一种新型微生物胞外多糖--结冷胶(gellan gum)

结冷胶是由革兰氏阴性菌Sphingomonas paucimobilis经有氧发酵所产生的细胞外多糖胶原凝胶剂.由于它具有良好的热稳定性、热可逆性、耐酸碱等优良特性,使它逐步取代其他类多糖在工业中的应用.结冷胶的这些潜在的优势使它的开发和研究具有广阔的前景.本文综述了结冷胶(Gellan Gum)的组成、结构和特性,生物合成途径,发酵生产及应用与展望.尤其对结冷胶的结构与特性及其发酵生产结冷胶的影响因素进行了详细的介绍.     

结冷胶发酵生产技术

结冷胶（Gellan Gum）是美国Kelco公司八十年代继黄原胶之后开发的食品微生物多糖之一，某些特性优于黄原胶，美国FDA和欧洲等国家都批准了结冷胶在食品中的应用。中国1996年也批准了结冷胶作为食品添加剂在食品中的应用。由于结冷胶可以在极低的用量下产生凝胶，在0．25％的使用量上就可以达到琼脂1．5％的使用量和卡拉胶1％的使用量的凝胶强度，现已逐步代替琼脂和卡拉胶在工业上的应用。结冷胶生产成本仅比黄原胶略高一些，而销价是黄原胶的两倍以上，高达34美元／公斤，有极高的商业利润和市场前景。     

结冷胶生物合成的研究进展

结冷胶是由少动鞘氨醇单胞菌产生的一种新型微生物多糖,具有用量低、透明度高、耐酸、耐高温、耐酶、兼容性好等优良特性,在食品、制药、化工等行业具有广泛的用途.本文综述了结冷胶发酵生产工艺,指出改善结冷胶的提取工艺是提高产量和质量的关键,并提出了从少动鞘氨醇单胞菌生理学方面来探索结冷胶生物合成及利用基因工程手段来提高结冷胶产量的新思路.     

结冷胶对面条品质的影响研究

通过对面条的蒸煮特性、质构特性、感官品质方面的测定和评价,考察了结冷胶对面条品质的影响及相关规律。结果显示:加入结冷胶之后,面条的断条率呈现出下降趋势,面汤的浊度和面条的蒸煮损失率先降低后升高,在600 mg/kg处出现拐点;随着结冷胶添加量的增加,面条的硬度、咀嚼性呈明显增大趋势,黏聚性和黏性与结冷胶的添加量大致呈现出负相关的趋势;感官实验发现,加入结冷胶可以有效改善面条的口感,结冷胶的添加量为600、1000 mg/kg时,面条的感官评价分数最高,分别为95. 1和95. 3。过量的结冷胶会使面条韧性太强,适口性变差。     

细菌胞外多糖的研究和应用

综述了已经工业化生产的黄原胶、结冷胶和热凝多糖的历史与现状，重点介绍了三种多糖的应用情况，以及乳酸菌胞外多糖的应用和研究现状，进一步展望了未来细菌胞外多糖的发展趋势和应用前景。     

微生物多糖结冷胶的分批发酵动力学模型

结冷胶是少动鞘脂单胞菌发酵生产的一种重要微生物胞外多糖,广泛应用于食品、制药等工业领域。文中深入研究了少动鞘脂单胞菌发酵高产结冷胶的发酵过程规律,建立了结冷胶发酵过程中菌体生长、产物积累和基质消耗的数学模型。计算结果表明:数学模型的模拟计算结果与实验值拟合性较好,平均误差在5%以内,较好地反映了结冷胶发酵过程中菌体生长、底物消耗和产物合成过程及其动力学机制。进一步利用该模型对不同初始糖质量浓度条件下底物消耗、菌体生长、结冷胶合成进行预测,实际结果与预测值误差小于10%,说明建立的模型具有较好的适用性,对结冷胶发酵生产过程具有实际指导意义。     

一种低黏度悬浮液体系的开发研究

为研发一种低黏度悬浮液体系,比较了结冷胶与K型卡拉胶、黄原胶、透明质酸、泊洛沙姆等溶液稳定剂互配在副干酪乳杆菌悬浮液中的应用,评价了这几种原料对溶液外观、口感、稳定性以及流变性能的影响。结果显示,加入0.03%以上结冷胶的溶液能够很好的悬浮副干酪乳杆菌,并且黏度很低,不会带来稠厚的口感,但流动性较差;而在结冷胶悬浮体系中加入适量透明质酸互配,能够形成流动性好、黏度低(η100 mPa·s)、口感清爽且能够悬浮副干酪乳杆菌的体系。使用结冷胶与透明质酸复配可以形成低黏度悬浮体系以满足各类产品的开发。     

