Department of Food Science & Technology, Oregon State University , Corvallis, Oregon 97331-6602, United States.
J Agric Food Chem. 2013 Sep 18;61(37):8783-9. doi: 10.1021/jf4018965. Epub 2013 Sep 9.
The polymeric structure characteristics of β-chitosan from jumbo squid (Dosidicus gigas) pens and α-chitosan from shrimp shells during depolymerization by cellulase hydrolysis at different degrees of deacetylation (DDA) (60, 75, and 90%) were investigated by using Fourier transform infrared spectroscopy and X-ray diffraction. Antibacterial activity of β-chitosan against Escherichia coli and Listeria innocua was compared with that of α-chitosan at similar Mw and degrees of deacetylation (DDA) by studying inhibition ratio and minimal inhibition concentration (MIC) and was coordinated with the structural characteristics of the two forms of chitosan. β-Chitosan was more reactive to cellulase hydrolysis than α-chitosan due to its relatively lower crystallinity (CI) and loose crystal property, and the 75% DDA chitosan was more susceptible to cellulase than the 90% DDA ones with the 75% DDA of β-chitosan mostly reactive. Both forms of chitosan showed more inhibition against E. coli than against L. innocua, and no difference against L. innocua between the two forms of chitosan was observed. However, the two forms of chitosan exhibited different levels of antibacterial activity against E. coli, in which 75% DDA/31 kDa β-chitosan demonstrated significantly higher inhibition (lower MIC) than that of 75% DDA/31 kDa α-chitosan, whereas 90% DDA/74-76 kDa α-chitosan had a higher inhibition ratio than that of 90% DDA/74-76 kDa of β-chitosan. This result may be explained by the impact of the different structural properties between α- and β-chitosan on chitosan conformations in the solution. This study provided new information about the biological activities of β-chitosan, a bioactive compound with unique functionalities and great potential for food and other applications.
采用傅里叶变换红外光谱和 X 射线衍射研究了不同脱乙酰度（DDA）（60%、75%和 90%）下纤维素酶水解对巨型鱿鱼（Dosidicus gigas）笔和虾壳中α-壳聚糖的β-壳聚糖的聚合结构特征。通过研究抑制率和最小抑菌浓度（MIC），比较了具有相似分子量和脱乙酰度（DDA）的β-壳聚糖对大肠杆菌和无害李斯特菌的抗菌活性与α-壳聚糖的抗菌活性，并与两种形式的壳聚糖的结构特征相协调。β-壳聚糖的结晶度（CI）和晶体疏松性相对较低，因此对纤维素酶水解的反应性比α-壳聚糖高，75%DDA 壳聚糖比 90%DDA 壳聚糖更容易受到纤维素酶的影响，75%DDA 的β-壳聚糖反应性最强。两种形式的壳聚糖对大肠杆菌的抑制作用均强于无害李斯特菌，且两种形式的壳聚糖对无害李斯特菌的抑制作用无差异。然而，两种形式的壳聚糖对大肠杆菌的抗菌活性水平不同，其中 75%DDA/31 kDa β-壳聚糖的抑制作用（更低的 MIC）明显高于 75%DDA/31 kDa α-壳聚糖，而 90%DDA/74-76 kDa α-壳聚糖的抑制率高于 90%DDA/74-76 kDa 的β-壳聚糖。这一结果可以用α-和β-壳聚糖之间不同的结构特性对溶液中壳聚糖构象的影响来解释。本研究为具有独特功能和在食品及其他应用中具有巨大潜力的生物活性化合物β-壳聚糖的生物活性提供了新信息。
