## 3 Results and Discussion
### The Effect of Essential oils on the Viability of Bifidobacterium in In Vitro Conditions
It can be assumed that the antibacterial effect of clove bud essential oils may be related to the content of the active substances present in it. The most active and abundant component in the clove essential oil is eugenol, which has proven antibacterial, as well as antifungal, effects. [PERSON] et al. [46] also confirmed the antimicrobial action of the clove essential oil on the yeast-like fungi _Candida albicans_, the Gram-negative bacteria _E. coli_, and the Gram-positive bacteria _Staphylococcus epidermidis_, as well as the high content of eugenol in this oil. The average size of the growth inhibition zones observed in their study on _C. albicans_, _E. coli_, and _S. epidermidis_ was 11.76 \(\pm\) 0.7, 5.16 \(\pm\) 0.2, and 5.10 \(\pm\) 0.3 mm, respectively. The results presented by [PERSON] et al. [46] are in line with that of our work on the activity of the clove bud essential oil relative to Gram-positive bacteria. [PERSON] et al. [47] performed many studies confirming the strong antimicrobial activity of clove essential oils. [PERSON] et al. [48] and [PERSON] et al. [49] also studied the composition and antimicrobial activity of clove essential oils. Similar to our study, the results of [PERSON] et al. [48] showed that eugenol is the main component of the clove essential oil, and caryophyllene, eugenol acetate, and \(\alpha\)-humulene are also abundant. The cited researchers also showed the inhibitory effects of oil on Gram-positive and Gram-negative bacteria, as well as yeast-like fungi, with the smallest growth inhibition zone observed for _Enterobacter cloace_ and _E. coli_ bacteria (10 mm) and the largest for the yeast-like fungi _C. albicans_ (35 mm). Gram-positive bacteria (_S. aureus_) were shown to be more sensitive to clove essential oils (the largest growth inhibition zone was 23 mm), where the largest inhibition zones were recorded for samples treated with the largest concentration of the clove essential oil. Based on the strength of the inhibitory effects on the growth of _Bifidobacterium_ strains studied in in vitro conditions, juniper berry essential oil ranked second among the three tested essential oils. The highest size of the bifidobacterial growth inhibition zone observed with this essential oil was 5.6 mm (Table 2). Statistical analyses revealed that the size of growth inhibition zones depends on the _Bifidobacterium_ bacterial strain tested. The most sensitive strain was _B. animalis_ subsp. _lactis_ Bb-12. With the addition of 25% juniper berry essential oil, the size of the growth inhibition zone of the strain observed was 4.9 mm and it increased with the increase in the concentration of the essential oil. At a concentration of 50% and 75%, the average growth inhibition zone was 5.1 and 5.6 mm, respectively. A slight reduction in the growth inhibition zone was noted at a concentration of 100% and the size of the zone was 4.6 mm. However, HN 019 strains did not show sensitivity to the antibacterial effects of the juniper berry essential oil, because the average growth inhibition zones observed with the use of each concentration was 0 mm. [PERSON] et al. [50] used two species of bacteria (_E. coli_ and _S. aureus_) and one species of yeast (_C. albicans_) to determine the properties of the juniper berry essential oil and several other essential oils. The authors recorded growth inhibition zones of 14, 12, and 17 mm for _E. coli_, _S. aureus_, and _C. albicans_, respectively, using juniper berry essential oils. They observed larger growth inhibition zones of the analyzed microorganisms with the use of the juniper berry essential oil, compared to our work. This may be due to differences in the methods used for assessing growth inhibition, the sensitivity of microorganisms, and the composition of individual essential oils. [PERSON] et al. [51] analyzed the composition of the juniper berry essential oil and the antibacterial activity of this oil by the well diffusion method using _S. aureus_, _P. Aeruginosa_, and _E. coli_.