## 4 Discussion  
Kefir grains are rich in potentially probiotic microorganisms, and it is established that they exhibit noteworthy health-promoting properties [28]. _P. acidilactici_ ORE5, isolated from keir grains, was initially screened for potential probiotic properties, and adequate survival rates at low pH were observed. This is an important finding, as a candidate probiotic strain should persist at pH 3.0 or even lower [18]. Furthermore, it exhibited resistance to pancreatin and bile salts. Pancreatin and bile salts are considered important parameters regarding food digestion. Specifically, pepsin is an enzyme that catalyzes protein digestion, while pancreatin contributes a significant role in lipid metabolism. On the other hand, bile  
Figure 3: Relative abundances (%) of different bacterial genera, after 16S rRNA NGS sequencing in the Katiki Domokou-type cheese samples. All data represent the mean values from two independent experiments. Genera with percentages <0.5% are represented as “others”. KC—control samples, KFP—cheese samples containing free _P. acidilactici_ ORE5 cells, KIP—cheese with immobilized _P. acidilactici_ ORE5 cells on pistachio nuts. salts assist in the digestion and absorption of fats. Likewise, all the above are significant requirements for probiotic efficiency [29]. Regarding antibiotic susceptibility, resistance to tetracycline and clindamycin was monitored, which is also in agreement with the study of [PERSON] et al. [30], while resistance to erythromycinincn has also been reported by [PERSON] et al. [31]. However, these reports are few in the literature, and they lack information about the resistance character (intrinsic or acquired). Meanwhile, the demand for functional foods containing probiotic cells is growing as consumer awareness about the positive impact of probiotics on health is increasing. Notably, the incorporation of probiotics in dairy products is already common, as it has been suggested that milk functions as a buffering agent, protecting bacteria during the passage through the GI tract [20]. In addition, cell immobilization on food carriers may improve this protective effect, resulting in high cell viability. Pistachio nuts have been previously evaluated as natural carriers, and the positive impact of the consumption of pistachio nuts fortified with probiotic cells on the lipid profile of diabetic rats was recently reported [3,8]. In this vein, our strategy involved the incorporation of immobilized _P. acidilactici_ ORE5 cells on pistachio nuts in the Katiki Domokou cheese and the evaluation of the potential effect of immobilized probiotic cells on the cheese microbiome. Katiki Domokou is a soft cheese made from goat's and ewe's milk and, owing to its pH (4.3-4.5), may be considered a suitable food carrier for probiotic cells to maintain high cell viability during storage and after consumption. This suggestion has been corroborated by the high cell loads of _P. acidilactici_ ORE5 cells achieved during refrigerated storage of cheese, as lactobacilli levels were >8.5 logcfu/g up to 7 days of storage. The incorporation of immobilized probiotic cells resulted in higher cell viability compared to the cheese sample fortified with free cells, indicating the positive impact of cell immobilization on the maintenance of high cell loads. These results are in accordance with previous studies that demonstrated the enhancement of cell survival by cell immobilization [4,32,33]. Indeed, the incorporation of immobilized _L. casei_ ATCC 393 on apple pieces and casein in yoga resulted in cell loads > 7 logcfu/g up to 28 days of storage [32], while [PERSON] et al. (2022) reported that soft cheese with immobilized _L. paracasi_ cells on wheat bran exhibited high cell loads (>7.5 logcfu/g) after 30 days of storage [33]. Of note, a significant increase in lactobacilli numbers was observed up to 3 days of storage, which may be attributed to the ability of lactobacilli to adapt well to the milk environment [32]. Furthermore, in accordance with our results, [PERSON] et al.