产等领域。本文介绍了4 种主要的海洋寡糖,包括几丁寡糖/壳寡糖、褐藻胶寡糖、琼胶寡糖和卡拉胶寡糖,简述其来源、结构特征、各种生物活性及应用,以期为海洋多糖资源的高价值利用及海洋寡糖的深度开发提供参考。     

Nondigestible oligosaccharides

Dietary carbohydrates range in molecular size from simple sugars to complex polymers with a degree of polymerization (DP) of up to 100,000 or more. Oligosaccharides are generally defined as carbohydrates from 2 to 20 monomeric units long. Oligosaccharides have been dietary staples since antiquity but have received much less attention than other carbohydrates such as simple sugars or dietary fiber. Recently, interest in oligosaccharides has increased not only because of properties that include sweetening ability and fat replacement, but also because of resistance to digestion in the upper gastrointestinal tract and fermentation in the large bowel. Thus, some oligosaccharides have functional effects similar to soluble dietary fiber such as enhancement of a healthy gastrointestinal tract, improvement of glucose control, and modulation of the metabolism of triglycerides. These oligosaccharides are the nondigestible oligosaccharides. These compounds are easily incorporated into processed foods and hold much promise as functional ingredients in nutraceutical products.     

Inulin Potential for Enzymatic Obtaining of Prebiotic Oligosaccharides

Oligosaccharides have been marketed since the 80s as low-calorie agents and recently have gained interest in the pharmaceutical and food industry as functional sweeteners and prebiotic enriching population of Bifidobacteria. Currently, they have an approximated value of $200 per kg and recently, inulin has been proposed as a feedstock for production of oligosaccharides through selective hydrolysis by action of endoinulinase. High optimum temperature (60°C) and thermostability are two important criteria that determine suitability of this enzyme for industrial applications as well as enzyme cost, a major limiting factor. Significant reduction in cost can be achieved by employing low-value and abundant inulin-rich plants as Jerusalem artichoke, dahlia, yacon, garlic, and onion, among others. In general, the early harvested tubers of these plants contain a greater amount of highly polymerized sugar fractions, which offer more industrial value than late-harvested tubers or those after storage. Also, development of recombinant microorganisms could be useful to reduce the cost of enzyme technology for large-scale production of oligosaccharides. In the case of fungal inulinases, several studies of cloning and modification have been made to achieve greater efficiency. The present paper reviews inulin from vegetable sources as feedstock for oligosaccharides production through the action of inulinases, the impact of polymerization degree of inulin and its availability, and some strategies to increase oligosaccharide production.