FMC BioPolymer AS/NovaMatrix, Industriveien 33, N-1337 Sandvika, Norway; Norwegian BioPolymer Laboratory, Department of Biotechnology, Norwegian University of Science and Technology, N-7034 Trondheim, Norway.
Norwegian BioPolymer Laboratory, Department of Biotechnology, Norwegian University of Science and Technology, N-7034 Trondheim, Norway.
Carbohydr Polym. 2008 Sep 5;73(4):656-64. doi: 10.1016/j.carbpol.2008.01.007. Epub 2008 Jan 17.
The kinetics and mechanisms of depolymerization of aqueous chitosan and alginate solutions at elevated temperatures have been investigated. Chitosan salts of different degree of acetylation (FA), type of counterions (-glutamate, -chloride) and degree of purity were studied. One commercially available highly purified sodium alginate sample with high content of guluronic acid (G) was also studied. Furthermore, the influence of oxygen, H(+) and OH(-) ions on the initial depolymerization rates was investigated. Depolymerization kinetics was followed by measuring the time courses of the apparent viscosity and the intrinsic viscosity. The initial rate constants for depolymerization were determined from the intrinsic viscosity data converted to a quantity proportional to the fraction of bonds broken. The activation energies of the chitosan chloride and chitosan glutamate solutions with pH close to 5 and the same degree of acetylation, FA=0.14, were determined from the initial rate constants to be 76±13kJ/mol and 80±11kJ/mol, respectively. The results reported herein suggest that the stability of aqueous chitosan and alginate solutions at pH values 5-8 will be influenced by oxidative-reductive depolymerization (ORD) as the primary mechanism as long as transition metal ions are presented in the samples. Acid - and alkaline depolymerization will be the primary mechanisms for highly purified samples.
已研究了升高温度下水溶性壳聚糖和海藻酸盐溶液的解聚动力学和机制。研究了不同乙酰化程度（FA）、抗衡离子类型（-谷氨酸盐、-氯化物）和纯度的壳聚糖盐。还研究了一种市售的具有高含量古洛糖醛酸（G）的高纯度海藻酸钠样品。此外，还研究了氧、H(+)和 OH(-)离子对初始解聚速率的影响。通过测量表观粘度和特性粘度的时间曲线来跟踪解聚动力学。从特性粘度数据确定初始解聚速率常数，该数据转换为与断裂键分数成比例的量。具有接近 pH5 和相同乙酰化程度（FA=0.14）的壳聚糖氯化物和壳聚糖谷氨酸溶液的初始速率常数的活化能分别为 76±13kJ/mol 和 80±11kJ/mol。本文的结果表明，只要样品中存在过渡金属离子，氧化还原解聚（ORD）将作为主要机制影响 pH 值为 5-8 的水溶胶的稳定性。对于高纯度的样品，酸解和碱解将是主要机制。
