Statistical optimization of production and characterization of biosurfactant produced by Lactobacillus plantarum JBC5 strain in a ghee (clarified butter) medium: Assessment of its antimicrobial activity and stain removal property

Abstract

This investigation focused on optimizing and characterizing a biosurfactant derived from Lactobacillus plantarum JBC5, which was isolated from local curd. Ghee, a clarified butter that has not previously been explored as a substrate, was used for biosurfactant production. The Plackett-Burman factorial design identified significant parameters affecting bacterial growth and biosurfactant production, whereas response surface methodology (RSM) predicted optimal production at 3.2 g/L ± 0.08 g/L, which was experimentally validated at 3.1 ± 0.09 g/L.The column-purified biosurfactant demonstrated a critical micelle concentration of 100 mg/L, reducing water's surface tension to 34.0 ± 0.03 mN/m. The emulsification index (E₂₄) of biosurfactants with edible oils was 59.8 %, making them a viable alternative to synthetic surfactants. Lipopeptide composition of biosurfactant was confirmed using nuclear magnetic resonance (NMR) and liquid chromatography-mas spectrometry analyses (LC-MS). Thermal analyses showed excellent heat stability as the crystallization and melting points were determined at 95.68°C and 276.72°C, respectively, suggesting its suitability for high-temperature industrial use. Combined with commercial facewash, the biosurfactant improved wash performance, as evidenced by increased post-wash solution absorbance. Antibacterial assay of biosurfactant showed bacteriostatic action against Staphylococcus aureus, with 61.3 % growth inhibition at 500 μg/mL. These findings position the biosurfactant as a promising candidate for cosmetic and industrial applications.