Exopolysaccharides and conjugated linoleic acid production by selected lactic acid bacteria: physicochemical attributes, antimicrobial activity, and techno-functional properties of exopolysaccharides

Abstract

Lactic acid bacteria (LAB) exopolysaccharides (EPS) are high-value biopolymers that have predominant applications in the food sector due to their thickening, gelling, stabilizing, texturizing, emulsifying, and flocculating properties, while conjugated linoleic acid (CLA) has potential health benefits for humans. This study aims to screen and isolate bacterial strains based on their EPS and CLA production, as well as to characterize the carbohydrate, protein content, water and oil-holding capacity, emulsification, antimicrobial, and hydroxyl radical scavenging activity of EPS. In this study, 50 out of 300 bacterial strains stocked in the laboratory were screened by agar media, and 18 strains were selected based on their EPS production. Afterward, 10 highest EPS producing bacterial strains (Lactobacillus acidophilus, Enterococcus faecium, Lactiplantibacillus plantarum, Streptococcus thermopilus, Lactococcus lactis, Lacticaseibacillus casei, Lactobacillus delbruki spp. bulgaricus, Pediococcus pentosaceus, Lactobacillus paraplantarum, and Lactobacillus delbruki spp. lactis) were evaluated for their CLA production, followed by EPS techno-functional properties. The EPS production varied significantly, from 39.02 mg/L in Lactococcus raffinolactis B425 to 2210.18 mg/L in Lactobacillus acidophilus LDMB01. Considering CLA production, Lactobacillus del. spp. bulgaricus M240 exhibited the highest yield (30.60 µg/mL). In terms of techno-functional properties, Enterococcus faecium D325 showed the highest carbohydrate content (749.89 μg/mL), while Lactobacillus del. spp. bulgaricus M240 exhibited the highest protein content (194.87 μg/mL). Lacticaseibacillus casei LDMB03 demonstrated the highest water-holding (204.28%) and oil-holding (309.59%) capacity. The 10% EPS exhibited the highest antimicrobial activity against the tested pathogenic bacteria, even at relatively low concentrations. Pediococcus pentosaceus B225 showed the strongest emulsification index, whereas the highest hydroxyl radical scavenging activity was recorded in Lactococcus lactis LDMB10 (94.40%). These findings highlight the diverse functional properties of LAB-derived EPS, underscoring their potential in developing functional foods, pharmaceuticals, and cosmetic products.