Effect of pH and organic matter on the toxicity of heavy metals to growth of some fungi.

Increasing the pH from 5 to 9 decreased the toxicity of mercuric chloride, zinc sulfate, lead nitrate, copper sulfate and nickel chloride toward the growth of Aspergillus flavus, Penicillium chrysogenum, Cunninghamella echinulata, Myrothecium verrucaria and Phoma humicola. On the other hand, the toxicity of cadmium chloride was increased by the increasing pH. Also increasing the concentration of organic matter (peptone and yeast extract) from 0.5 to 1.5% induced a significant reduction in the toxicity of all heavy metals toward the growth of all test fungi.