魔芋葡甘聚糖与结冷胶协同相互作用及凝胶化研究

魔芋葡甘聚糖与结冷胶按一定比例共混得到凝胶,测定凝胶强度,并用红外光谱仪对多糖分子间的相互作用机理进行分析.当总糖浓度为1.0％（wt）,魔芋胶与结冷胶共混比例为40/60,制备温度为80℃,体系盐离子（Ca2＋）浓度为6.0 mmol/L时可得到协同相互作用最大值,这是多糖分子间相互作用,发生了聚合交联,产生了协同增效作用.     

植物蛋白黏合剂研究进展

系统地介绍了植物蛋白黏合剂的主要种类、改性方法、胶接机理及影响因素,并分析了当前植物蛋白黏合剂存在的问题,探讨了今后研究的主要方向,为其在胶合板行业中逐步替代"三醛胶"提供理论依据,同时也为促进植物蛋白资源的高质化利用提供重要参考。     

钠型结冷胶与乳酸链球菌素的接枝条件优化

以1-乙基-(3-二甲基氨基丙基)碳二亚胺盐酸盐和N-羟基硫代琥珀酰亚胺钠盐为交联剂,对乳酸链球菌素接枝钠型结冷胶的反应条件进行单因素法优化,并利用傅里叶变换红外光谱和抑菌时效性实验对接枝物进行表征。结果表明,乳酸链球菌素与钠型结冷胶的最佳接枝反应条件为:1-乙基-(3-二甲基氨基丙基)碳二亚胺盐酸盐和N-羟基硫代琥珀酰亚胺钠盐的摩尔比为2∶1、反应体系pH为6、反应体系温度为40℃、钠型结冷胶的活化时间为70 min、加入乳酸链球菌素后的反应时间为16 h。接枝率由纯化前的不足5.0%提升至14.5%,弱碱性条件下对枯草芽孢杆菌的抑菌时效性也由12 h延长至24 h。     

Gellan gum–O,O′‐bis(2‐aminopropyl)‐polyethylene glycol hydrogel for controlled fertilizer release

A gellan gum–Jeffamine superabsorbent hydrogel was obtained with different crosslink densities using different amounts of (1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide hydrochloride) and N‐hydroxysuccinimide. Infrared spectroscopy and thermal analysis confirm the crosslinking. A morphology analysis indicates denser structures for samples with higher crosslinking points. The swelling degree in high‐acyl gellan gum hydrogels was equivalent to 145 times their dry weight, and 77 times when low‐acyl gellan gum was used. Hydrogels also showed a 450 min water retention, as opposed to 280 min for pure water, evidencing good humidity control, suitable for use in arid climates. They also demonstrated a maximum release of commercial fertilizer of about 400 mg per gram for KH₂PO₄ and about 300 mg per gram for NPK 20‐5‐20. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45636.     

Gelcasting of alumina suspension using gellan gum as gelling agent

As one of the excellent colloidal ceramic forming methods for fabricating complex shaped ceramic components, gelcasting has been extensively investigated in the past two decades. In this article, a novel nontoxic system for gelcasting of ceramics was investigated using gellan gum as gelling agent. The rheological and gelling properties of gellan gum solutions with different types of cations and different concentrations of divalent magnesium ions were studied. Influences of concentration of gellan gum and solid loading of alumina suspension on the rheological properties and gelling properties of alumina suspension were investigated. The rheological properties of concentrated alumina suspension mixing with gellan gum and magnesium chloride were evaluated. Dense ceramics prepared by gellan gum gelation showed homogeneous microstructure and good mechanical properties.     

Effects of Microbial Polysaccharides on the Oil Absorption and Quality Characteristics of a Deep-Fried Snack Namkeen

