Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan, ROC.
Department of Food Science, National Taiwan Ocean University, Keelung, Taiwan, ROC; Center for Marine Bioenvironment and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan, ROC.
Carbohydr Polym. 2015 Dec 10;134:74-81. doi: 10.1016/j.carbpol.2015.07.072. Epub 2015 Jul 26.
Six chitosans with molecular weights (MWs) of 300, 156, 72.1, 29.2, 7.1, and 3.3 kDa were prepared by cellulase degradation of chitosan (300 kDa) and ultrafiltration techniques. We examined the correlation between activity against Escherichia coli and Staphylococcus aureus and chitosan MW, and provided the underlying explanation. In acidic pH conditions, the chitosan activity increased with increasing MW, irrespective of the temperature and bacteria tested. However, at neutral pH, chitosan activity increased as the MW decreased, and little activity was observed for chitosans with MW >29.2 kDa. At pH 5.0 and 6.0, chitosans exhibited good water solubility and zeta potential (ZP) decreased with the MW, whereas the solubility and ZP of the chitosans decreased with increasing MW at pH 7.0. Particularly, low solubility and negative ZP values were determined for chitosans with MW >29.2 kDa, which may explain the loss of their antibacterial activity at pH 7.0.
六种相对分子质量（MW）分别为 300、156、72.1、29.2、7.1 和 3.3 kDa 的壳聚糖通过纤维素酶降解壳聚糖（300 kDa）和超滤技术制备。我们考察了壳聚糖 MW 与对大肠杆菌和金黄色葡萄球菌活性的相关性，并提供了潜在的解释。在酸性 pH 条件下，壳聚糖活性随 MW 的增加而增加，而与温度和测试的细菌无关。然而，在中性 pH 下，壳聚糖活性随 MW 的降低而增加，MW >29.2 kDa 的壳聚糖活性很小。在 pH 5.0 和 6.0 时，壳聚糖表现出良好的水溶性，Zeta 电位（ZP）随 MW 降低而降低，而在 pH 7.0 时，壳聚糖的溶解度和 ZP 随 MW 的增加而降低。特别是，MW >29.2 kDa 的壳聚糖具有较低的溶解度和负 ZP 值，这可能解释了它们在 pH 7.0 时抗菌活性丧失的原因。
