Changes in cell wall structure of four strains of Sacccharomyces cerevisiae species (brewer's, baker's and probiotic yeast) after culturing on deproteinated potato juice water (DPJW) with diverse addition of glycerol and different pH were investigated. It allowed to select conditions intensifying biosynthesis of β(1,3)/(1,6)-glucan and mannoproteins of cell walls of tested strains. Yeast cell wall structural polysaccharides show biological activity and technological usability in food industry but also decide about therapeutic properties of yeast biomass. The highest increase in the thickness of walls (by about 100%) and β-glucan layer (by about 120%) was stated after cultivation of S. cerevisiae R9 brewer's yeast in DPJW supplemented with 5 and 10% (w/v) of glycerol and pH 7.0 while S. cerevisiae var. boulardi PAN yeast synthesized by ab. 70% thicker β-glucan layer when the pH of growth medium was equal to 5.0. The cells of brewer's yeast (S. cerevisiae R9), probiotic (S. cerevisiae CNCM 1-745) and baker's (S. cerevisiae 102) intensified the ratio of mannoproteins in the structure of cell walls cultivated in mediums supplemented with above 15% of glycerol what point out the protective action of glycoprotein's under osmotic stress conditions. The study confirms at the first time the possibility of using agro-industrial waste in biosynthesis of functional polysaccharides of S. cerevisiae cell wall. It could be an new advantage in production of yeast biomass with therapeutic properties or β-glucan preparation as a novel food ingredient.
glycerol, Saccharomyces cerevisiae, mannoproteins, β(1, waste potato juice water, 3)/(1, 6)-glucan
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Aspergillus fumigatus mitogen-activated protein kinases (MAPKs) are involved in maintaining the normal morphology of the cell wall and providing resistance against cell wall-damaging agents. Upon cell wall stress, cell wall-related sugars need to be synthesized from carbohydrate storage compounds. Here we show that this process is dependent on cAMP-dependent protein kinase A (PKA) activity and regulated by the high-osmolarity glycerol response (HOG) MAPKs SakA and MpkC. These protein kinases are necessary for normal accumulation/degradation of trehalose and glycogen, and the lack of these genes reduces glucose uptake and glycogen synthesis. Alterations in glycogen synthesis were observed for the sakA and mpkC deletion mutants, which also displayed alterations in carbohydrate exposure on the cell wall. Carbohydrate mobilization is controlled by SakA interaction with PkaC1 and PkaR, suggesting a putative mechanism where the PkaR regulatory subunit leaves the complex and releases the SakA-PkaC1 complex for activation of enzymes involved in carbohydrate mobilization. This work reveals the communication between the HOG and PKA pathways for carbohydrate mobilization for cell wall construction.IMPORTANCE Aspergillus fumigatus is an opportunistic human pathogen causing allergic reactions or systemic infections such as invasive pulmonary aspergillosis, especially in immunocompromised patients. The fungal cell wall is the main component responsible for recognition by the immune system, due to the specific composition of polysaccharide carbohydrates exposed on the surface of the fungal cell wall called pathogen-associated molecular patterns (PAMPs). Key enzymes in the fungal cell wall biosynthesis are a good target for fungal drug development. This report elucidates the cooperation between the HOG and PKA pathways in the mobilization of carbohydrates for fungal cell wall biosynthesis. We suggest that the reduced mobilization of simple sugars causes defects in the structure of the fungal cell wall. In summary, we propose that SakA is important for PKA activity, therefore regulating the availability and mobilization of monosaccharides for fungal cell wall biosynthesis during cell wall damage and the osmotic stress response.
cell wall, glycogen, Trehalose, Aspergillus fumigatus, MpkC, SakA, high-osmotic glycerol pathway, protein kinase A
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Anthocyanins are being explored as natural food colorants thanks to their diverse color portfolio. However, the main challenge for food industry application is their instability and pH-associated color change which occurs in majority of the foods containing natural pigments. Anthocyanin-derived pigments pyranoanthocyanins are being largely investigated as stable natural food colorants, since they are resistant to pH, SO2 or ascorbic acid. In this study two experimental approaches were compared for the synthesis of pyranoanthocyanin vitisin A and three vinylphenolic pyranoanthocyanins (malvidin-3-O-glucoside-4-vinylcatechol, malvidin-3-O-glucoside-4-vinylphenol, and malvidin-3-O-glucoside-4-vinylguaiacol). Synthesis of pyranoanthocyanins with artificial ageing of model wine solution at 30 °C was compared to the fermentation of model grape must with yeasts. Both model solutions contained Vitis vinifera L. cv. Pinot Noir anthocyanin skin extract. The fermentation with the yeast Pichia guilliermondii ZIM624 showed higher potential for the production of vinylphenolic pyranoanthocyanins in comparison to artificial ageing at 30 °C. The results show a 50-fold higher yield of malvidin-3-O-glucoside-4-vinylphenol obtained by fermentation in comparison to artificial ageing. In contrast, artificial ageing of model wine produced higher yield of vitisin A (21.3%) while fermentation with P. guilliermondii ZIM624 produced this pyranoanthocyanin to a lesser extent (1.1%). The vitisin A yield in fermentations with six other yeast strains was lower than 4%. Produced pyranoanthocyanins were isolated with semi-preparative HPLC–DAD and identified with HPLC–PDA–MS3. The color of pyranoanthocyanin methanol fractions ranged from orange to pink, to light purple.
fermentation, yeasts, pyranoanthocyanins, anthocyanins, food colorants
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