Biological properties and structural characterization of a novel rhamnolipid like‐biosurfactants produced by Lactobacillus casei subsp. casei TM1B

Biosurfactants are microbial surface‐active compounds with antimicrobial and antioxidant activities that display a range of physiological functions. In this study, a strain isolated from a Cameroonian fermented milk “pendidam” and identified as Lactobacillus casei subsp. casei TM1B was used for biosurfactants production. The biosurfactants produced by L. casei TM1B with molasses as the substrate had a good surface (40.77 mN/m) and emulsifying (84.50%) activities. The scavenging of the ABTS+• radical (IC50 value of 0.60 ± 0.03 mg/mL) by the biosurfactants was found to be higher than that of DPPH• radical (IC50 value of 0.97 ± 0.13 mg/mL). The maximum chelating activity of biosurfactants (82.29%) was observed at 3.5 mg/mL. The biologically active compound of the biosurfactants produced by L. casei TM1B was identified as 2,5‐O‐methylrhamnofuranosyl‐palmitate, a novel rhamnolipid‐like biosurfactant by using chemical, Fourier transform infrared spectroscopy, gas chromatography‐mass spectrometry, and NMR analysis. The biosurfactants were bactericidal against several Gram‐negative and Gram‐positive pathogens (minimum inhibitory concentration values ranged from 3.22 to 12.83 mg/mL), and scanning electron microscope analysis revealed bacterial cell walls and membranes as main targets. Biological properties of the biosurfactant from L. casei