Biological Characterization and Metabolic Variations among Cell-Free Supernatants Produced by Selected Plant-Based Lactic Acid Bacteria

Wasim S M Qadi; Ahmed Mediani; Zalifah Mohd Kasim; Norazlan Mohmad Misnan; Norrakiah Abdullah Sani; Nur Hidayah Jamar

doi:10.3390/metabo13070849

Biological Characterization and Metabolic Variations among Cell-Free Supernatants Produced by Selected Plant-Based Lactic Acid Bacteria

Metabolites. 2023 Jul 13;13(7):849. doi: 10.3390/metabo13070849.

Authors

Wasim S M Qadi¹, Ahmed Mediani², Zalifah Mohd Kasim¹, Norazlan Mohmad Misnan³, Norrakiah Abdullah Sani¹, Nur Hidayah Jamar⁴

Affiliations

¹ Department of Food Science, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Malaysia.
² Institute of Systems Biology (INBIOSIS), Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Malaysia.
³ Herbal Medicine Research Centre, Institute for Medical Research, National Institutes of Health, Shah Alam 40170, Malaysia.
⁴ Department of Biology and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, UKM, Bangi 43600, Malaysia.

Abstract

The aim of this research was to assess the antibacterial and antioxidant properties as well as the variation in metabolites of the cell-free supernatant (CFS) produced by lactic acid bacteria (LAB) from local plants: Lactiplantibacillus plantarum ngue16, L. plantarum ng10, Enterococcus durans w3, and Levilactobacillus brevis w6. The tested strains exhibited inhibitory effects against pathogens, including Bacillus cereus, B. subtilis, Cronobacter sakazakii, Escherichia coli, Salmonella Typhimurium, and Staphylococcus aureus using the agar spot assay and well diffusion method. The CFS from all four strains displayed antibacterial activity against these pathogens with minimum inhibitory concentration (MIC) values ranging from 3.12 to 12.5 mg/mL and minimal bactericidal concentration (MBC) values ranging from 6.25 to 25.0 mg/mL. Moreover, the CFS demonstrated resilience within specific pH (3-8) and temperature (60-100 °C) ranges and lost its activity when treated with enzymes, such as Proteinase K and pepsin. Furthermore, the CFS exhibited antioxidant properties as evidenced by their ability to inhibit the formation of two radicals (1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) compared to the negative control, De Man, Rogosa, and Sharpe (MRS) broth. The use of proton-based nuclear magnetic resonance (¹H-NMR) spectroscopy revealed the presence and quantification of 48 metabolites in both the CFS and MRS broths. Principal Component Analysis (PCA) effectively differentiated between CFS and MRS broth by identifying the specific metabolites responsible for the observed differences. The partial least squares (PLS) model demonstrated a significant correlation between the metabolites in the LAB supernatant and the tested antibacterial and antioxidant activities. Notably, anserine, GABA, acetic acid, lactic acid, uracil, uridine, propylene glycol, isopropanol, serine, histidine, and indol-3-lactate were identified as the compounds contributing the most to the highest antibacterial and antioxidant activities in the supernatant. These findings suggest that the LAB strains investigated have the potential to be utilized in the production of functional foods and the development of pharmaceutical products.

Keywords: 1H NMR; antibacterial; antioxidant; lactic acid bacteria; metabolomics; probiotic.

Abstract

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