Probiotic potential and antimicrobial efficacy of exopolysaccharide-producing lactic acid bacteria isolated from yoghurt

Abstract

Aim: The study investigates the probiotic potential of exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) isolated from yoghurt samples. It assesses their antimicrobial efficacy against foodborne pathogens, particularly Escherichia coli and Staphylococcus aureus. The objective is to identify LAB strains that can be used as natural preservatives and health-promoting probiotics in functional foods. Methods: Yoghurt samples were collected from household local markets in Rawalpindi, Pakistan. LAB was isolated and identified using selective media, Gram staining, and biochemical tests. EPS production was quantified using the phenol-sulfuric acid method. Probiotic properties, including antimicrobial activity againstE. coli and S. aureus, were evaluated using the disc diffusion method. Strains producing the highest EPS were biochemically characterised using the API Strep system. Results: Of 29 LAB isolates, 12 were identified as significant EPS producers, with Streptococcus thermophilus, Lactococcus lactis, and Limosilactobacillus fermentum demonstrating the highest EPS production (up to 62 µg/mL). These strains exhibited strong antimicrobial activity againstE. coli and S. aureus, with inhibition zones ranging from 2 mm to 32.1 mm. The results confirmed the dual functionality of these strains as both texture enhancers and natural preservatives in food products. Conclusions: The EPS-producing LAB strains, particularly S. thermophilus, L. lactis, and L. fermentum, showed significant potential as probiotics and natural preservatives. Their antimicrobial activity and ability to enhance food texture suggest their applicability in the food industry to promote health and improve food safety. Further research should explore their stability in different food matrices for commercial use.

Keywords

Probiotics / exopolysaccharides / lactic acid bacteria / anti-microbial activity / foodborne pathogens

References

[1] Aguilera JM. The food matrix: implications in processing, nutrition and health. Crit Rev Food Sci Nutr. 2019; 59: 3612—29.

[2] Forde CG. Beyond ultra—processed: considering the future role of food processing in human health. Proc Nutr Soc. 2023; 82: 406—18.

[3] Plavec TV, Berlec A. Safety Aspects of Genetically Modified Lactic Acid Bacteria. Microorganisms. 2020; 8: 297.

[4] Mathur H, Beresford TP, Cotter PD. Health Benefits of Lactic Acid Bacteria (LAB) Fermentates. Nutrients. 2020; 12: 1679.

[5] Sauer M, Han NS. Lactic acid bacteria: little helpers for many human tasks. Essays Biochem. 2021; 65: 163-71.

[6] Carraro L, Maifreni M, Bartolomeoli I, Martino ME, Novelli E, Frigo F, et al. Comparison of culture—dependent and —independent methods for bacterial community monitoring during Montasio cheese manufacturing. Res Microbiol. 2011; 162: 231-9.

[7] Maftei NM, Raileanu CR, Balta AA, Ambrose L, Boev M, Marin DB, et al. The Potential Impact of Probiotics on Human Health: An Update on Their Health—Promoting Properties. Microorganisms. 2024; 12: 234.

[8] Sánchez B, Delgado S, Blanco—Míguez A, Lourenço A, Gueimonde M, Margolles A. Probiotics, gut microbiota, and their influence on host health and disease. Mol Nutr Food Res. 2017; 61.

[9] Petrova P, Ivanov I, Tsigoriyna L, Valcheva N, Vasileva E, Parvanova—Mancheva T, et al. Traditional Bulgarian Dairy Products: Ethnic Foods with Health Benefits. Microorganisms. 2021; 9: 480.

[10] Ağagündüz D, Yılmaz B, Şahin TÖ, Güneşliol BE, Ayten Ş, Russo P, et al. Dairy Lactic Acid Bacteria and Their Potential Function in Dietetics: The Food—Gut—Health Axis. Foods. 2021; 10: 3099.

[11] Daba GM, Elnahas MO, Elkhateeb WA. Contributions of exopolysaccharides from lactic acid bacteria as biotechnological tools in food, pharmaceutical, and medical applications. Int J Biol Macromol. 2021; 173: 79-89.

[12] Bibi A, Xiong Y, Rajoka MSR, Mehwish HM, Radicetti E, Umair M, et al. Recent Advances in the Production of Exopolysaccharide (EPS) from Lactobacillus spp. and Its Application in the Food Industry: A Review . Sustainability. 2021; 13: 12429.

[13] Angelin J, Kavitha M. Exopolysaccharides from probiotic bacteria and their health potential. Int J Biol Macromol. 2020; 162: 853-65.

[14] Han X, Yang Z, Jing X, Yu P, Zhang Y, Yi H, et al. Improvement of the Texture of Yogurt by Use of Exopolysaccharide Producing Lactic Acid Bacteria. Biomed Res Int. 2016; 2016: 7945675.

[15] Jurášková D, Ribeiro SC, Silva CCG. Exopolysaccharides Produced by Lactic Acid Bacteria: From Biosynthesis to Health—Promoting Properties. Foods. 2022; 11: 156.

[16] Korcz E, Varga L. Exopolysaccharides from lactic acid bacteria: Techno—functional application in the food industry. Trends Food Sci Technol. 2021; 110: 375-84.

[17] Pourjafar H, Ansari F, Sadeghi A, Samakkhah SA, Jafari SM. Functional and health—promoting properties of probiotics’ exopolysaccharides; isolation, characterization, and applications in the food industry. Crit Rev Food Sci Nutr. 2023; 63: 8194-225.

[18] Chelladhurai K, Ayyash M, Turner MS, Kamal—Eldin A. Lactobacillus helveticus: Health effects, current applications, and future trends in dairy fermentation . Trends Food Sci Technol. 2023; 136: 159-68.

[19] Hatti—Kaul R, Chen L, Dishisha T, El Enshasy H. Lactic acid bacteria: from starter cultures to producers of chemicals. FEMS Microbiol Lett. 2018; 265: fny213.

[20] Smith AC, Hussey MA. Gram Stain Protocols[Internet]. American Society for Microbiology; c2016 [cited 2024 Jul 19]. Available from: https://asm.org/getattachment/5c95a063—326b—4b2f—98ce—001de9a5ece3/gram—stain—protocol—2886.pdf

[21] Collins CH, Lyne PM, Grange JM. Collins and Lyne’s Microbiological Methods. Butterworths; 1989.

[22] DuBois M, Gilles KA, Hamilton JK, Rebers PT, Smith F. Colorimetric method for determination of sugars and related substances. Anal Chem. 1956; 28: 350-6.

[23] Tarifa MC, Agustín MDR, Brugnoni LI. Biological control of foodborne pathogens by lactic acid bacteria: A focus on juice processing industries. Rev Argent Microbiol. 2023; 55: 378-86.

[24] Davenport EK, Call DR, Beyenal H. Differential protection from tobramycin by extracellular polymeric substances from Acinetobacter baumannii and Staphylococcus aureus biofilms . Antimicrob Agents Chemother. 2014; 58: 4755-61.

[25] Pang X, Song X, Chen M, Tian S, Lu Z, Sun J, et al. Combating biofilms of foodborne pathogens with bacteriocins by lactic acid bacteria in the food industry. Compr Rev Food Sci Food Saf. 2022; 21: 1657-76.

[26] Prabhurajeshwar C, Chandrakanth RK. Probiotic potential of Lactobacilli with antagonistic activity against pathogenic strains: An in vitro validation for the production of inhibitory substances . Biomed J. 2017; 40: 270-83.

[27] Gänzle MG. Lactic metabolism revisited: metabolism of lactic acid bacteria in food fermentations and food spoilage. Curr Opin Food Sci. 2015; 2: 106-17.