Abstract: Antibiotic resistance and biofilm-associated infections are major global health concerns, requiring sustainable antimicrobial alternatives. This study aimed to evaluate the antibacterial, antifungal, and antibiofilm potential of biosurfactants produced by Bacillus strains (H1, H2, and H5) isolated from the fat of Catla catla, a freshwater fish from the Sutlej River, Pakistan. The biosurfactants were extracted, purified, and characterized using Fourier transform infrared spectroscopy, high-performance liquid chromatography, and mass spectrometry. Quantitative analysis revealed that strain H5 produced the highest levels of surfactin (107.5 ± 0.3 mg L-1) and iturin A (60.5 ± 0.5 mg L-1). The biosurfactants exhibited strong antibacterial activity, producing inhibition zones of up to 28.3 ± 0.3 mm against Bacillus licheniformis and 24.3 ± 0.3 mm against Escherichia coli. Minimum inhibitory and bactericidal concentrations against Staphylococcus aureus were 6.6 ± 0.6 µg mL-1 and 11.8 ± 0.4 µg mL-1, respectively. Antifungal tests showed up to 34.6 ± 0.3 mm inhibition zones against Fusarium moniliforme. Antibiofilm assays demonstrated that the extracellular biosurfactant from strain H2 achieved the highest inhibition (82.7 ± 0.3 %) at 50 µg mL-1. Phylogenetic analysis confirmed the isolates as Bacillus subtilis (PV789583), Bacillus thuringiensis (PV789584), and Bacillus cereus (PV789585). These findings indicate that biosurfactants derived from Catla catla fat as a substrate represent a cost-effective and eco-friendly source of potent antimicrobial and antibiofilm compounds with promising biotechnological and therapeutic applications.
Jurrat et al. (Thu,) studied this question.