Carbohydrate Content of Fungal Humic Acid-type Polymers (Melanins)
1979
Linhares, L. F. | Martin, J. P.
The carbohydrate contents of a variety of fungal humic acid-type melanins ranged from 1.1 to 5.9%. Values were 1.7 to 2.6% for soil humic acids and 0.4% for Leonardite peat humic acid. Fungal culture medium polymers not precipitated by acid and fungal cells contained from 12 to 55% carbohydrates. The uronic acid content of all products was very low, ranging from essentially zero (not detected) to 1.1%. Stachybotrys atra was the only fungus where uronic acids were detected in all samples. Uronic acids were, however, present in all soils, the values ranging from 0.3 to 0.4%. Recovery of uronic acids after acid hydrolysis using galacturonic acid as a check gave low values. The necessity of eliminating interferring substances before the colorimetric determination of sugars and uronic acids in soil and fungal polysaccharide hydrolysates was demonstrated. Thin-layer chromatography of concentrated hydrolysates from the humic acid-type fungal melanins and soil humic acids showed the presence of glucose, galactose, mannose, and xylose in most of the samples. A mass spectrum of the pyrolysis fragments of Aspergillus glaucus sp. humic acid-type polymer showed definite series peaks related to polysaccharides, the most prominent, however, were related to proteins and phenolic substances.
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