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 likebiosurfactant by using chemical, FTIR, gas chromatography-mass spectrometry, and NMR
analysis. The biosurfactants were bactericidal against several Gram-negative and Grampositive pathogens (MIC values ranged from 3.22 to 12.83 mg/mL), and SEM analysis
revealed bacterial cell walls and membranes as main targets.