Polysaccharides of Molds and Yeasts

Although polysaccharide metabolic products of molds and yeasts are not strictly bacterial polysaccharides, they are considered briefly here because of similarities in chemical structure (see also page 191). 

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This review deals with bacterial and related polysaccharides, such as those of molds and yeasts. The bacteriological nomenclature is that of Bergey10 non-systematic nomenclature is indicated by ( ). 

Agar, which is low in metabolizable or inhibitory substances, debris, and thermoduric spores, is ideal for the propagation and pure culture of yeasts, molds, and bacteria. Agar also meets the other requirements of ready solubiUty, good gel firmness and clarity, and a gelation temperature of 35—40°C and a gel melting temperature of 75—85°C. A clarified and purified form of the bacterial polysaccharide, geUan gum, is the only known satisfactory substitute. 

It is difficult to state whether formation of exocellular polysaccharides is more prevalent among the bacteria, the yeasts, or the molds. However, with bacteria, polysaccharide formation has been studied the most thoroughly. Several yeasts are known to elaborate exopolysaccharides and are excellent sources thereof. Polysaccharide formation by fungi is less frequently observed. However, species of... 

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