Influence of pH Alone and in Combination with Phenolic Antioxidants on Growth and Germination of Mycotoxigenic Species of Fusarium and Penicillium

Abstract

The effect of pH alone and in combination with two phenolic antioxidants on mycelial growth and conidial germination of mycotoxigenic fungi was examined. The mycotoxigenic fungi studied included seven members each of Fusarium and Penicillium genera. The present study was carried out at pH 4, 6, 8, and 10 alone and in the presence of 100 and 200 μg/ml of butylated hydroxyanisole (BHA) and propyl paraben, respectively. All of the test fungi examined were able to grow at pH 4, 6, 8, and 10 on potato dextrose agar. The majority of the Fusarium species, with the exception of Fusarium graminearum, were tolerant of acid and alkaline pHs. Two of the Penicillium species were rapid growers and were tolerant of acid and alkaline pHs. The tolerance of the slower growing Penicillium species varied in their response to acid and alkaline pHs. Conidial germination was partially inhibited in all of the Fusarium and Penicillium species in the presence of 100 μg/ml of BHA at all pH levels. However, in the presence of 200 μg/ml of BHA, there was complete inhibition in conidial germination for four of the Fusarium species at pH 4, 6, 8, and 10. Propyl paraben, at the four pH levels, completely inhibited conidial germination in Fusarium species and all but one species of Penicillium at 200 μg/ml. Reduction in colony diameter for the majority of Fusarium and Penicillium species, at all pH levels was observed at 100 and 200 μg/ml of BHA. However, at 200 μ/ml of Propyl paraben, mycelial growth was completely inhibited for the majority of the Fusarium and Penicillium species at the four pH levels.