Antibacterial Potential of Marine Aspergillus Austroafricanus: Metabolite Optimization, Gc–ms Characterization, in Vitro Activity and in Silico Mechanistic Evaluation

This study aimed to isolate fungi from marine stones collected from the Oron River near the Atlantic Ocean, identify the isolates, and evaluate their antibacterial potentials. Marine stone samples were brushed into 10 mL phosphate-buffered saline, serially diluted, and cultured on Czapek–Dox agar for fungal isolation. Pure isolates were screened for antibacterial activity and identified using molecular techniques. Metabolite production was optimized under varying cultural conditions. Selected fungi were cultured in Czapek–Dox broth, and crude extracts were evaluated using the agar well diffusion method. Active extracts were fractionated, and the most potent fractions were analyzed by GC–MS. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using standard methods. Metabolite production was optimized, and the mechanisms of action of bioactive compounds were investigated using molecular docking. Molecular docking and ADMET profiling were performed to assess target interactions and pharmacokinetic properties. Aspergillus austroafricanus was isolated and exhibited broad-spectrum antibacterial activity, with mean inhibition zones of 25.6 mm against Staphylococcus aureus, 20.8 mm against Escherichia coli, and 15 mm against Pseudomonas spp. and Bacillus cereus. GC–MS revealed bioactive compounds with superior activity compared to standard antibiotics. Optimal metabolite production occurred at pH 8, temperature of 25 °C, using lactose and potassium nitrate supplements. Docking studies showed strong binding to bacterial DNA gyrase (up to −7.6 kcal/mol), while ADMET analysis predicted high oral absorption. Marine-derived fungal metabolites demonstrated potent antibacterial activity and favourable pharmacokinetic profiles, highlighting their potential as novel agents against drug-resistant bacteria.