Heavy metal tolerance of Aspergillus piperis using the agar well diffusion method

Abstract

A lead resistant strain of Aspergillus piperis, a subgroup of A. niger with known heavy metal remediation properties, was tested for heavy metal resistance. The agar well diffusion method was used with metal solutions containing 2000 ppm of copper (Cu(II)), iron (Fe(II)), lead (Pb(II)), magnesium (Mg(II)), manganese (Mn(VI)), selenium (Se(VI)), cadmium (Cd(II)), and zinc (Zn(II)) ions, respectively. Of the metals tested, A. piperis only exhibited substantial growth inhibition in Cd(II) up to 23 mm from the well center, while simultaneously completely inhibiting spore formation. Lesser inhibition was observed in Se(IV), Pb(II), and Zn(II) of which the latter two exhibited evidence that additional metal resistance was developed during incubation. After five days the fungus had successfully grown in the presence of all the other metals, making A. piperis a promising candidate for heavy metal mycoremediation research.