Depto. Físico-Química, Instituto de Química de São Carlos (IQSC) - USP, Av. Trabalhador São Carlense, 400, Caixa Postal 780, São Carlos, SP CEP 13560-970, Brazil.
Depto. Físico-Química, Instituto de Química de São Carlos (IQSC) - USP, Av. Trabalhador São Carlense, 400, Caixa Postal 780, São Carlos, SP CEP 13560-970, Brazil.
Food Res Int. 2019 Feb;116:737-744. doi: 10.1016/j.foodres.2018.09.005. Epub 2018 Sep 6.
Rhamnolipid (RL) biosurfactants have been studied as agents to control the growth of food pathogens however, to be successful applied as antimicrobial agent in food, is important to determine the effect of environmental conditions on RL activity. Once pH is a determinant factor to the development of microorganisms in food, we investigated the antimicrobial activity of RL under different pH values. The antimicrobial activity of RL against the Gram-positive pathogens L. monocytogenes, B. cereus and S. aureus was pH dependent and favored at more acidic conditions while the Gram-negative Salmonella enterica and E. coli (EHEC) showed resistance at all pH levels studied. Bacillus cereus was the most sensitive bacteria showing MIC of 19.5 μg/mL and eradication of the population was observed after 30 min with 39.1 μg/mL of RL. The sensitivity to RL was associated with reduction on cell surface hydrophobicity and cytoplasmic membrane damage. Scanning Electron Microscopy images evidenced the cell damage promoted by RL on sensitive strains. The pH is an important factor to be considered on developing RL-based strategies to the control of food pathogens.
鼠李糖脂（RL）生物表面活性剂已被研究作为控制食源性病原体生长的制剂，然而，要成功地将其作为抗菌剂应用于食品中，确定环境条件对 RL 活性的影响是很重要的。由于 pH 值是食品中微生物发育的决定因素，我们研究了 RL 在不同 pH 值下的抗菌活性。RL 对革兰氏阳性病原体单核细胞增生李斯特菌、蜡状芽孢杆菌和金黄色葡萄球菌的抗菌活性取决于 pH 值，并在酸性条件下更为有利，而革兰氏阴性的沙门氏菌和大肠杆菌（EHEC）在所有研究的 pH 值下均表现出抗性。蜡状芽孢杆菌是最敏感的细菌，其 MIC 为 19.5μg/mL，用 39.1μg/mL 的 RL 处理 30min 后即可观察到细菌数量被完全消除。对 RL 的敏感性与细胞表面疏水性的降低和细胞质膜损伤有关。扫描电子显微镜图像证明了 RL 对敏感菌株的细胞损伤作用。pH 值是在开发基于 RL 的控制食源性病原体策略时需要考虑的一个重要因素。
