Production Optimization and Potential Bioactivities of Biosurfactant from PET Surface-Dwelling Oligotrophic Bacillus sp. EIKU23.

The growing demand for efficient biosurfactants in various industrial sectors has driven the search for sustainable alternatives, enhanced production methods, and low-cost substrates. This study aimed to optimize the production, characterize, and assess the bioactivities of biosurfactants produced by an oligotrophic PET plastic-associated Bacillus sp. EIKU23. The bacterium yielded the highest amount of biosurfactant after 6 days of incubation in Luria broth medium (pH 7.0) at 30 °C without any additives. FTIR and NMR analyses confirmed the lipopeptide nature of the biosurfactant, which exhibited a negative charge. The biosurfactant remained stable at 4 °C-80 °C and pH 7.0-8.0 for at least 7 days. It exhibited antioxidant properties comparable to the ascorbic acid standard, with efficacy ranging from 23.61% to 89.96% in different antioxidant assays. It showed antibacterial activity against both Gram-positive and Gram-negative potential pathogens. The biosurfactant induced substantial DNA leakage at a concentration of 10 mg/mL and eradicated approximately 48.4% of pre-formed Staphylococcus aureus biofilm and showed anti-attachment behaviour to a polystyrene surface. Additionally, the biosurfactant precipitated up to 98.7% uranium from an aqueous solution, demonstrating its potential for bioremediation. These findings suggest that the biosurfactant produced by Bacillus sp. EIKU23 is multifunctional with promising applications in bioremediation, antibacterial activity, antibiofilm formation, and antioxidant defense, offering a novel solution for sustainable industrial practices and plastic waste management.