*2.3. Cultivation Conditions for B. velezensis BZR 86 and B. velezensis BZR 277 Strains*

In our studies, five parameters were identified that affect the growth of strains in the process of periodic cultivation: cultivation temperature, the acidity of the medium, sources of carbon and nitrogen nutrition, and cultivation time. During the study, we found that some parameters, such as temperature and acidity of the environment, have a significant effect on cell growth. When the incubation temperature changed from 20 to 35 ◦C, and the acidity of the medium from 3 to 10, there was significant variation in the titer (Table 2).


**Table 2.** The number of colony-forming units in liquid cultures is based on strains *B. velezensis* BZR 86 and *B. velezensis* BZR 277, depending on the cultivation conditions.

<sup>1</sup> The error corresponds to the standard deviation of three independent analyses. <sup>2</sup> Between the options marked with the same letters, when comparing within the columns there are no statistically significant differences according to the Duncan criterion at a 95% probability level-% increase to control. Each optimal parameter is determined while keeping the other parameters unchanged.

A high spore or cell titer for the *B. velezensis* BZR 86 strain was noted at a temperature of 35 ◦C and for the *B. velezensis* BZR 277 strain at a temperature of 30 ◦C. The optimal pH for both strains was three. Different nutrient sources had a more significant effect on cell growth. Thus, molasses had appeared to be the optimal carbon source for both strains. The highest titer was recorded on a nutrient medium, where peptone was used as a nitrogen source. The maximum cell titer for both strains was noted in the range of 24–36 h of cultivation. When studying the influence of the cultivation time on the dynamics of the growth of the strains, it was noted that the phase of initial growth (the period when the volume of cells increased, but not their number) began after the introduction of the parent culture into the medium and lasted up to 8 h. The phase of the most active growth began 16 h after the introduction of the parent culture and reached its maximum in 24–36 h for both strains. This was followed by a phase of withering away.
