Screening, Optimization and Characterization of Exopolysaccharides Produced by Yoghurt-Derived Enterococcus Species and Evaluation of Their Antioxidant and Antibacterial Activities
R. Soundarya
Department of Studies in Microbiology, Davangere University, Shivagangothri, SH-76, Davangere-577007, Karnataka, India.
Devaraja Gayathri *
Department of Studies in Microbiology, Davangere University, Shivagangothri, SH-76, Davangere-577007, Karnataka, India.
*Author to whom correspondence should be addressed.
Abstract
Background: Exopolysaccharides (EPS) produced by lactic acid bacteria have potential technological and biological applications, but their properties vary among isolates.
Aim: The present study aimed to produce and characterize exopolysaccharides (EPS) from Enterococcus species GS 12D and to evaluate their biological and selected technological potential. The primary objective was to select the most productive EPS-producing strain among the Enterococcus isolates and to optimize, characterize and evaluate its biological properties.
Study Design: Screening, growth kinetics and extraction of EPS using MRS medium.
Place and duration of Study: Department of Studies in Microbiology, Davangere University, Davangere 577007, India, from 2023 to 2026.
Methodology: Four lactic acid bacteria from yogurt were screened for their exopolysaccharide production capacity on aniline blue agar plates and the growth kinetics of the Enterococcus sp GS 12D were measured spectrophotometrically using NanoDrop 2000 CC at different incubation times, temperatures and with different carbohydrates using MRS broth. The partially purified EPS was then assessed for biological properties including antibacterial and antioxidant activities.
Results: Among the four strains, Enterococcus sp GS 12D was selected, and the production conditions were optimized: 5% (w/v) sucrose, 45°C and an incubation period of 96 h. The DPPH radical-scavenging activity at 2 mg/mL was 75 ± 0.12 %. The EPS produced by Enterococcus sp. also exhibited antibacterial activity at 0.1 mg/mL against Staphylococcus aureus ATCC 25923, Listeria monocytogenes ATCC 19115, Salmonella typhimurium ATCC 14028, Bacillus subtilis ATCC 6051, Clostridium perfringens ATCC 13124, Proteus vulgaris ATCC 13315, Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922, with the highest antibacterial activity observed against Pseudomonas aeruginosa.
Conclusion: Exopolysaccharides (EPSs) are carbohydrate polymers produced by lactic acid bacteria such as Enterococcus species GS 12D. The results indicated that EPS produced by this bacterium may be a promising functional biopolymer for potential applications in the food and pharmaceutical sectors, subject to further validation.
Keywords: Enterococcus sp. GS 12D, lactic acid bacteria, yogurt-derived isolates, exopolysaccharides, EPS screening, sucrose supplementation, growth kinetics, DPPH radical scavenging, antibacterial activity, antibiotic susceptibility