Molecular characterization and lead (Pb) tolerance of Penicillium and Aspergillus species from contaminated soils in Owino Uhuru, Mombasa, Kenya

Environmental pollution, particularly from toxic organic compounds and metals such as lead (Pb), poses significant risks to human health. This study aimed to investigate Pb contamination in soil samples from the Owino Uhuru slums, Mombasa County, following the closure of a Pb-acid smelter, and to examine the Pb tolerance and bioaccumulation abilities of fungi isolated from these soils. Forty-four fungal isolates were subjected to molecular identification through analysis of their internal transcribed spacer (ITS) gene region. The identified fungal isolates belonged to the phylum Ascomycota, with Penicillium (52.3%) and Aspergillus (47.7%) as dominant genera. To assess bioremediation potential, Pb uptake was measured using Atomic Absorption Spectroscopy (AAS) by comparing initial and final Pb concentrations. Fungal isolates were cultured on Potato Dextrose Agar (PDA) plates with Pb concentrations ranging from 1.0 ppm to 0.2 ppm and incubated at 25ºC for five days. Results showed that 20.5% of the isolates exhibited significant Pb tolerance (P<0.05), with minimum inhibitory concentrations (MIC) ranging from 0.39 to 0.76 ppm. The lowest Pb concentration (0.2 ppm) resulted in the highest removal rates: Penicillium chrysogenum (94.6%) and Aspergillus niger (89.9%). Additionally, P. chrysogenum and Aspergillus welwitchae accumulated Pb up to 0.76 and 0.61 μg/mL, respectively. These findings highlight the potential of fungal species in Pb bioremediation, demonstrating their ability to absorb Pb from contaminated environments.