Low-cost biosurfactant production by Achromobacter xylosoxidans PX106473 from waste frying oil: partial characterization and antimicrobial mechanism via molecular docking

BACKGROUND: Interest in microbial biosurfactants has increased due to the rising demand for environmentally friendly and sustainable surfactants. Waste frying oil provides a renewable and low-cost feedstock for their production. This study aimed to isolate, characterize, and evaluate the antibacterial mechanism of a biosurfactant synthesized by Achromobacter xylosoxidans PX106473 using waste frying oil as an economical carbon source. RESULTS: Achromobacter xylosoxidans PX106473 produced a biosurfactant with significant activity, including an emulsification index (E24%) of 66.7% against kerosene and substantial oil displacement and hemolytic activities. According to the results of thin-layer chromatography (TLC), the produced biosurfactant contained lipids and amino acids. Fourier transform infrared spectroscopy (FT-IR) results revealed the presence of an N-H group, aliphatic hydrocarbons, and amide peaks, which suggest a lipid-peptide linkage, providing further evidence for its putative lipopeptide nature. Hexadecanoic acid, with an area percentage of 76.44, was the dominant component of the lipopeptide based on gas chromatography-mass spectrometry (GC-MS) results. The produced biosurfactant demonstrated good inhibitory activity against E. coli and S. aureus. These biological findings were further supported by in silico assays; molecular docking studies showed that hexadecanoic acid binds stably to key bacterial proteins from E. coli (DNA gyrase B, -6.4 kcal/mol) and S. aureus (PBP2a, -3.9 kcal/mol), indicating a potential dual-target mechanism. CONCLUSION: Achromobacter xylosoxidans efficiently produced a putative lipopeptide biosurfactant from waste frying oil with strong emulsifying and antibacterial properties, providing an economical and sustainable solution with potential in various environmental and pharmaceutical applications.