Ammonium Bicarbonate Inhibition of Mycotoxigenic Fungi and Spoilage Yeasts

Sodium bicarbonate inhibits growth and aflatoxin production by Aspergillus parasiticus . This survey determined that other mycotoxigenic fungi were also sensitive to bicarbonates. Sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, ammonium sulfate, and sodium chloride were added to buffered or unbuffered potato-dextrose agar to determine the bicarbonate effect on growth and morphology of six mycotoxigenic fungi. Three nonmycotoxigenic fungi and four yeast species were also examined. Ammonium bicarbonate at 0.11M completely inhibited the growth of Fusarium tricinctum NRRL 13442, F. tricinctum NRRL 13426, F. graminearum NRRL 5883, F. sporotrichioides NRRL 3249, Penicillium griseofulvum NRRL 989, Aspergillus ochraceus NRRL 3174, A. flavus NRRL 1957, A. niger , and P. notatum . Sodium chloride and pH elevated through the use of ampso-NaOH, capso-NaOH, or glycine-NaOH buffer did not display an inhibitory effect on the filamentous fungi examined. Buffered ammonium sulfate treatments (pH approximately 9.0) completely inhibited all of the mycotoxigenic fungi, but at pH 5.6, ammonium sulfate treatments were not inhibitory. Sodium bicarbonate (0.11M) was effective only against P. griseofulvum , A. flavus NRRL 1957, A. niger , and P. notatum , causing viability reductions of 5.6, 3.7, 4.9, and 2.9 log cycles, respectively. Potassium bicarbonate was generally as inhibitory as the sodium salt. In contrast, elevated pH, alone, appeared to account for the >6 log reduction observed for the yeasts Lipomyces starkeyi , Geotrichum candidum , Kluyveromyces marxianus , and Debaryomyces hansenii .