This study investigates the potential of microbial polysaccharides (MP) gellan gum and pullulan to reduce oil uptake in a deep-fried snack (Namkeen). The concentration of MP in refined wheat flour varied between 1–10% (w/w) and the frying time and temperature are optimized. The results reveal that MP added namkeens showed a maximum relative oil reduction of 33.87% with gellan gum and 26.93% with pullulan at 10% (w/w). Gellan gum and pullulan result in oil reduction of 23.19% and 15.97% with 5% (w/w). The results reveal that gellan gum added namkeens exhibited 1.45 times lower oil uptake than pullulan added namkeen indicating potential oil reduction capabilities. The hardness of namkeen is observed to increase with an increase in MP concentration. Sensorial and textural characteristics of control and MP incorporated fried samples are comparable up to 5% (w/w) with MP concentration. The results for the control samples and MP incorporated samples are statistically significant. Furthermore, overall sensorial acceptability of pullulan added namkeens (7.74 ± 0.53) is slightly higher than that of gellan gum added namkeens (7.64 ± 0.36). Practical Application: Low-fat diet and functional foods are expected to help in managing the conditions of hyperlipidaemia. This study focuses on the potential of MP in reducing the oil content of deep-fried snacks. The efficacy of MP gellan gum and pullulan as functional ingredients for oil reduction in fried snacks demonstrates its aid in formulating low-fat foods thereby retaining sensorial characteristics.     

壳聚糖/结冷胶双层膜制备工艺优化及表征

以壳聚糖（CS）和结冷胶（GG）为原料，采用溶液流延法并结合层层自组装技术制备了CS/GG双层膜，通过单因素和响应面试验优化制备工艺条件，并对双层膜的微观形貌、化学结构、力学性能、光学性能、阻水性能和抗氧化性能进行评价。结果表明，CS质量分数1.7 %、GG质量分数1.5 %、CS与GG成膜液体积比4/6、甘油质量分数25 %条件下双层膜的拉伸强度为38.83 MPa、透湿量为750.76 g/（m²·d）；与单层膜相比，CS/GG双层膜表面光滑、截面致密，红外光谱分析结果表明双层膜具有良好的相容性；双层膜可以有效改善纯CS膜、纯GG膜的力学性能和阻水性能。     

Gellan gum capped silver nanoparticle dispersions and hydrogels: cytotoxicity and in vitro diffusion studies

The preparation of highly stable water dispersions of silver nanoparticles using the naturally available gellan gum as a reducing and capping agent is reported. Further, exploiting the gel formation characteristic of gellan gum silver nanoparticle incorporated gels have also been prepared. The optical properties, morphology, zeta potential and long-term stability of the synthesized silver nanoparticles were investigated. The superior stability of the gellan gum-silver nanoparticle dispersions against pH variation and electrolyte addition is revealed. Finally, we studied the cytotoxicity of AgNP dispersions in mouse embryonic fibroblast cells (NIH3T3) and also evaluated the in vitro diffusion of AgNP dispersions/gels across rat skin.     

Analysis of stability of food emulsions by Eyring's theory: Influence of different biopolymers

Eyring's kinetic theory of liquids was applied to the study of flow behavior of low oil content mayonnaises at different temperatures. These food emulsions were formulated with different biopolymers as stabilizers (polysaccharides such as modified starch, gellan gum, and pectin). The analysis of the values obtained for the parameters of the Eyring equation for viscosity determined the emulsion containing only starch as a stabilizer is the most unstable to stirring. Replacement of part of the starch with gellan gum or pectin enhances the stability of the emulsion. The results for activation energy are quite similar for high shear rates, which can be explained by the evolution of the average drop size distribution. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2653–2657, 2004     

Transport of Gellan Gum Microbeads in Soil Columns of Various Grain Size Distributions

The transport of gellan gum microbeads as potential cell carriers was investigated in horizontal columns packed with different grain size classes of gravel (2–16 mm) and sand (0.25–2 mm). A suspension of microbeads was pulsed into each column for 6 h, followed by injection of water for 42 h. In general, the total amount of microbeads travelling across a given section of the column increased with injection time but decreased towards the column outlet, varying as a direct function of grain size. The results of this study demonstrate the feasibility of the transport of gellan gum microbeads through medium sand to medium gravel across distances up to 110 cm.     

Cytotoxicity of sophorolipid-gellan gum-gold nanoparticle conjugates and their doxorubicin loaded derivatives towards human glioma and human glioma stem cell lines

Biocompatible gold nanoparticles were synthesized by using a naturally occurring gum--Gellan Gum--as a capping and reducing agent. These were further conjugated with sophorolipids which again were accessed through a biochemical transformation of a fatty acid. The cellular uptake of sophorolipid-conjugated gellan gum reduced gold nanoparticles and their cytotoxicity on human glioma cell line LN-229 and human glioma stem cell line HNGC-2 were investigated. Quite surprisingly even the simple sophorolipid-conjugated gellan gum reduced/capped gold nanoparticles showed greater efficacy in killing the glioma cell lines and, gratifyingly, the glioma stem cell lines also. The cytotoxic effects became more prominent once the anti cancer drug doxorubicin hydrochloride was also conjugated to these gold nanoparticles.