Probiotic-Derived Exopolysaccharide as a Natural Stabilizer for Limonene Emulsions: A Novel Approach to Enhancing Stability and Bioactive Properties

Abstract

Lactobacillus-derived (LAB) exopolysaccharide (EPS) was used as an emulsifier to encapsulate Limonene enantiomers consisting of S-limonene (SL) and D-limonene (DL). EPS and emulsions were analyzed for physiochemical and rheological behavior, followed by emulsifying stability and antimicrobial activity against food-borne pathogens. EPS was extracted and yielded 1.1 g/L amount with an optimized supplementation of 5% carbon source at pH 6.1 and characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA), along with physiochemical properties. At 2% EPS in 60/40 O/W emulsion, a desired mean particle size and polydispersity index (PDI) were acquired by comparing different O/W ratios. Optimized emulsions showed higher stability under different physiological parameters: temperatures (− 20 to 60 °C), pH (2–9), and salinity. In FTIR analysis, emulsions showed OH and C = O stretching acquired from EPS and the presence of cyclohexane-1-ene group from encapsulated limonene. Notably, our study is among the first to demonstrate LAB-derived EPS as a natural and effective emulsifier for stabilizing limonene, providing improved stability and antimicrobial efficacy against Escherichia coli and Listeria monocytogenes compared to free oils. These findings illustrate that LAB-derived EPS is a promising natural emulsifier for encapsulating volatiles, with significant applications in food safety.