Effect of Salinity on Hyphal Growth and Antimicrobial Potential of Two Halophilic Fungi

Halotolerant fungi possess the unique ability to survive and thrive in hypersaline environments, making them promising candidates for the production of bioactive secondary metabolites. This study investigated the effect of varying salinity levels (5–25% NaCl) on the growth, antimicrobial activity, and chemical profile of two halophilic fungal strains, Fusarium oxysporum RAS2 and Aspergillus niger RAS3, previously isolated from the Vellar estuary. Maximum hyphal growth for both strains was observed at 5% NaCl, whereas the highest antibacterial and antifungal activities were recorded at 20% NaCl. Ethyl acetate extracts from cultures grown at this concentration exhibited significant inhibition against Pseudomonas sp. and Candida albicans (F. oxysporum RAS2), and Pseudomonas sp. and Rhizopus sp. (A. niger RAS3). The chemical profile of the fungal crude extracts was studied extensively. These results suggest that salt-induced stress enhances the biosynthesis of potent antimicrobial compounds in halotolerant fungi, underscoring their potential as valuable sources of novel therapeutics.