Abstract

This study assessed the growth and metal tolerance of fungal species from water and soil samples impacted by solid wastes in Ibadan, Nigeria. Isolated fungi species were exposed to two metals each (pb 100 to 600 and Co 50 to 300 mgl^-1; Fe100 to 600 and Sn 25 to 300 mgl^-1; and Mn 100 to 600 and Ag 25 to 100 mgl^-1). These were filter-sterilized and incorporated into malt extract agar and mycelial radial growths were recorded over 13-days. Cultural, macroscopic and microscopic morphology revealed fungal identities as Aspergillus niger, Aspergillus nidulans and Aspergillus flavus. With A. niger exposed to pb and Co, A. nidulans, Fe and Sn and A. flavus, Mn and Ag, all species exhibited no statistical difference (p>.05) to controls. Throughout the incubation period, species revealed significant (p<.05) response and growth patterns comparable to controls. Furthermore, species’ metal tolerance index (0.95-1.04) indicated high to very high tolerance. A. niger and A. nidulans demonstrated exceptional tolerance ≥1 to Co and Sn concentrations. Overall, A. niger, A. nidulans and A. flavus expressed tolerance to all test metals at elevated concentrations exceeding world permissible limits. These characteristic traits of the Aspergillus species indicate their valuable potential as mycoremediative candidates for the clean-up of heavy metal polluted environments.            

Key words: Aspergillus specie, heavy metal tolerance, mycoremediation, indiscriminate solid waste disposal, tolerance index rating.