Growth of and Aflatoxin Production by Aspergillus parasiticus in a Medium Containing Potassium Chloride or a Mixture of Potassium Chloride and Sodium Chloride

Twenty-five milliliters of glucose-yeast-salts medium containing 0, 2, 4, 6, 8 and 10% KCl or a mixture of NaCl (%) and KCl (%) (0:0, 1.5:0.5, 3.25:0.75, 4.75:1.25, 6.5:1.5, and 8:2) was inoculated with 1 ml of a spore suspension containing 106 conidia of Aspergillus parasiticus NRRL 2999 and incubated at 28°C for 10 d. The pH, dry weight of mycelium and aflatoxin production were determined after 3, 7 and 10 d of incubation. Amounts of aflatoxin produced were determined using reverse-phase high-performance liquid chromatography (HPLC). The mold growing in the presence of 0, 2 and 4% KCl produced maximum amounts of aflatoxin after 3 d, whereas in the presence of 6, 8 and 10% KCl it did so after 7 d. This trend was also true when the mold grew in the presence of mixtures of NaCl and KC1. Amounts of aflatoxin produced decreased with increasing concentrations of KCl or of the mixture of NaCl and KCl. The mycelial dry weight increased with increasing concentrations of KCl or the mixture of NaCl and KCl, although there was an extended lag phase at higher concentrations of both treatments.