## 3 Results and Discussion
### \(\beta\)-Glucan Content  
The \(\beta\)-glucan was extracted from the optimal sample with the highest degree of cell rupture and showed a value of 78.53% (Figure 5a), which was higher than the results obtained by [PERSON] et al. (2014) for \(\beta\)-glucan extracted from _S. cerevisiae_ baker yeast in similar conditions. The \(\beta\)-glucan extraction yield is directly influenced by yeast conditioning and lysis method. [PERSON] et al. (2003) reported \(\beta\)-glucan contents between 50.5 and 71.2%, depending on the yeast strain, the highest value being that of spent brewer's yeast [22]. The data presented by [PERSON] and [PERSON] (2009) showed lower values of \(\beta\)-glucan (29.5-38.1%) extracted from spent brewer's yeast cells lysed by the bead milling method compared to our study, most likely because of bead diameter (12 mm), the different material (stainless steel),and an intermittent mixing process [31]. To observe if there were any significant differences from the optimal sample, further investigations were conducted on the yeast samples at the lowest concentration of 5% with different degrees of cell rupture at three different vortexing cycles and yeast/glass bead ratios. Thus, by using the alkaline-acid method described in Section 2.3 on samples with disruption efficiencies between 34.8 and 99.8%, the \(\beta\)-glucan content was determined. The results of the effect of cell breakage efficiency on \(\beta\)-glucan content (Figure 5a) indicates that incomplete cell rupture leads to a decrease in \(\beta\)-glucan after the alkaline-acid extraction (67.38% \(\beta\)-glucan at a disruption efficiency of 34.8% compared to 78.53% \(\beta\)-glucan at 99.8% cell breakage).This is mainly due to an incomplete extraction achieved by cells that still  
Figure 4: The degree of cell rupture. Three representative samples with a yeast/glass bead ratio of 1:2 at different vortexing cycles (1\(\times\), 2\(\times\), and 3\(\times\)) and yeast concentrations (5%, 10%, and 15%) are shown: black arrows indicatehe broken cells with irregular cell walls and red arrows show dead cells stained inside with methylene blue. No living cells were present (400\(\times\) magnification). (**a**) 15% yeast suspension; 1:2 yeast/ glass bead ratio; 1\(\times\) vortexing cycle (15.1%). (**b**) 10% yeast suspension; 1:2 yeast/glass beads ratio; 2\(\times\) vortexing cycles (41.6%). (**c**) 5% yeast suspension; 1:2 yeast/glass beads ratio; 3\(\times\) vortexing cycles (99.8%). have intracellular content after the lysis procedure (these cells are indicated by red arrows in Figure 4). [PERSON] et al. (1969) noted that the extraction process is made more difficult when using the whole cells in alkali-extractions because of remaining residues from the cell contents [32]. Additionally, Figure 5b shows significant correlation (\(R^{2}\) = 0.93) between the disruption efficiency and \(\beta\)-glucan content after the alkaline-acid extraction protocol and supports the assumption that a high degree of cell breakage will provide a large amount of \(\beta\)-glucans. The molecular characteristics of the \(\beta\)-glucan extracted from spent brewer's yeast after optimization of cell lysis is shown in Figure 6. The polysaccharide absorption band can be observed at 3330.31 cm\({}^{-1}\), while the peak at 2918.23 cm\({}^{-1}\) could be given by the C-H stretching vibrations of the CH\({}_{2}\) and CH\({}_{3}\) groups [33]. These data are in agreement with those reported by [PERSON] et al. (2009). The particular bands are attributed to the axial deformation of OH, being also characteristic for \(\beta\)-D-glucans in addition to the vibrations of the CH bonds, the peak at 2918.23 indicating the frequencies of the functional groups of these polysaccharides. The absorption band found at 1635.26 cm\({}^{-1}\) can be caused by the stretching vibrations of C=O groups.