# Impact of Lactic Acid Bacteria on Immunoreactivity of Oat Beers
## 3 Results and Discussion
It is evident that only intact gliadin-derived immunogenic peptides that persist throughout digestion can stimulate an immune response [45]. With the use of rabbit antibodies, the immune response of digested bottom- and top-fermented beers obtained from regular and sour oat malt was evaluated and compared with the results for barley beers as a reference sample (Figure 5). Immunogenic properties of gluten are localized within proline- and glutamine-rich sequences [27; 28]. Due to the presence of a high percentage of proline and glutamine in gluten, its digestion by human gastrointestinal digestive enzymes is challenging [38]. However, according to most literature data [60; 61; 62; 63], the products of enzymatic digestion may show a lower immunoreactivity than the initial proteins. On the other hand, according to some findings, this response may also increase, because cereal proteins digested in the gastrointestinal tract can be a source of allergenic peptides [64]. [PERSON] and [PERSON] [65] found that digestion of gliadins and glutenins with pepsin results in the formation of highly allergenic proteins with a molecular weight of 15-100 kDa. Similar conclusions were reached by [PERSON] et al. [66] after digestion of wheat products with pepsin and pancreatin. This result is likely due to the enzymatic hydrolysis of high-molecular-weight proteins, such as \(\alpha\), \(\beta\), \(\omega\), and \(\gamma\) gliadins, leading to lower-molecular-weight proteins and peptides [30]. Analysis of the gluten fraction during simulated in vitro digestion [45] showed that immunogenic peptides were absent in the gastric phase but were rapidly released from the food matrix upon entering the intestinal phase. Some of them underwent rapid proteolysis in the intestinal phase, suggesting they may not play a role in celiac disease, but at the same time, the relatively high abundance of peptides indicates a complex digestive mechanism. In this study, after performing simulated digestion, the remaining immunoreactivity values of all the tested beers, both those made from barley and oat malls, were reduced by approximately 20% in relation to the undigested beers, while maintaining statistically significant differences for barley beer and oat beer made from sour malt (\(p\) < 0.05). The immune response of the latter did not exceed 1.5% of the wheat immunoreactivity, while the remaining immunoreactivity of barley beers ranged from 1.7% to 2.7%. Although the level of toxic sequences was reduced in all the samples, the tested beverages still retained their immunogenic potential. The inability of gastric and pancreatic proteases to cleave completely proline-glutamine bonds leads to the formation of peptide fragments capable of crossing the small intestinal epithelial barrier and evoking an adverse immune response [67]. It is worth emphasizing, however, that beers produced from sour oat malt were characterized by a significantly reduced content of gluten epitopes. This suggests that the lactic fermentation process has a positive effect on reducing the immunoreactivity of the raw material, which may be associated with the ability of lactic acid bacteria to produce proline peptidases, which hydrolyze peptide bonds formed with proline. The degradation of these bonds increases tolerance to gluten [5; 37; 38; 43; 68]. In vitro and in vivo studies demonstrate that some LAB species are capable of hydrolyzing gluten proteins. A key role in this process is played by bacterial endopeptidase, which digest toxic gluten epitopes [31]. Analogous examination of beers digested in vitro was performed using sera from patients with celiac disease containing antigliadin antibodies (Figure 6). Analysis of the results obtained proves that the immune response to the tested beers is very diverse and specific to each patient suffering from celiac disease. This is related to individual sensitivity to proteins present in gluten, but also to the inefficiency of intestinal peptidases to degrade immunogenic epitopes [38; 69].