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Microbiology and Biotechnology Letters


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Food Microbiology (FM)  |  Food Borne Pathogens and Food Safety

Microbiol. Biotechnol. Lett.

Received: April 27, 2022; Revised: May 26, 2022; Accepted: May 31, 2022

산성 pH 조건에서 차아염소산나트륨의 항균 활성 향상

Enhanced Antibacterial Activity of Sodium Hypochlorite under Acidic pH Condition

Hyeon-Bin Son, Won-Bin Bae, and Kwang-Hwan Jhee*

Department of Applied Chemistry, Kumoh National Institute of Technology, Gumi 39177, Republic of Korea

Correspondence to :
Kwang-Hwan Jhee,

Sodium hypochlorite (NaClO) is a disinfectant widely used in hospitals and food industries because of its antimicrobial activity against not only bacteria but also fungi and virus. The antibacterial activity of NaClO lies in the maintenance of a stable hypochlorous acid (HClO) concentration, which is regulated by pH of the solution. HClO can easily penetrate bacterial cell membrane due to its chemical neutrality and the antibacterial activity of NaClO is thought to depend on the concentration of HClO in solution rather than hypochlorite ions (ClO). In this study, we investigated the antibacterial activity of NaClO according to pH adjustment by means of time kill test and assays of Reactive Oxygen Species (ROS) and adenosine triphosphate (ATP) concentration changes before and after NaClO treatment. We also investigated that the degree of cell wall destruction through field emission scanning electron microscopy (FE-SEM). Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) exposed to 5 ppm NaClO at pH 5 exhibited 99.9% mortality. ROS production at pH 5 was 48% higher than that produced at pH 7. In addition, the ATP concentration in E. coli and S. aureus exposed to pH 5 decreased by 94% and 91%, respectively. As a result of FE-SEM, it was confirmed that the cell wall was destroyed in the bacteria by exposing to pH 5 NaClO. Taken together, our results indicate that the antibacterial activity of 5 ppm NaClO can be improved simply by adjusting the pH.

Keywords: Antibacterial activity, FE-SEM, hypochlorous acid (HClO), ATP, reactive oxygen species

Graphical Abstract

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