Bioaccumulation of lead (Pb), chromium (Cr) and cadmium (Cd) by Aspergillus flavus and Fusarium oxysporum isolated from tannery wastewater

Fifty (50) fungal isolates were isolated from tannery wastewater from our previous experiment of which Aspergillus flavus and Fusarium oxysporum were the most dominant and least fungal species identified. The concentration of the three heavy metals in the tannery wastewater and mycelia of the two fungal isolates were determined before and after the remediation studies. This was done by digesting 1.0g of the fungal mycelia tissue of each of the isolates using 17.5 ml of concentrated nitric acid (HNO3) and 12.5 ml of concentrated hydrochloric acid (HCl). This was followed by subsequent heating to dryness and making up the volume of the digest to 50 ml using sterile distilled water. The digest was then filtered to remove insoluble material that could clog the atomizer and the filtrates were then analyzed for Pb, Cr and Cd using atomic absorption spectrophotometer. The growths of the tested fungi were monitored in Potato dextrose broth (PDB) medium amended with untreated tannery wastewater in the ratio 1:3 for a period of one week (7 days). The heavy metal uptake and removal capacity of the test fungi was calculated according to standard procedures. With respect to Pb, Cr and Cd, maximum uptake of 42.00, 88.00 and 29.00 mg/g was observed for F. oxysporum , while 36.00, 23.46 and 1.09 mg/g was observed for A. flavus respectively. Both fungal isolates were further characterized using molecular approach to confirm their identity. Therefore, it was concluded that these identified fungi have the potential as bio-sorbent for the remediation of sites contaminated with Pb, Cr and Cd respectively