Aflatoxin formation, lipid synthesis, and glucose metabolism by Aspergillus parasiticus during incubation with and without agitation

Abstract

Glucose utilization, growth of mold, and synthesis of aflatoxin and total lipid by Aspergillus parasiticus were studied with cultures that were incubated statically and with agitation. With both cultural conditions, maximal toxin formation occurred at 5 days which coincided with the end of rapid mold growth and rapid uptake of glucose. The toxin concentration decreased as incubation continued. The pattern for formation and depletion of total lipid was similar to that for aflatoxin. Maximal yields of toxin and of total lipid did not coincide with maximal production of mold mycelium. Incubation with agitation enhanced mold growth, consumption of glucose, and production of aflatoxin and total lipid during the first 3 days. Generally, more growht occured in agitated cultures, but maximal yields of aflatoxin and total lipid were lower than in quiescent cultures. The need for limited, but not excessive, O 2 for synthesis of aflatoxin and lipid also was demonstrated by varying the volume of medium in flasks that were incubated quiescently. Incorporation of [1- 14C] glucose into aflatoxin indicated that limiting the O 2 supply and thereby favoring glucose catabolism via the Embden-Meyerhof pathway enhanced toxin formation. Aflatoxin formation also was greater when oxidative respiration of the mold was restricted by a metabolic inhibitor. Results suggest that the degree of aeration of the culture is important in controlling biosynthesis of aflatoxin.