## 3 Results and Discussion
### Population of Lactobacillus sp. and Streptococcus sp. The number of thermophilic _Lactobacillus_ sp. and _Streptococcus_ sp. (Table 5) was tested in the K and OK samples. The observed change was statistically significant but only on the last day of the analysis of the OK samples. For comparison, the number of _Streptococcus_ sp. from the beginning was less than the tested lactobacilli and was significantly reduced only in the OK samples (\(p<0.05\)). The observed change was statistically significant from the 14 th day of sample storage (Table 5). Among the microflora of the kumis, the yogurt bacteria _Lactobacillus delbrueckii_ subsp. _bulgarcius_ and _Streptococcus thermophilus_[64] are also observed. Therefore, a microbiological analysis of the original commercial kumis (OK samples) was performed for the presence and survival of thermophilic _Lactobacillus_ sp. and _Streptococcus_ sp. Our research has shown that _Lactobacillus_ sp. is more effective in the environment of fermented mare's milk than _Streptococcus_ sp. Both lactobacilli and streptococci did not show statistically significant reductions in their populations during the refrigeration storage of K samples (\(p<0.05\); Table 5). The survival of _Lactobacillus_ sp. is confirmed in studies by [PERSON] et al. [15], who observed good survival for lactobacilli isolated from kumis during 3 weeks of storage at 4 \({}^{\circ}\)C. In general, the literature data reported good survival for _Lactobacillus_ sp. under refrigerated conditions [53; 65]. [PERSON] et al. [54] demonstrated that the number of lactobacilli cells did not change significantly during cold storage in yogurts obtained from cow's milk under laboratory conditions. Our experiments have shown that _Streptococcus thermophilus_ bacteria in fermented mare's milk are more susceptible to cold storage than _Lactobacillus_ sp. The survival rates of _Streptococcus thermophilus_ are consistent with previous research [66; 67; 13] obtained on other strains of this species. Recent studies have reinforced the understanding of _Streptococcus thermophilus_ survival in fermented milk products during storage. A 2020 study found that fermented milks co-cultured with _Streptococcus_ thermophilus_ maintained higher viable cell counts and better sensory qualities over a 21-day storage period at 4 \({}^{\circ}\)C compared to those using pure strains. The co-cultures with _Bifidobacterium animalis_ and _Lactiplantiobacillus plantarum_ also exhibited enhanced proteolytic and lipolytic capacities, which contributed to their favorable qualities [67]. These findings highlight the beneficial interactions between _Streptococcus thermophilus_ and other lactic acid bacteria, promoting a more stable and bioactive product during storage. This indicates changes in the reciprocal proportions of the lactic acid bacteria during the storage of fermented milk beverages. According to the FAO/WHO Standard [68], for the kumis microflora, the number of lactobacilli of the species _Lactobacillus delbrueckii_ subsp. _bulgarcius_ should be 10\({}^{7}\) CFU/g and a minimum of 10\({}^{4}\) CFU/g for yeast _Kluyveromyces marxianus_. This is the so-called \"technical microflora\", whose population should be maintained at the indicated level