Dependence of the amino acid profile and antioxidant potential of fermented milk products on the enzymatic activity of lactic acid microorganisms

Introduction: The enzymatic activity of lactic acid microorganisms (LAM) plays a decisive role in shaping the amino acid composition and functional properties of fermented dairy products. However, direct relationships between the enzymatic profile of individual strains and the antioxidant potential of the product remain insufficiently studied.

Purpose: To determine the effect of Lactobacillus acidophilus, Lactobacillus bulgaricus, and Streptococcus thermophilus strains on the amino acid profile and antioxidant properties of fermented dairy products.

Materials and methods: The study involved 12 LAM strains from the collection of VNIMI. Enzymatic activity was assessed using the API ZYM test system; amino acid composition was determined by capillary electrophoresis; glutathione content was measured by titrimetric analysis; antioxidant activity was evaluated amperometrically.

Results: L. acidophilus strains demonstrated the highest proteolytic activity, which was associated with an increased content of sulfur-containing amino acids (cystine, methionine) and higher antioxidant activity. L. bulgaricus exhibited moderate values, whereas S. thermophilus showed low antioxidant activity but ensured significant accumulation of glutamic acid, a precursor of glutathione.

Conclusion: A direct relationship between the amino acid profile and antioxidant potential of fermented dairy products and the enzymatic activity of LAM strains was established. The findings confirm the potential of specific strains for targeted enhancement of the functional properties of fermented dairy products and for the selection of starter cultures with predictable biotechnological potential.

1. Donskaya, GA & Krekker, LG (2022). Influence of redox processes on the antioxidant activity of the symbiotic starter biomass. Food systems, 5(4), 337-343. (In Russ) https://doi.org/10.21323/2618-9771-2022-5-4-337-343 (In Russ).

2. Donskaya, GA, Bychkova, TS & Yurova, EA. (2024). Investigation of the radioprotective potential of oilseed flour. Polzunovsky bulletin, (4), 86-92. (In Russ) https://doi.org/10.25712/ASTU.2072-8921.2024.04.013

3. Zobkova, ZS. (2020). Dependence of the relative biological value of fermented milk drinks on the type of starter microorganisms. Dairy industry, (8), 36-37. (In Russ) https://doi.org/10.31515/1019-8946-2020-08-36-37

4. Kanochkina, MS et al. (2023). Features of the selection of starter cultures in the production of functional fermented milk products. Vestnik of MSTU, 26(4), 511–528. (In Russ) https://doi.org/10.21443/1560-9278-2023-26-4-511-528

5. Kolmakova, TS, Belik, SN, Chistyakov, VA, Morgul', EV & Chistyakova, IB. (2014). Characteristics of kefir as a valuable probiotic product and its biological properties. Medical bulletin of the South of Russia, (3), 35-42. (In Russ) https://doi.org/10.21886/2219-8075-2014-3-35-42

6. Rozhkova, IV & Begunova, AV. (2021). Probiotic potencial of Bifidobacterium adolescentis МС-42. Dairy industry, (3), 34-37. (In Russ) https://doi.org/10.31515/1019-8946-2021-03-34-36

7. Yashin, AYa, Yashin, YaI, Chernousova, NI & Pakhomov, VP. (2004). Express electrochemical method for the analysis of antioxidant activity of food products. Beer and Beverages, (6), 32-34. (In Russ).

8. Alexandraki, M., Maisoglou, I., Koureas, M., Kossyva, V., Tzereme, A., Meleti, E., Vrontaki, M., Manouras, V., Dimitriou, L. & Malissiova, E. (2025). Physicochemical Properties and Antioxidant Profile of a Fermented Dairy Beverage Enriched with Coffee By-Products. Beverages, 11(4), 121. https://doi.org/10.3390/beverages11040121_

9. Ayivi, R. D. & Ibrahim, S. A. (2022) Lactiс acid bacteria: An essential probiotic and starter culture for the production of yoghurt. International Journal of Food Science & Technology, 57(11), 7008-7025. https://doi.org/10.1111/ijfs.16076

10. Balthazar, C.F., Teixeira, S., Bertolo, M-R.V., Ranadheera, C.S., Raices, R-S.L., Russo, P., Spano, G., Bogusz, S.J., Cruz, A.G. & Anderson S.A. (2024). Functional benefits of probiotic fermented dairy drink elaborated with sheep milk processed by ohmic heating. Food Bioscience, 59, 103781. https://doi.org/10.1016/j.fbio.2024.103781

11. Dan, T., Hu, H., Tian, J. & He, B. (2023) Influence of different ratios of Lactobacillus delbrueckii subsp. Bulgaricus and Streptococcus thermophilus on fermentation characteristics of yogurt. Molecules, 28(5), Article number 2123. https://doi.org/10.3390/molecules28052123

12. de Melo Pereira, G. V., de Carvalho Neto, D. P., Junqueira, A. C. D. O. & Karp, S. G. (2020) A review of selection criteria for starter culture development in the food fermentation industry. Food Reviews International, 36(2), 135-167. https://doi.org/10.1080/87559129.2019.1630636

13. Feng, T. & Wang J. (2020) Oxidative stress tolerance and antioxidant capacity of lactic acid bacteria as probiotic: a systematic re-v view. Gut Microbes, 12(1), https://doi.org/10.1080/19490976.2020.1801944

