Electron microscopic study of purified polysaccharide components glucans and mannan of the cell walls in the yeast Saccharomyces cerevisiae

In this study electron‐microscopic characteristics of platinum shadowed or negatively stained preparations of purified β‐(1 → 3)‐d‐glucan, β‐(1 → 6)‐d‐glucan, and mannan were examined. These polysaccharides were isolated from cell walls of the yeast Saccharomyces cerevisiae. While purified samples of β‐(1 → 6)‐d‐glucan and mannan proved to be amorphous in structure and homogenous in appearance, the purified β‐(1 → 3)‐d‐glucan, isolated and presented to us as alkali‐insoluble yeast glucan A2, was not homogenous. It consisted of (i) fibrillar component, (ii) amorphous matrix, and (iii) chitin bud scars. The ultrastructure of β‐(1 → 3)‐d‐glucan present in the glucan A2 sample did not change after treatment with 0.5 m acetic acid at 75°C for 2 hours. After treatment with 1 m NaOH for 3 days at 4 °C scar material was removed by centrifugation and after a subsequent acidification of supernatant with acetic acid both the microfibrillar and the amorphous components were still present. It was concluded that β‐(1 → 3)‐d‐glucan component consists of molecules probably differing in their physico‐chemical properties such as D. P., the degree of branching, conformation, and that cannot be separated by the methods currently used for their isolation.