Growth and Pigmentation of Aspergillus Umbrosus

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Abstract
Under a wide range of cultural conditions from 40 to 70% of the dry weight material produced by A. umbrosus in liquid cultures consists of pigments. Optimum conditions for pigment synthesis in Czapek-Dox mineral salts solutions are as follows: surface cultures, initial pH 5.5, temperature of 20–24 C, and a glucose concentration of 10–20%. Sucrose, glucose, mannose and xylose are preferred carbon sources for growth and pigment production. Glycerol consistently produced the highest yields of pigment per gram of mycelium. Starch is a poor carbon source. Both ammonium and nitrate ions serve as nitrogen sources for A. umbrosus. Increasing nitrogen content of the medium does not necessarily increase growth or pigment production. At the concentrations tested some stimulation of pigment production by nitrogen sources is due to osmotic or salt balance effects rather than to differences in the nitrogen level supplied. Small NaCl concentrations stimulate growth and pigment production by A. umbrosus. Larger NaCl concentrations (10-20%) are toxic and inhibit growth. Flavoglaucin, auroglaucin and erythroglaucin have been identified in pentane extracts of mycelial mats. Following pentane extraction, further extraction with benzene and then with acetone results in two additional fractions containing relatively large amounts of pigments. At least five different pigments are involved. Further studies on these pigments are in progress at the present time.

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