Comparison of Growth of Aspergillus flavus and Aspergillus parasiticus in Different Conditions of Temperature, Moisture and pH

Aspergillus parasiticus and Aspergillus flavus are the most important agents for contamination of food and are capable of production of carcinogenic toxins. Increasing awareness of optimal growth conditions helps to control and prevent the contamination and toxicity of these fungi. This experiment was conducted in order to study the effect of temperature, pH and seed moisture content on the growth of these fungi. The effect of corn seed moisture, at levels 15, 18, 21, 24, 27 and 30 percent on corn, and temperature, at level 18, 22, 25, 28, 31 and 34 °C, in PDA medium and the effect of pH at level 3, 4, 5, 6 and 7 in PDB medium were investigated on the growth of these two fungi. The growth rate of fungi and dry weight of mycelium fungi in different treatments was evaluated in a completely randomized design in four repetitions. Statistical analysis was performed by using SAS 9.1 software. Also, to determine the presence of toxins in fungi was used of coconut–agar medium. The results showed that the optimum growth conditions are for A. parasiticus at 31°C, pH= 5 and seed moisture content of 27% and for A. flavus at 28°C, pH=6 and seed moisture content of 27%. It was also found, both fungal have the ability to produce aflatoxin. According to the results of this research can be concluded that A. parasiticus and A. flavus have the better grow in tropical and subtropical regions and decrease moisture content, low temperatures and cool in stock can play an effective role in preventing the growth of these fungi and in reducing their toxin production consequently.