Aspergilli as Ochratoxin Producers

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Abstract
To determine whether ochratoxin is produced by species of Aspergillus other than A. ochraceus, 44 strains representative of the nine species composing the A. ochraceus group were grown on both pearled wheat and cracked corn in duplicate shaken flasks at 28 C for 5 days. Rice was a poor substrate for production of ochratoxin. Molded substrates were extracted with acetonitrile-water; partially purified extracts were assayed for ochratoxins by thin-layer chromatography. All positive samples were confirmed by solubility in sodium bicarbonate and the preparation of methyl esters. Ochratoxins A and B were found in some strains of A. sulphureus, A. sclerotiorum, A. alliaceus, A. melleus, A. ochraceus, A. ostianus, and A. petrakii. No ochratoxin was produced by the one strain of A. elegans or any of six strains of A. auricomus. Five of nine strains of A. sclerotiorum and five of 11 strains of A. ochraceus were negative. All seven strains of A. alliaceus were positive, but one was at a very low level. Generally, yields of ochratoxin were higher in wheat than in corn. Occasionally, as much ochratoxin B was produced as A. Highest yields of ochratoxins A and B were obtained from respective strains of A. ochraceus NRRL 3174 and NRRL 3519. Some strains of most species of the A. ochraceus group produce this mycotoxin as a secondary metabolite.