ASSESSMENT OF THE POTENTIAL OF FUNGAL SPECIES IN THE BIOACCUMULATION OF LEAD, NICKEL AND CADMIUM FROM REFINERY EFFLUENT

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Date
2015-04
Authors
EZEONUEGBU, Blessing Amaka
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Abstract
This study was carried out to assess the potential of fungal species in the bioaccumulation of lead, nickel and cadmium by fungal species isolated from refinery effluent and effluent impacted River. Physicochemical, heavy metal and mycological analyses were carried out on untreated and treated effluent from Kaduna Refinery and Petrochemical Company (KRPC) and water samples from Romi River, Kaduna State, Nigeria, using standard procedures. A total of 133 fungal isolates belonging to 15 species (Aspergillus flavus, A. niger, A. fumigatus, A. carbonarius, A. glaucus, Penicillium spp., Fusarium spp., Curvularia spp., Trichodermaspp., Nigrosporaspp., Microsporum spp., Rhizoctonia spp., Trichophytonspp., Geotrichum spp.and Chaetophoma spp.) were isolated from the study site, identified and characterized on the basis of their macroscopic and microscopic morphologies using standard taxonomic guides. Aspergillus flavus had the highest percentage occurrence of 18.05% followed by Penicillium spp. and Curvularia spp. which had equal occurrence of 12.78% each. A. glaucus and Trychophytonspp. had the least and equal percentage occurrence of 0.75% each. The isolates were inoculated into duplicate 100ml flask containing 50ml of potato dextrose broth (PDB) supplemented with 5,10 and 15µg/ml of Pb, Ni, and Cd analytical grade salts. Each test isolate was inoculated into duplicate flask containing the same medium without the heavy metals to serve as control. All inoculated flasks were incubated aerobically at room temperature on a rotator shaker for 7days. The mycelial mats were harvested by filtering the cultures through pre weighed filter paper (No.1). The filters bearing the mycelial mats were dried in an oven at 70oC for 18hours and weighed. Yields of dry mycelial mats in the heavy metal supplemented medium were also comparable to those grown in heavy metal free PDB medium. It was observed that 52 out of the 133 fungal isolates tested, resisted and grew in the medium containing 5, vii 10 and 15ppm of the test heavy metals. pH and temperature optimization studies on growth conditions of the resistant isolates were carried out at varying pH of 4, 5, 6 and 7 and varying temperatures of 25oC, 30oC and 35oC. The various test isolates grew optimally at the varying pH and temperature levels except pH 7 and temperature of 35oC. Heavy metal uptake capacity and removal from refinery effluent by the test fungal isolates were also determined. The genera Aspergillus, Penicillium, Trichoderma, Curvularia, Fusarium and Nigrosporaaccumulated and removed substantial amount of Pb, Ni and Cd from the effluent. Trichoderma sp. and Microsporumsp. had an uptake capacity of 0.28mg/g of lead each. Nigrosporasp. and Fusarium sp. had an uptake capacity of 0.14mg/g and 0.13mg/g of nickel respectively. The uptake capacity of cadmium by Penicillium sp. was 0.02mg/g while A. flavusand A. niger removed 71.29% each of lead. A. nigerwas able toremove 85.06% of nickel while 85% of cadmium was removed by Penicillium sp. It was therefore concluded that, fungi constitute a significant proportion of the microflora of sites contaminated with the refinery effluent and could be playing an important role in the remediation of sites receiving the effluent. Also, their tolerance to Pb, Ni and Cd indicates that these test fungal isolates, could be employed in the treatment of refinery effluents and bioremediation of water bodies and sites polluted with Pb, Ni and Cd.
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A THESIS SUBMITTED TOTHE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIALFULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OFMASTER OF SCIENCE DEGREE IN MICROBIOLOGY DEPARTMENT OF MICROBIOLOGY FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY, ZARIA NIGERIA
Keywords
FUNGAL SPECIES,, BIOACCUMULATION,, LEAD,, NICKEL,, CADMIUM,, REFINERY EFFLUENT
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