Extraction and antioxidant activity assessment of postbiotic exopolysaccharides produced by selected lactic acid bacteria

Résumé

Lactic acid bacteria strains are frequently involved in obtaining fermented products characterized by an enhanced nutritional and sensorial value. Exopolysaccharides are carbohydrate-based macromolecules produced by selected strains of lactic acid bacteria (LAB) as extracellular postbiotic compounds. The extraction techniques used to obtain high exopolysaccharides yields are extremely important factors that directly impact their future utilization and functional properties. In this work, the exopolysaccharides produced by two LAB strains, belonging to genus Lactobacillus and Leuconostoc, were extracted from the fermentation medium following two different protocols that employed trichloroacetic acid (TCA) and/ or absolute ethanol. The highest exopolysaccharide extraction yield (956.60 mg/L) was determined after proteins’ precipitation with TCA from the fermented medium by Leuconostoc spp. MIUG BL40 strain. The crude exopolysaccharides biosynthesized by the strain mentioned above had the highest ABTS radical scavenging activity (28.53%) at 10 mg/mL. Therefore, DPPH radical scavenging rates ranging between 2.99-3.30% were calculated for the studied exopolysaccharides. Overall, the results reported in this work offer promising research perspectives that will be further investigated.