Tolerance of Some Soil Fungi to the Content of Deep Cycle Battery and Their Bioremediation Potential

Aims: The purpose of this study was to isolate and screen soil fungi that are able to tolerate the contents of spent deep cycle battery (inverter), and to test for their bioremediation potential.

Place and Duration of Study: Sample: Department of Microbiology, Rivers State University, between June 2019 and February 2020.

Methodology: Soil samples were collected from a mechanic village while spent inverter batteries were obtained from a waste vendor. The battery was forced open to extract its contents of the battery. Using standard microbiological techniques, fungi were enumerated and characterized. Stock solution of the battery content was prepared by dissolving the inverter battery content in sterile deionized water. This stock solution was used to carry out the screening test on the fungal isolates to ascertain the fungi that can tolerate the contents of the spent battery.

Results: Total heterotrophic fungal counts for the polluted and unpolluted soil were 6.0 x 103 cfu/g and 7.5 x 104cfu/g respectively. The fungal isolates identified from the polluted soil samples were members of the genera Rhizopus, Mucor, Aspergillus, Penicillium, and Candida, while, the isolates identified from the unpolluted soil sample includes: Candida sp, Aspergillus niger, Penicillium sp, Aspergillus fumigatus, Aspergillus flavus, Mucor sp, Yeast, Fusarium sp and Aspergillus sp. After the screening, total heterotrophic fungal counts for the soil ranged from 1.0 x 102cfu/g to 9.5 x 102cfu/g. Two fungi of the genera: Rhizopus and Mucor had the highest counts during 72 hours of incubation for the screening test. The results obtained from this study indicated that species of Aspergillus, Penicillium, and Candida were the most inhibited by the contents of the spent battery while Rhizopus and Mucor spp were more tolerant to the contents of the inverter. Rhizopus and Mucor spp were therefore, adopted in the bioremediation of soil contaminated with contents from the battery. It was observed that Rhizopus and Mucor spp in a consortium had the highest percentage of heavy metal removal (or uptake) in the following order: Cadmium (66.66%) > Lead (38.15%) > Zinc (26.83%) > Nickel (20.83).

Conclusion: These organisms can be used in the bioremediation of soil polluted with metals from spent deep cycle batteries.