University of São Paulo (USP), São Carlos Institute of Chemistry (IQSC), Av. Trabalhador São Carlense, 400, CP-780, São Carlos, SP - CEP 13566-590, Brazil.
University of São Paulo (USP), São Carlos Institute of Chemistry (IQSC), Av. Trabalhador São Carlense, 400, CP-780, São Carlos, SP - CEP 13566-590, Brazil.
Food Res Int. 2024 Sep;192:114744. doi: 10.1016/j.foodres.2024.114744. Epub 2024 Jul 14.
The use of natural and sustainable additives, that are less aggressive to the environment, is a trend in the food industry. Rhamnolipids (RL) biosurfactants have shown potential for controlling food pathogens however, due to the presence of free carboxyl groups, the pH and ionic strength may influence the properties of such surfactants. In this study, we describe the antimicrobial activity of RL under different pH values and NaCl concentrations, towards both planktonic and biofilms of Listeria monocytogenes. RL were effective at pH 5.0 and the addition of 5 % NaCl improved the bactericidal efficacy for planktonic and sessile cells. The effect of NaCl was more pronounced at pH above 6 showing a significant increase in RL antimicrobial activity. At pH 7.0 planktonic population was eradicated by RL only when salt was present whereas biofilm viability was decreased by 5 log with MBIC varying from > 2500.0 mg/L (RL) to 39.0 mg/L (RL + 5 % NaCl). Larger vesicular and lamellar RL self-assembly structures were predominant when NaCl was present, suggesting their association with the antimicrobial activity observed. The pH and ionic strength of the medium are important parameters to be considered for the development of RL-based strategies to control L. monocytogenes.
使用对环境较温和的天然和可持续添加剂是食品工业的一种趋势。鼠李糖脂（RL）生物表面活性剂在控制食源性病原体方面显示出了潜力，然而，由于存在游离羧基，pH 值和离子强度可能会影响此类表面活性剂的性质。在这项研究中，我们描述了 RL 在不同 pH 值和 NaCl 浓度下对李斯特菌浮游生物和生物膜的抗菌活性。RL 在 pH 值为 5.0 时有效，添加 5%的 NaCl 可提高对浮游和固着细胞的杀菌功效。在 pH 值高于 6 时，NaCl 的影响更为明显，RL 的抗菌活性显著增加。在 pH 值为 7.0 时，只有在存在盐的情况下，RL 才能消灭浮游细胞，而生物膜的存活能力则降低了 5 个对数，MBIC 从 >2500.0 mg/L（RL）降至 39.0 mg/L（RL+5%NaCl）。当存在 NaCl 时，RL 主要形成较大的囊泡和层状自组装结构，这表明它们与观察到的抗菌活性有关。pH 值和离子强度是开发基于 RL 的控制李斯特菌策略时需要考虑的重要参数。
