## 3 Results and Discussion
### _Trehalose and Glycogen Concentration_  
Literature data show that trehalose is one of the main reserve carbohydrates in _S. cerevisiae_ yeast cells and can constitute up to 23% or more of cell dry matter depending on growth conditions and life cycle stage [39]. [PERSON] et al. [40] demonstrated that trehalose exhibits one more significant activity for yeast, is a protective agent, stabilizes proteins and cell membranes and protects against various stress conditions such as heat shock, dehydration and oxidative and ethanol stresses. Work on cell protection and improved viability by trehalose led to the use of dried yeast in brewing [41]. In the presented study, the trehalose content depended on the strain of brewing yeast and rehydration medium. Yeast strains _Sc_ T58, _Sc_ US-05 and _Sp_ W30/70 were characterized by a similar level of trehalose, while a significantly higher content of trehalose was observed in the case of _Sc_ S33 strain. As previously described, this culture had the lowest cell viability. Therefore, it can be assumed that it was influenced by the most severe stress factors. This is confirmed by the amount of trehalose accumulated, which is a measure of environmental stress factors. Significant differences were also observed depending on the water used for rehydration. For all analyzed ale strains, rehydration with plasma-treated waters (PTWs) caused a decrease in trehalose content, which may also prove that PTWs are not a stress factor for yeast cells. These results confirm that the trehalose content in yeast dependsnot only on yeast strain, but also on the storage conditions and rehydration medium. The trehalose content increases in yeast cells under stress conditions. _Saccharomyces pastorianus_ yeast is more sensitive than _Saccharomyces cerevisiae_ yeast, which is why it can react to a stress factor of lower intensity [23]. After completion of the fermentation process, the highest content of trehalose was observed for the poor quality yeast strain of _Sc_ T58 (11.4%), and the lowest for the fresh yeast strain of _Sc_ US-05 (4.17%). This may indicate that the fresh yeast was more resistant to stress and did not accumulate more trehalose in cells. There is ample evidence to suggest that increased stress tolerance is associated with the accumulation of trehalose. Furthermore, dried yeast also has an increased content of trehalose due to the stress during the drying process. In the case of samples fermented with yeast after rehydration, in the presence of PTWAir, the highest content of trehalose was obtained for the poor quality strain of _Sp_ W30/70, and the lowest for the fresh strain of _Sc_ US-05 and poor quality yeast strain of _Sc_ S33 (Table 3). Due to rehydration in the presence of PTWN, the highest content of trehalose was observed in the fermented samples of poor quality yeast strains of _Sc_ T58 and _Sp_ W30/70. The fresh yeast strain of _Sc_ US-05 had the highest content of trehalose in the samples using PTWN (8.32%), compared to the control sample (4.17%). Significant differences were observed depending on the water used for rehydration. For all analyzed a strains, rehydration with plasma-treated waters (PTWs) caused a decrease in trehalose content, which may also prove that PTWs are not a stress factor for yeast cells. Glycogen is the main polysaccharide stored in brewing yeast, accounting for up to 40% (\(w/w\)) of dry cell matter. The amount of glycogen depends on the yeast strain and many variables related to yeast storage and other factors [42]. The importance of glycogen reserves for survival during prolonged nutrient deficiency has been clearly demonstrated in yeast [43]. Furthermore, yeast cells that can accumulate more glycogen reserves have a growth advantage over other cells in the environment, which suggests that glycogen can contribute to overall fermentation efficiency [44]. Table 2 shows the glycogen content for all analyzed yeast strains. Statistically significant differences in the level of glycogen between the analyzed strains were found ranging from 7.37% to 18.9%.