Effect of zinc, copper, and iron on ochratoxin A production.

The effect of zinc, copper, and iron levels on production of ochratoxin A by Aspergillus ochraceus Wilhelm in a synthetic medium in a shake culture was investigated. Optimal concentrations of ZnSO(4), CuSO(4), and FeCl(3) for ochratoxin A production were 0.055 to 2.2 mg/liter, 0.004 to 0.04 mg/liter, and 1.2 to 24 mg/liter, respectively. Zinc and copper levels greater than optimum reduced the rate of ochratoxin accumulation without altering either glutamate or sucrose utilization. Ochratoxin A production was correlated with rapid utilization of sucrose by the fungus and decreasing pH of the medium. Most of the glutamic acid was removed from the medium prior to ochratoxin production. There was no correlation between mycelial dry weight and ochratoxin A production.