Gao Liwei, Zhao Xinjie, Liu Meng, Zhao Xiangzhong
School of Food Sciences and Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China.
Polymers (Basel). 2022 Jul 26;14(15):3022. doi: 10.3390/polym14153022.
Paramylon from (EGP) is a polymeric polysaccharide composed of linear β-1,3 glucan. EGP has been proved to have antibacterial activity, but its effect is weak due to its water insolubility and high crystallinity. In order to change this deficiency, this experiment carried out carboxymethylated modification of EGP. Three carboxymethylated derivatives, C-EGP1, C-EGP2, and C-EGP3, with a degree of substitution (DS) of 0.14, 0.55, and 0.78, respectively, were synthesized by varying reaction conditions, such as the mass of chloroacetic acid and temperature. Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) analysis confirmed the success of the carboxymethylated modification. The Congo red (CR) experiment, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetry (TG) were used to study the conformation, surface morphology, crystalline nature, and thermostability of the carboxymethylated EGP. The results showed that carboxymethylation did not change the triple helix structure of the EGP, but that the fundamental particles' surface morphology was destroyed, and the crystallization area and thermal stability decreased obviously. In addition, the water solubility test and antibacterial experiment showed that the water solubility and antibacterial activity of the EGP after carboxymethylation were obviously improved, and that the water solubility of C-EGP1, C-EGP2, and C-EGP3 increased by 53.31%, 75.52%, and 80.96% respectively. The antibacterial test indicated that C-EGP3 had the best effect on () and (), with minimum inhibitory concentration (MIC) values of 12.50 mg/mL and 6.25 mg/mL. The diameters of the inhibition zone of C-EGP3 on and were 11.24 ± 0.15 mm and 12.05 ± 0.09 mm, and the antibacterial rate increased by 41.33% and 43.67%.
来自（EGP）的副淀粉是一种由线性β-1,3-葡聚糖组成的聚合多糖。EGP已被证明具有抗菌活性，但其水不溶性和高结晶度导致其效果较弱。为了改变这一缺陷，本实验对EGP进行了羧甲基化修饰。通过改变反应条件，如氯乙酸的质量和温度，合成了三种取代度（DS）分别为0.14、0.55和0.78的羧甲基化衍生物C-EGP1、C-EGP2和C-EGP3。傅里叶变换红外光谱（FTIR）、凝胶渗透色谱（GPC）和核磁共振（NMR）分析证实了羧甲基化修饰的成功。采用刚果红（CR）实验、扫描电子显微镜（SEM）、X射线衍射（XRD）和热重分析（TG）研究了羧甲基化EGP的构象、表面形态、结晶性质和热稳定性。结果表明，羧甲基化没有改变EGP的三螺旋结构，但破坏了基本颗粒的表面形态，结晶区和热稳定性明显降低。此外，水溶性试验和抗菌实验表明，羧甲基化后EGP的水溶性和抗菌活性明显提高，C-EGP1、C-EGP2和C-EGP3的水溶性分别提高了53.31%、75.52%和80.96%。抗菌试验表明，C-EGP3对（）和（）的效果最佳，最低抑菌浓度（MIC）值分别为12.50mg/mL和6.25mg/mL。C-EGP3对（）和（）的抑菌圈直径分别为11.24±0.15mm和12.05±0.09mm，抗菌率提高了41.33%和43.67%。
