Department of Food Science, National Ilan University, Ilan 26047, Taiwan.
Food Chem. 2012 Dec 15;135(4):2397-403. doi: 10.1016/j.foodchem.2012.06.122. Epub 2012 Jul 20.
Low molecular weight chitosan (LMWC) and nisin, recognized as cationic antibacterial agents (CAAs), inhibit bacterial growth by interacting with the anionically charged cell wall. In this study, alanine uptake significantly reduced the anionic cell surface charge, as determined by the zeta potential (ZP) measurements, of Staphylococcus aureus, resulting from the incorporation of d-alanine into the cell wall. Minimum inhibitory concentration (MIC) tests and growth inhibition curves revealed that LMWC and nisin possessed inverse antibacterial activity against three strains of S. aureus, depending on the strains' net charge. A twofold reduction in the MIC value of nisin was obtained against S. aureus, inoculated in a 1.0% d- or l-alanine-augmented trypticase soy broth medium. A flocculation test demonstrated that neutralizing the anionic surface charge using d-alanine reduced the adsorption of S. aureus onto LMWC. Furthermore, the reduced surface net charge could enhance the colonization capacity of S. aureus on glass.
低相对分子质量壳聚糖（LMWC）和乳链菌肽，被认为是阳离子抗菌剂（CAAs），通过与带负电荷的细胞壁相互作用来抑制细菌生长。在这项研究中，通过zeta 电位（ZP）测量发现，丙氨酸摄取显著降低了金黄色葡萄球菌的阴离子细胞表面电荷，这是由于细胞壁中掺入了 D-丙氨酸。最小抑菌浓度（MIC）试验和生长抑制曲线表明，LMWC 和乳链菌肽对三种金黄色葡萄球菌菌株具有相反的抗菌活性，这取决于菌株的净电荷。在添加 1.0% D-或 L-丙氨酸的胰蛋白酶大豆肉汤培养基中接种金黄色葡萄球菌时，乳链菌肽的 MIC 值降低了两倍。絮凝试验表明，使用 D-丙氨酸中和阴离子表面电荷会减少金黄色葡萄球菌吸附到 LMWC 上。此外，减少的表面净电荷可以增强金黄色葡萄球菌在玻璃上的定植能力。
