酶催化魔芋葡甘聚糖的可控降解

ENZYME-CATALYZED CONTROLLABLE DEGRADATION OF KONJAC GLUCOMANNAN

魔芋葡甘聚糖 (KGM)是一种来自植物的天然高分子 .它具有优异的可生物降解性和生物相容性 ,并具有许多独特的生理和药理功能 .本实验首先测定了 β 甘露糖酶在不同条件 (温度、pH值、介质 )下的活性 ,发现 β 甘露糖酶在 5 0℃左右 ,pH 9 4附近 ,乙醇含量低于 5 %的水介质中具有较高的活力 ;而在pH 7 0以下 ,或温度低于 3 0℃ ,或加入 2 0 %乙醇的条件下均基本上失活 .在此研究基础上 ,探讨了 β 甘露糖酶催化KGM降解反应的规律 ,通过调节反应条件制备了一系列分子量不同的降解样品 ,并确定了KGM的分子量与特性粘数之间的关系为 :[η]=5 0 6× 1 0 - 4M0 754w ,使得酶催化KGM的可控降解成为可能 ,从而为深入研究KGM及其衍生物的结构与性能 。

Konjac glucomannan (KGM) is a natural polymer from a plant. It possesses excellent biodegradability, biocompatibility and many unique physiological and pharmacological functions. In this work the effects of various factors (i.e., temperatures, pH, medium) on the activity of P-mannanase was firstly studied. The results show that beta-mannanase possesses high activity in the aqueous medium (pH 9.4) containing enthanol less than 5% (V/V) at about 50degreesC and basically lose its activity in the medium with pH lower than 7.0 or containing enthanol more than 20% (V/V), or at temperatures lower than 30degreesC. Based on these results, the degradation reaction of KGM catalyzed by beta-mannanase and its affecting factors were investigated, and a series of KGM samples with different molecular weights was prepared by adjusting the reaction conditions. Moreover, the intrinsic viscosity ([eta]) and the weight-average molecular weight ( M) of the degraded KGM products were measured, obtaining the following equation: [eta] = 5.06 x 10(-4) M-w(0.714). This work makes it possible to realize controllable degradation of KGM by means of an enzyme-catalyzed reaction, thus laying a solid experimental and theoretical foundation for further studying the structure and properties of KGM and its derivatives, and developing new application fields of them.