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Int J Food Microbiol. 2018 Apr 20;271:24-32. doi: 10.1016/j.ijfoodmicro.2018.02.014. Epub 2018 Feb 14.

Metabolite profiling of Listeria innocua for unravelling the inactivation mechanism of electrolysed water by nuclear magnetic resonance spectroscopy.

Author information

1
Food Science and Technology Programme, c/o Department of Chemistry, National University of Singapore, Singapore 117543, Singapore; National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Suzhou, Jiangsu 215123, PR China.
2
The Nuclear Magnetic Resonance Laboratory, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
3
Food Science and Technology Programme, c/o Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.
4
Guangzhou Pulu Medical Technology Co., Ltd, Guangzhou, Guangdong 510800, PR China.
5
Science Research Programme, Temasek Junior College, Singapore 469278, Singapore.
6
Food Science and Technology Programme, c/o Department of Chemistry, National University of Singapore, Singapore 117543, Singapore; National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Suzhou, Jiangsu 215123, PR China. Electronic address: chmynghs@nus.edu.sg.

Abstract

Bactericidal effects of low concentration electrolysed water (LcEW) on microorganisms are previously well reported; however, the inactivation mechanism of EW is not understood. The lethal and sublethal injuries of L. monocytogenes and L. innocua by EW treatments were determined and the metabolic profile changes for L. innocua were characterised using nuclear magnetic resonance (NMR). Microbial metabolomics approach combined with multivariate data analyses was used to interpret the cellular chemical fingerprints of L. innocua. The relative amount of intracellular reactive oxygen species (ROS) was assayed using 2',7-dichlorodihydrofluorescein diacetate (H2DCFDA). The results showed that the proportion of the sublethally injured microbial cells L. monocytogenes and L. innocua increased from 40% to 70% and from 35% to 65%, respectively, when the free available chlorine (FAC) of LcEW increased from 2 to 8 mg/L. Overall, 36 low-molecular-weight metabolic compounds in L. innocua extracts were characterised by NMR spectroscopy. EW perturbation resulted in a drastic and multitude disruption across a wide range of biochemical process including peptidoglycan synthesis, nucleotides biosynthesis and amino acid metabolism. Elevated levels of α-ketoglutarate and succinate implicated the enhanced glutamate decarboxylase (GAD) system and γ-aminobutyric acid (GABA) shunt for the protection against oxidative stress. These findings provided the comprehensive insights into the metabolic response of Listeria to EW oxidative stress and can serve as a basis for better utilisation for sanitisation.

KEYWORDS:

Listeria monocytogenes; Metabolomics; NMR; Oxidative stress; Sanitiser

[Indexed for MEDLINE]

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