## 3 Results
### The Influence of Physicochemical Parameters on Free and Encapsulated Lactobacillus casei Bacteria
The average values of LAB cell reduction were 1.08-3.06 log after 15 min, 2-4.22 log after 30 min and 3.23-8.7 log after 60 min for the above samples. The lowest reductions of live cells were found in microsphere sample 1 and were 0.1 log after 15 min, 1 log after 30 min and 1.9 log after 60 min. The greatest cell reduction in the case of contact with pH = 5.5 (Figure 2B) was observed for the suspension of free _L. casei_ cells, microsphere sample 1 and microdispersion 4. The reduction values of _L. casei_ cells were within the ranges of 0.1-0.6 log after 15 min contact, 1-1.54 log after 30 min contact and 1.9-2.13 log after 60 min contact for the above-mentioned samples. The minimal reductions in LAB cells were observed for microsphere samples 2 and 3 and were in the ranges of 0.06-0.24 log after 15 min, 0.12-0.34 log after 30 min and 0.32-0.52 after 60 min. The greatest tolerance to pH 9 (Figure 2C) after contact times of 15, 30 and 60 min was demonstrated by microsphere sample 2, for which the recorded decreases in LAB  
Figure 3: The effect of (**A**) UV radiation and (**B**) preservative on free and encapsulated _Lactobacillus casei_ bacteria. viability were 0.17 log after 15 min, 0.23 log after 30 min and 0.33 log after 60 min. For the suspension of free LAB cells and the remaining samples (1, 3 and 4), the LAB reduction values were within the ranges of 0.78-5.48 log after 15 min, 1.14-7.70 log after 30 min and 3.17-8.9 log after 60 min. The next parameters were the effect of UV radiation and the preservative system on free and encapsulated _L. casei_. The exposure time of UV radiation was selected according to the methodology of [PERSON] et al. [43] for comparative purposes, in which as a result of 6 h exposure to UV light, there was complete elimination of probiotic strains. In the case of tests, the UV exposure was extended to 24 and 48 h in order to illustrate the effectiveness of the carriers used on the probiotic _L. casei_ strain. However, in the case of the effect of a preservative, this is the first study to check the effect of carriers containing microspheres with potential use in cosmetic products; therefore, the action time was selected experimentally. The maximum exposure time was 60 min, as this was the longest survival time of the free strain. UV radiation after exposure times of 24 and 48 h had the most adverse effect on free _L. casei_ cells, reducing the number of live cells by 6.34 log after 24 h and by 7.90 log after 72 h. The greatest decrease in the viability of encapsulated LAB bacteria was observed in microsphere sample 1 (0.4 log after 24 h and 1.69 log after 48 h) and microdispersion 4 (1.33 log after 24 h and 2.59 log after 48 h). In microsphere samples 2 and 3, the numbers of live cells which were decreased after 24 and 48 h were minimal and amounted to 0.14 log and 0.5 log (microsphere sample 2) and 0.2 log and 1.54 log (microsphere sample 3), respectively. The influence of the preservative system (sodium benzoate combined with sodium salts of levulinic and anisic acid), which was initially selected as a system that protects the cosmetic against microbiological degradation, was also assessed. The assessment was made after a contact time of 30 and 60 min. The greatest reductions in bacterial cells were observed in the case of the free _L. casei_ cell suspension and were 7.70 log after 30 min and 8.90 log after 60 min. The effects of the preservative system after both contact times in the case of microsphere samples 2 and 3 were relatively small, causing decreases in cell number of 0.62 log after 30 min and 1.7 log after 60 min (microsphere sample 2) and 1.3 log after 30 min and 1.72 log after 60 min (microsphere sample 3). For microsphere sample 1, the LAB reductions were 1.24 log after 30 min and 2.80 log after 60 min, and for microdispersions, 4-1.33 log after 30 min and 3.31 log after 60 min. Microsphere sample 2 was characterised by the best survival of _L.