This study investigated the antimicrobial effect of hot water with citric acid against Escherichia coli O157:H7 biofilm on stainless steel (SS). Hot water (50, 60, or 70 °C) with 2% citric acid exhibited a synergistic bactericidal effect on the pathogen biofilm. It was revealed that hot water and citric acid combination induced sub-lethally injured cells. Additionally, mechanisms of the synergistic bactericidal effects of hot water with citric acid were identified through several approaches. In terms of biofilm matrix, hot water removes exopolysaccharides, a major component of extracellular polymeric substances (EPS), thereby increasing contact between surface cells and citric acid, resulting in a synergistic bactericidal effect. In terms of the cell itself, increased permeability of citric acid through cell membranes destructed by hot water promotes the inactivation of superoxide dismutase (SOD) in E. coli O157:H7, which induce synergistic generation of reactive oxygen species (ROS) which promote inactivation of cell by activating lipid peroxidation, resulting in destruction of the cell membrane. Therefore, it is interpreted that when hot water with citric acid is applied to E. coli O157:H7 biofilm, synergy effects on the biofilm matrix and cell itself have a complex interaction with each other, thus causing a dramatic synergistic bactericidal effect.

这项研究调查了柠檬酸热水对大肠杆菌的抗菌作用不锈钢（SS）上的O157：H7生物膜。含2％柠檬酸的热水（50、60或70°C）对病原体生物膜具有协同杀菌作用。揭示了热水和柠檬酸的组合诱导了亚致死性损伤的细胞。另外，通过几种方法确定了热水与柠檬酸的协同杀菌作用的机理。就生物膜基质而言，热水去除了胞外聚合物（EPS）的主要成分胞外多糖，从而增加了表面细胞与柠檬酸之间的接触，从而产生了协同的杀菌作用。就细胞本身而言，柠檬酸透过热水破坏的细胞膜渗透性增加，可促进大肠杆菌中超氧化物歧化酶（SOD）的失活。O157：H7可以诱导活性氧（ROS）的协同生成，从而通过激活脂质过氧化作用促进细胞的失活，从而破坏细胞膜。因此，据解释，当将柠檬酸热水加到大肠杆菌O157：H7生物膜上时，对生物膜基质和细胞本身的协同作用相互之间具有复杂的相互作用，从而引起戏剧性的协同杀菌作用。