14. Gilmour, S.R., Holroyd, S.E., Fuad, M.D., Elgar, D. & Fanning, A.C. (2024). Amino Acid Composition of Dried Bovine Dairy Powders from a Range of Product Streams. Food, 13(23), 3901. https://doi.org/10.3390/foods13233901

15. Gu, Y., Li, Xi., Xiao, R. & Dudu, O. E. (2020) Impact of Lactobacillus paracasei IMC502 in coculture with traditional starters on volatile and non-volatile metabolite profiles in yogurt. Process Biochemistry, (99), 61-69. https://doi.org/10.1016/j.procbio.2020.07.003

16. Holzapfel, W.H. (2002) Appropriate Starter Culture Technologies for Small-Scale Fermentation in Developing Countries. International Journal of Food Microbiology, 75, 197-212. https://doi.org/10.1016/S0168-1605(01)00707-3

17. Lepecka, A., Szymański, P. & Okoń, A. (2025). Isolation, identification, and evaluation of the antioxidant properties of lactic acid bacteria strains isolated from meat environment. PloS One, 20(7), e0327225. https://doi.org/10.1371/journal.pone.0327225

18. Loghman, S., Moayedi, A., Mahmoudi, M., Khomeiri, M., Gómez-Mascaraque, L.G. & Garavand, F. (2022). Single and co-cultures of proteolytic lactic acid bacteria in the manufacture of fermented milk with high ACE inhibitory and antioxidant activities. Fermentation, 8(9), 448. https://doi.org/10.3390/fermentation8090448

19. Mataczewska, J. & Kaczorek-Lukowska, E. (2021) Nisin-A lantibiotic with immunomodulatory properties: A review. Peptides. (137), Article 170479. https://doi.org/10.1016/j.peptides.2020.170479

20. Park, J., Hirano, J-I, Thangavel, V., Riebel, B. & Bommarius, A. (2011). NAD(P)H oxidase V from Lactobacillus plantarum (NoxV) displays enhanced operational stability even in absence of reducing agents. Journal of Molecular Catalysis B: Enzymatic, (71), 159-165. https://doi.org/10.1016/j.molcatb.2011.04.013

21. Poluektova, E., Yunes, R. & Danilenko, V. (2021) The putative antidepressant mechanisms of probiotic bacteria: relevant genes and proteins. Nutrients, 13(5), 1591. https://doi.org/10.3390/nu13051591

22. Stasiewicz, Anna & Skrzydlewska, Elzbieta. (2020). Thioredoxin-dependent system. Application of inhibitors. Journal of Enzyme Inhibition and Medicinal Chemistry, (36). 362-371. https://doi.org/10.1080/14756366.2020.1867121

23. Stobiecka, M., Król, J. & Brodziak, A. (2022). Antioxidant Activity of Milk and Dairy Products. Animals,12(3), 245. https://doi.org/10.3390/ani12030245

24. Ulmer, A., Erdemann, F., Mueller, S., Loesch, M., Wildt, S., Jensen, M.L., Gaspar, P., Zeidan, A.A. & Takors, R. (2022). Differential amino acid uptake and depletion in mono-cultures and co-cultures of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus in a novel semi-synthetic medium. Microorganisms, 10(9), 1771. https://doi.org/10.3390/microorganisms10091771

25. Vamanu, E. & Gatea, F. (2020) Correlations between microbiota bioactivity and bioavailability of functional compounds: A mini-review. Biomedicines, 8(2), Article 39. https://doi.org/10.3390/biomedicines8020039.17:28

26. Vasudha, M, Prashantkumar, CS, Bellurkar, M, Kaveeshwar, V & Gayathri, D. (2023). Probiotic potential of β-galactosidase-producing lactic acid bacteria from fermented milk and their molecular characterization. Biomedical Reports, 18(3), 23. https://doi.org/10.3892/br.2023.1605.

27. Weimer, A., Kohlstedt, M., Volke, D. C., Nikel, P. I., & Wittmann, C. (2020). Industrial biotechnology of Pseudomonas putida: advances and prospects. Applied Microbiology and Biotechnology, 104(18), 7745–7766. https://doi.org/10.1007/s00253-020-10811-9

28. Wijesekara, A., Weerasingha, V., Jayarathna, S., Vidanarachchi, J.K. & Priyashantha, H. (2025). Microbial strains in fermented dairy: Unlocking biofunctional properties and health benefits. International Journal of Food Science, 2025, 6672700. https://doi.org/10.1155/ijfo/6672700

29. Zheng, J., Wittouck, S., Salvetti, E., Franz, C.M.A.P., Harris, H.M.B., Mattarelli, P., O' Toole, P.W., Pot, B., Vandamme, P., Walter, J., Watanabe, K., Wuyts, S., Felis, G.E., Gänzle, M.G. & Lebeer S. (2020) A taxonomic note on the genus Lactobacillus: Description of 23 novel genera, emended description of the genus Lactobacillus Beijerinck 1901, and union of Lactobacillaceae and Leuconostocaceae. The International Journal of Systematic and Evolutionary Microbiology, 70(4), 2782-2858. https://doi.org/10.1099/ijsem.0.004107