Isolation and Functional Characterization of a Lipopeptide Biosurfactant From a Novel <i>Novosphingobium lentum</i> TR17 Strain With Potential for Industrial and Bioremediation Applications

Biosurfactant-producing bacteria were isolated from used lubricating oil (ULO)-contaminated soil in Phuket and Trang, southern Thailand. Screening for biosurfactant production was conducted using surface tension reduction and emulsification activity. The highest surface tension reduction was observed in a strain identified as Novosphingobium lentum TR17 using 16S rRNA gene analysis. The selected strain demonstrated optimal biosurfactant production using glucose and commercial monosodium glutamate as carbon and nitrogen sources, respectively. After 60 h of cultivation, the biosurfactant yield reached 5.30 g/L, with a surface tension reduction from 72 to 25 mN/m. The biosurfactant, recovered using a chloroform:methanol solvent system, exhibited thermal and pH stability, a low critical micelle concentration (9 mg/L), and high emulsification activity. Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and mass spectrometry confirmed its lipopeptide nature. Additionally, the crude biosurfactant demonstrated antibacterial properties and enhanced the solubility of polyaromatic hydrocarbons (PAHs), suggesting its potential for bioremediation and industrial applications.