Screening and purification of antimicrobial compounds from Australian freshwater fungi

Author: Phung Hien Le

  • Thesis download: available for open access on 28 Jan 2024.

Le, Phung Hien, 2021 Screening and purification of antimicrobial compounds from Australian freshwater fungi, Flinders University, College of Medicine and Public Health

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Abstract

Antibiotics are essential for the prevention and treatment of infectious diseases. However, years of misuse of antibiotics have led to the emergence of antibiotic resistance. Therefore, there is an urgent need to find and introduce new antibiotics. Fungi are an important source of antibiotics, yet only a minuscule fraction has been recorded and studied for novel compounds. The freshwater fungi, especially, are understudied compared to other fungal groups. Therefore, this study aims to discover novel antimicrobial compounds from Australian freshwater fungi. Thirty-eight freshwater fungi strains were previously isolated from submerged wood from three locations in Australia. After screening them on agar and evaluating their ability to produce the antibiotic compounds in solid-state fermentation, and liquid fermentation, six strains with significant activity were selected, including MR153A, MR33A, MR119A, CT98B, SCC31A, and SCC45A. The extract of MR153A was active against a range of Gram-negative and Gram-positive bacteria, while the extracts of the other five were active against Gram-positive bacteria. The extracts also had weak activity against Candida and Saccharomyces. Notably, all six strains were active against MRSA. The crude extracts of MR153A, MR33A, and MR119A were separated with silica-gel column chromatography, and four antimicrobial compounds were purified, one each from the first two fungi and two from the latter. Their minimal inhibition concentration and minimal bactericidal concentration against nine pathogenic bacteria and yeasts were determined. The most active compounds were from MR119A with an MIC of 2 µg/mL against Staphylococcus aureus, Enterococcus faecalis, and MRSA. One compound from MR153A has been elucidated.

Keywords: Freshwater fungi, Antimicrobial compounds, Antimicrobial screening, Compounds purification

Subject: Biotechnology thesis

Thesis type: Masters
Completed: 2021
School: College of Medicine and Public Health
Supervisor: Chris Franco