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Molecular Weight and Aggregation of erwinia gum in Aqueous Solutions

Chemical Research in Chinese Universities 2000年第2期16卷 156-162页

作者： ZHANG Lina XU Xiaojuan ZHU RongPing Iijima Hideki Wuhan Univ Dept Chem Wuhan 430072 Peoples R China Natl Res Ctr Certified Reference Mat Beijing 100013 Peoples R China Asahi Chem Ind Co Ltd Chem Technol Dept 4 Miyazaki 8828847 Japan

erwinia(E) gum is composed of glucose, fucose, galactose and glucuronic acid. The weightaverage molecular weights M w, numberaverage molecular weights M n and intrinsic viscosities[η] of the four fractions and the unfractionated E gum in aqueous solutions at desired temperatures were studied by light scattering, membrane osmometry, size exclusion chromatography(SEC) and viscometry. The experimental results prove that E gum formed aggregates in the aqueous solution at 25 ℃ and the aggregates were broken gradually with increasing temperature. The dissociation of the aggregates of E gum in the aqueous solution started at 36 ℃, and was completed at around 90 ℃. The [η] values of E gum and its fractions are much higher than those of the conventional polymers with the similar molecular weights, and decrease with increasing NaCl concentration.

关键词： erwinia gum Light scattering SEC Membrane osmometry Viscometry Molecular weight Aggregation

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RHEOLOGICAL BEHAVIOR OF erwinia gum IN AQUEOUS SOLUTION

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Chinese Journal of Polymer Science 1999年第6期17卷 557-561页

作者：张俐娜 Hideki Iijima Hiromichi Tsuchiya Department of Chemistry Wuhan University Wuhan 430072 China Chemicals Technology Department Ⅳ Asahi Chemical Industry Co. Ltd Miyazaki 882-0847 Japan Fourth Specialty Chemical Sales Department Asahi Chemical Industry Co. Ltd. Tokyo 100-8840 Japan

erwinia (E) gum, an extracellular polysaccharide, is composed of fucose, galatose, glucose and glucuronic acid. Its viscosity behavior was investigated by a low-shear-rate multiball viscometer and a rotational viscometer. Its weight-average molecular weight M-w and intrinsic viscosity [eta] in 0.2 mol/L NaCl aqueous solution were measured by light scattering method at 35 degrees C and viscometry at 25 degrees C and found to be 1.06 x 10(6) g/mol and 1050 mL/g, respectively, and its aggregates in aqueous solution were proved by gel permeation chromatography (GPC). These results indicated that E gum in water has exceedingly high viscosity and exhibits Binham fluid behavior, owing to its aggregation. The viscosity of E gum decreased with increasing temperature, and the turning point appeared at 38 degrees C for dilute solution and 80 degrees C for concentrated solution suggesting that the aggregates of E gum in water started to disaggregate under these temperatures. In addition, the aggregates can be disrupted by adding either acid or base. The experimental results indicated that the E gum is a good thickening agent, and its fluid behavior is similar to xanthan.

关键词： rheological behavior erwinia gum polysaccharide solution properties molecular weight aggregation

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