POSSIBLE RELATIONSHIP OF SUCCINATE-DEHYDROGENASE AND FATTY-ACID SYNTHETASE ACTIVITIES TO ASPERGILLUS-PARASITICUS (NRRL-5139) GROWTH AND AFLATOXIN PRODUCTION

Fatty acid synthetase (FAS) activity measured over time corresponded t o aflatoxin B-1 biosynthesis by Aspergillus parasiticus grown in minim al salts sucrose medium. Succinate dehydrogenase (SDH) activity, our p rimary metabolism indicator, decreased as FAS activity increased demon strating that as primary metabolism slows, secondary metabolism and su bsequently aflatoxin production begins. Fungal biomass, as measured by chitin, increased up to day 13 then stabilized. Calcium, potassium, m agnesium, manganese, zinc, and a combination of these minerals were te sted to determine their effect in culture on FAS and SDH activities. C ultures grown in broth supplemented with zinc had greater FAS activity and produced more aflatoxin Bi when compared to the unsupplemented co ntrol. To determine if enzyme activity in a complex substrate is alter ed due to mineral composition, peanuts were cultivated with gypsum (ca lcium sulfate) supplementation. The peanuts grown had higher calcium c ontent but less zinc. All peanuts grown in gypsum treated fields had l ess aflatoxin produced on them when compared to unsupplemented peanuts . Also, FAS activity was lower and chitin content was less when compar ed to the unsupplemented control peanuts. The FAS activity observed in these experiments indirectly suggests that the FAS complex may be res ponsible for producing the precursor for aflatoxin synthesis. However, additional information is needed to validate this hypothesis.