Improvement of water in oil emulsion physicochemical stability using biosurfactants from indigenous Lactobacilli isolated from Pendidam

Abstract

Lactic acid bacteria are promising sources of biosurfactants with potential applications as natural emulsifiers in cosmetic formulations. This study aimed to isolate biosurfactant-producing Lactobacillus strains from Pendidam and evaluate the emulsifying performance of their crude biosurfactants in water-in-oil (W/O) beauty milk formulations. From six samples of Pendidam, twelve presumptive Lactobacillus isolates were characterized using morphological, physiological, and biochemical tests. Biosurfactant production was screened by hydrocarbon-overlaid agar and oil spreading assays, after which selected crude biosurfactants were incorporated into W/O beauty milk formulations. Emulsion particle size distribution and viscosity were subsequently determined. All isolates were Gram positive, catalase- and oxidase-negative, non-motile, heterofermentative rods typical of the genus Lactobacillus. Five isolates (S1, S2, S3, S4, and S5), exhibited both emulsifying and surface activities. Oil spreading diameters ranged from 6 to 28 mm, confirming biosurfactant production. Formulations containing biosurfactants produced droplets ranging from 4.94 to 7.61 μm, compared with 16.34 μm for the negative control. The smallest droplet size (4.94 μm) was obtained with the isolated S5, while emulsion viscosity varied significantly from 967 to 1715 mPa.s among biosurfactant-based formulations, compared with 1998 mPa.s for the positive control. These findings demonstrate that biosurfactant produced by Pendidam-derived Lactobacillus, particularly isolate S5, possess promising emulsifying properties and represent sustainable alternatives to synthetic emulsifiers for cosmetic applications.