## 3 Results and Discussion
### Population of Bifidobacterium sp. The number of BB-12 monoculture cells was, on average, 9.0 log CFU/mL \(\pm\) 0.2 immediately prior to use. The number of _Lactobacillus acidophilus_ was, on average, 7.1 CFU/mL \(\pm\) 0.3, while the number of _Bifidobacterium_ was 6.5 CFU/mL \(\pm\) 0.3 when using the original commercial kumis (OK samples) at the time of inoculation of the mare's milk. A high population of bifidobacteria was observed (Table 4) both in the B samples of the fermented mare's milk and in the C samples of unfermented mare's milk containing the BB-12 monoculture. The recorded changes in the bifidobacteria populations were statistically significant (\(p<0.05\)). The observed reduction in the number of bifidobacteria in the analyzed B samples was statistically significant from the 7 th day of the analysis and \begin{table}
\begin{tabular}{c c c c c c} \hline
**Storage Day** & **A Samples** & **B Samples** & **C Samples** & **K Samples** & **OK Samples** \\ \hline
1 & 4.05 \(\pm\) 0.010 a\({}^{*}\) & 5.92 \(\pm\) 0.047 a & 6.80 \(\pm\) 0.021 a & 3.88 \(\pm\) 0.006 a & 3.17 \(\pm\) 0.032 a \\
7 & 3.89 \(\pm\) 0.006 b & 5.75 \(\pm\) 0.053 a & 6.25 \(\pm\) 0.042 b & 3.89 \(\pm\) 0.035 a & 3.25 \(\pm\) 0.064 a \\
14 & 3.95 \(\pm\) 0.015 c & 4.75 \(\pm\) 0.118 b & 5.62 \(\pm\) 0.031 c & 3.79 \(\pm\) 0.010 b & 3.19 \(\pm\) 0.015 a \\
21 & 3.97 \(\pm\) 0.012 c & 4.23 \(\pm\) 0.087 c & 4.99 \(\pm\) 0.023 d & 3.77 \(\pm\) 0.040 b & 3.17 \(\pm\) 0.026 a \\ \hline \end{tabular} \({}^{*}\)The same letter in the same column means that there is no statistically significant difference for \(p<0.05\).  
\end{table} 
Table 3: pH values of mare’s milk samples during storage for 21 days at 5 \(\pm\) 1 \({}^{\circ}\)C (means and standard deviations). from the 14 th day of cold storage in the C samples. These samples differed in that the first one was fermented and the second was not. This was reflected in the values of active acidity measured in the B and C samples (Table 3). A significantly smaller population of _Bifidobacterium_ sp. was found in the K and OK samples (Table 4). A reduced population of bifidobacteria was observed during storage at 5 \({}^{\circ}\)C. For the K samples, the reduction in the bifidobacteria population was statistically significant from the 14 th day of cold storage and was not statistically significant for the OK sample (\(p\) < 0.05). The pH of these samples was very low, possibly contributing to the reduction in bifidobacteria (Table 3). The difference in the population of bifidobacteria between the K and the OK samples is questionable. For reminiscence, the K samples contained mare's milk fermented with the 40% original commercial kumis in relation to the amount of mare's milk used and with the addition of 7% of LA-5 monoculture, while the OK samples contained the original commercial kumis. The high mortality of the BB-12 bacteria in the original kumis (OK samples) is due to their highly documented sensitivity to low pH and may be caused by the production of hydrogen peroxide by some lactobacillus strains present in the kumis [13]. We can speculate that the extremely low pH in the OK samples is the result of the total metabolic activity of different lactobacilli strains (not only LA-5) present in the original kumis. Different lactobacilli strains present in the original kumis have metabolic activity characterized by the production of metabolic products resulting in a very low pH of the environment, which contributes to the low survival of the BB-12 strain in the OK samples. In contrast to the OK samples, the presence of an additional LA-5 culture in the K samples may cause competition for the substrate (i.e., an antagonist relationship) and result in inhibition of the metabolic activity of other lactobacilli strains responsible for the acidification of the environment. It may result in a higher pH of the K samples than the OK samples and, thus, higher survival of the BB-12 bacteria in the K samples compared to the OK samples (Table 3).