Bioprospecting of an Antarctic Pseudogymnoascus Isolate for Antibacterial and Antioxidant Activities

Abstract

Antarctic environments harbour cold-adapted microorganisms with considerable potential for the production of bioactive secondary metabolites. In the present study, a culturable Pseudogymnoascus sp. was isolated from soil collected near the Bharati Research Base, Antarctica, and evaluated for its antibacterial and antioxidant potential. The fungal isolate was morphologically characterized and cultivated at 20 ± 2 °C, followed by sequential extraction using methanol, ethyl acetate, and hexane. The methanolic, ethyl acetate, and hexane extracts showed crude extract recoveries of approximately 0.67, 0.61, and 0.57 mg/mL, respectively. Among the extracts, only the methanolic fraction exhibited detectable antibacterial activity against the tested bacteria. The highest zone of inhibition was observed against Escherichia coli MTCC 739 (17.32 ± 0.6 mm), followed by Staphylococcus aureus MTCC 96 (16.4 ± 1.1 mm) and Bacillus cereus MTCC 430 (12.4 ± 0.9 mm). No inhibition was detected against Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterococcus faecalis, Micrococcus luteus, or MDR E. coli. The methanolic extract showed a minimum inhibitory concentration of 2560 µg/mL against E. coli. In the DPPH assay, the methanolic extract exhibited concentration-dependent radical-scavenging activity, increasing from 4.54 ± 0.8% at 10 µg/mL to 60.32 ± 1.4% at 2560 µg/mL. The ethyl acetate and hexane extracts showed substantially lower antioxidant activity. These findings indicate that Antarctic Pseudogymnoascus sp. represents a promising source for further investigation of fungal metabolites with antibacterial and antioxidant properties.