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Abstract
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Investigation
was carried out to assess the potential of some fungal species to tolerate
and grow in biomass in vitro in the presence of some heavy metals (HMs) (Pb,
Zn, Cr and Cd) from Kaduna Refinery and Petrochemical Company (KRPC)
effluent. This was done by subjecting all the fungal isolates through the
tolerant test (biomass production). The isolates were inoculated into
replicate 100 ml flask containing 50 ml of Potato Dextrose Agar (PDA) amended
with 5, 10 and 15 ppm of Pb, Zn, Cr, and Cd. Each test isolate was inoculated
into replicate flask containing the same medium without the HMs to serve as
control. All inoculated flasks were incubated aerobically at room temperature
on a rotatory shaker for 7 days. The mycelial mats were harvested by
filtering the cultures through preweighed filter paper (No.1). The filters
containing the mycelial mats were dried in an oven at 70 for 18 hours. It was
observed that most of the isolates tested tolerated and grew in the medium
containing 5 to 15 ppm of tested HMs.
Yield
of dry mycelia mats in the heavy metal supplemented medium were also
comparable to those grown in heavy metal free PDA medium. Three fungal
species- Aspergillus niger, Aspergillus flavus and Microsporum nanum isolated
from the refinery were found to be most tolerant to varying concentration of
heavy metals (Pb, Zn, Cr and Cd). A. niger is most tolerant to 5 µg/ml, 10
µg/ml, and 15 µg/ml concentration of HMs followed by M. nanum, A. flavus and
Penicillium marneffei. Aspergillus fumigatus, Chaetomium sp., Cunninghamella
bertholletiae, Trichophyton tonsurans and Nigrospora sp. were less tolerant
to the heavy metal concentrations. These three most tolerant fungal isolates
(M. nanum, A. flavus and Penicillium) may be important in treating systems
contaminated with heavy metals (HMs) because of their bioremediation
potential.
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