Figure 5.

The β-GD derived from the hydrolysis of B. sorokiniana EPS matrix exhibits antioxidative properties. A, Glycosidic linkage analysis of B. sorokiniana EPS matrix and CW preparations. 2,3-hexopyranose, 2,3,4- hexopyranose, and 2,3,6- hexopyranose are abundant in the EPS matrix, whereas 4-glucose is abundant in the CW of B. sorokiniana. The experiment was performed with three independent biological replicates of Bs EPS and Bs CW and the TIC from one of the replicates is represented. B, Analysis of digested EPS or CW fractions by MALDI-TOF mass spectrometry. The 1,661-Da β-GD corresponding to 10 hexoses is released from the EPS matrix but not from the CW of B. sorokiniana. The representative DP of hexoses is indicated on top of the m/z (M+Na)⁺ masses of oligosaccharides. The digestion of Bs EPS with HvBGLUII was repeated independently three times with a similar result and the digestion of Bs CW with HvBGLUII was performed once. C, ROS burst assay was performed on barley roots treated with Milli-Q water (mock), chitohexaose (25 µM), Bs β-GD (300 µM), or a combination of chitohexaose and Bs β-GD. Boxplots represent total cumulative ROS accumulation over a measured time interval of 25 min. Each data point in the boxplot represents the integrated value from an individual well (center line, median; box limits, upper and lower quartiles; whiskers, 1.5× interquartile range). The experiment was performed three times with similar results. Statistically significant differences are indicated by different letters based on a one-way ANOVA and Tukey’s post hoc test (significance threshold: P ≤0.05). Bs, Bipolaris sorokiniana; DP, degree of polymerization; p, pyranose. ^aexact sugar moiety unknown; overrepresentation of linkages due to undermethylation cannot be excluded.