PRODUCTION OF GLIOTOXIN BY GLIOCLADIUM-VIRENS AS A FUNCTION OF SOURCE AND CONCENTRATION OF CARBON AND NITROGEN
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abstract
Sources of carbon and nitrogen and the carbon:nitrogen (C:N) ratio influenced both production of gliotoxin and growth by a strain of Gliocladium virens. Higher antibacterial activity against Bacillus cereus was expressed in a defined medium amended with glucose and phenylalanine as the sources of carbon and nitrogen, respectively, than with other carbon and nitrogen sources tested. Gliotoxin extracted from the 6-day-old culture filtrate of the fungus and diluted by a factor of ten had greater antibacterial activity than four other unidentified antibacterial substances extracted from the same culture filtrate. Dynamics of mycelial growth and gliotoxin production were consistent over a range of C:N ratios (18:1, 31:1, and 42:1). Overall, as the mycelial weight of the fungus increased, the amount of gliotoxin increased up to 140 mg litre 1 of medium after 810 days of incubation. The rate of gliotoxin production (mg ml 1 ) was slower when the fungus was grown in a C:N ratio of 80:1 than in the other C:N ratios tested. Similar results were obtained when gliotoxin was recorded as mg gliotoxin per unit of mycelial weight. Maximum gliotoxin (140 mg l 1 ) was produced after eight days at all C:N ratios tested, except 80:1 for which ten days were required to produce this level of gliotoxin. The composition of the medium yielding maximum gliotoxin after eight days incubation consisted of 25 g glucose, 50 g phenylalanine, 20 g KH 2 PO 4 , 10 g MgSO 4 7H 2 O, 001 g FeSO 4 7H 2 O in 10 litre distrilled water, adjusted to pH 35 with 25% phosphoric acid. 1991, British Mycological Society. All rights reserved.
