The experimental studies of the amino acid composition of the skimmed cow milk fermented with kefir corns, natural kurunga symbiotic starter and bacterial concentrate of the microbial consortium (BСMC) have been carried out. The bacterial concentrate of the microbial consortium is intended for the preparation of a fermented milk beverage of mixed fermentation – kurunga. The microbial consortium obtained by autoselection of population of kefir corn starter and thermophilic lactobacteriums Lactobacillus bulgaricus and Lactobacillus acidophilum has been used to prepare BCMC. The amino acid analysis of the samples has been carried out by IC method with postcolumn derivatization of amino acids ninhydrin in the acid hydrolyzate of the sample on INGOSAAA-400 amino acid analyzer. The most of essential amino acids has been found in kefir – 434 mg/g of protein. In the samples prepared with natural starter and bacterial concentrate, the total amount of essential amino acids has been 401.84 and 403.8 mg/g of protein, respectively. Exogenous amino acids are essential for the growth of lactics and yeast. The difference in the total amount of the essential amino acids in the samples, probably, caused by the proteolytic activity of the starters and the growth requirements of the microorganisms. The assessment of the bioavailability has been carried out by the method of I.A. Rogov and N.N. Lipatov according to the coefficients of differences between the amino-acid score (CDAS) and bioavailability. The amino-acid scoring studies have shown that the protein in the studied samples is characterized by a complete composition. According to bioavailability, the kurunga samples exceeded kefir by 0.55-0.75%. The obtained results indicate that according to the biochemical activity, the bacterial concentrate of the microbial consortium is practically identical to kurunga prepared with natural starter. It makes possible to obtain a product bioavailably identical to a traditional beverage.

1. Zandanova T.N. Selection of a nutrient medium for obtaining a bacterial concentrate of a microbial consortium. Vestnik VSGUTU. 2018. no. 2. pp. 67–72. (in Russian).

2. Nadtochy L.A., Arsenyeva T.P. Bukachakova L.Ch. Vitamin composition and biological value of the Altai fermented milk drink chegen. Scientific journal NRU ITMO. Series "Processes and Apparatus for Food Production". 2014. no. 4. pp. 1–6. (in Russian).

3. Nechaev A.P., Traubenberg S.E., Kochetkova A.A. etc. Food chemistry; 5th ed., Revised and added. Saint Petersburg, GIORD, 2012. 672 p. (in Russian).

4. Lisin P.A., Kanushina Yu.A. Amino acid composition of the curd product. Dairy industry. 2011. no. 11. pp. 64-65. (in Russian).

5. Stoyanova L.G., Ustyugova E.A., Netrusov A.I. Antimicrobial metabolites of lactic acid bacteria: diversity and properties (review). Applied biochemistry and microbiology. 2012. vol. 48. no. 3. pp. 259–275. (in Russian).

6. Krumlikov V.Yu., Isambetova L.V. Investigation of antibiotic resistance, cultural and morphological properties of microorganisms isolated from national Kazakh drinks. Storage and processing of agricultural raw materials. 2016. no. 9. pp. 31-35. (in Russian).

7. Meister A. Biochemistry of the amino acids. Elsevier, 2012.

8. Wu G. Amino acids: biochemistry and nutrition. CRC Press, 2013.

9. Martinez B., Bottiger T., Schneider T., Rodriguez A. et al. Specific Interaction of the Unmodified Bacteriocin Lactococcin 972 with the Cell Wall Precursor Lipid II. Appl. Environ. Microbiol.2009. vol. 74. pp. 4666–4670.

10. Barrett G. Chemistry and biochemistry of the amino acids. Springer Science & Business Media, 2012.

11. Stadie J., Matthias Gulitz A., Ehrmann Rudi A., Vogel F. Metabolic activity and symbiotic interactions of lactic acid bacteria and yeasts isolated from water kefir. Food Microbiology. 2013. vol. 35. no. 2. pp. 92–98. doi: 10.1016/j.fm.2013.03.009

12. Hati S., Patel N., Sakure A., Mandal S. Influence of whey protein concentrate on the production of antibacterial peptides derived from fermented milk by lactic acid bacteria. International Journal of Peptide Research and Therapeutics. 2018. vol. 24. no. 1. pp. 87-98. doi: 10.1007/s10989-017-9596-2

13. Rama G.R. Kuhn D., Beux S., Maciel M.J. et al. Potential applications of dairy whey for the production of lactic acid bacteria cultures. International Dairy Journal. 2019. vol. 98. pp. 25-37. doi: 10.1016/j.idairyj.2019.06.012

14. Mohammadi R., Sohrabvandi S., Mohammad Mortazavian A. The starter culture characteristics of probiotic microorganisms in fermented milks. Engineering in Life Sciences. 2012. vol. 12. no. 4. pp. 399-409. doi: 10.1002/elsc.201100125

15. Ozcan T., Sahin S., Akpinar?Bayizit A., Yilmaz?Ersan L. Assessment of antioxidant capacity by method comparison and amino acid characterisation in buffalo milk kefir. International Journal of Dairy Technology. 2019. vol. 72. no. 1. pp. 65-73. doi: 10.1111/1471-0307.12560

16. Akabanda F., Owusu-Kwarteng J., Tano-Debrah K., Parkouda C. et al. The use of lactic acid bacteria starter culture in the production of Nunu, a spontaneously fermented milk product in Ghana. International journal of food science. 2014. vol. 2014. doi: 10.1155/2014/721067

17. Ili?i? M.D., Milanovi? S.D., Cari? M.?., Vuki? V.R. et al. The effect of transglutaminase on rheology and texture of fermented milk products. Journal of Texture Studies. 2013. vol. 44. no. 2. pp. 160-168. doi: 10.1111/jtxs.12008

18. Gul O., Mortas M., Atalar I., Dervisoglu M. et al. Manufacture and characterization of kefir made from cow and buffalo milk, using kefir grain and starter culture. Journal of dairy science. 2015. vol. 98. no. 3. pp. 1517-1525. doi: 10.3168/jds.2014-8755

19. Kakimov A., Kakimova Z., Mirasheva G., Bepeyeva A. et al. Amino acid composition of sour-milk drink with encapsulated probiotics. Annual Research & Review in Biology. 2017. pp. 1-7. doi: 10.9734/ARRB/2017/36079

20. Widyastuti Y., Febrisiantosa A.The role of lactic acid bacteria in milk fermentation. Food and Nutrition Sciences. 2014. vol. 2014. doi: 10.4236/fns.2014.54051