Author: Mariya Francis
Francis, Mariya, 2024 Screening and purification of antimicrobial compounds from Australian freshwater fungi and species identification, Flinders University, College of Medicine and Public Health
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Antibiotics are an indispensable component in the healthcare for the treatment of diseases caused by microorganisms. Unfortunately, inappropriate handling of antibiotics has contributed to the development of a growing global concern, antimicrobial resistance. Novel antibiotic compounds need to be unlocked to overcome this challenge. Within the various potential sources, fungi are a richer source and a highly diverse kingdom to discover novel antibiotic compounds. However, it is narrowly explored, and freshwater fungi are one among that underexplored groups. Therefore, the main objective of this study was to extract secondary metabolites from freshwater fungi growing on different media and investigate the antimicrobial properties to combat antimicrobial resistance. Fifteen freshwater fungi isolated from Australian freshwater habitat were cultured on potato dextrose agar (PDA), rice, mung bean, and barley. The secondary metabolites from fungal cultures were extracted with methanol and screened for antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans. The fungal strains (MRP13A, MRP5A, and MRP7A) that showed activity were chosen for upscaling the production of antimicrobial compounds through solid-state fermentation method on mung bean and PDA substrate. To obtain the purified antimicrobial compound, the crude extract from harvesting the fermentation cultures was separated with column chromatography. The structure of one of the purified compounds obtained from MRP5A and MRP13A was identified as an open chain sugar, arabinitol. The purified compound was also tested against three additional pathogenic bacteria and the compounds showed only activity against Methicillin-resistant S. aureus (MRSA). No corresponding activity was observed against tested Gram-negative bacteria. Additionally, these compounds also showed moderate to high temperature and pH stability. The project also involved the identification of 15 freshwater fungal strains by amplifying the internal transcribed spacer (ITS) region of the fungal genome. Species identification of majority of the fungal strains revealed the novelty of fungal species.
Keywords: Australian freshwater fungi, Fungal secondary metabolites, Extraction, Methanol, Antimicrobial activity, Solid-state fermentation, Mung bean, PDA, Thin layer chromatography, Bioautography, Column chromatography, Structure elucidation.
Subject: Biotechnology thesis
Thesis type: Masters
Completed: 2024
School: College of Medicine and Public Health
Supervisor: Prof. Melissa Brown