Biosorption of heavy metal polluted soil using bacteria and fungi isolated from soil

Abstract

Heavy metals polluted soils have turned out to be a common environmental problem across the globe due to their toxic effects and accumulation through the food chain. Heavy metals have lethal effects on all forms of life. For instance, plants grown on heavy metal polluted soil show a reduction in growth and yields. A surge in anthropogenic activities and industrial operations has substantially increased the level of heavy metal pollution and release into the environment; hence, there is need to remediate these heavy metal pollutants. Biosorption is an efficient, economical, ecofriendly and convenient techniques of remediating heavy metal polluted soils. It is a widely accepted method that utilizes biomaterials such as natural biomass as biosorbents. The current study was based on the biosorption of copper, chromium, cadmium and nickel polluted soil using bacteria and fungi isolated from soil. Bacterial species isolated were Pseudomonas, Bacillus, Micrococcus, Escherichia, Streptococcus, Enterobacter and Staphylococcus while fungi isolated were Aspergillus niger, Penicillium notatum and Aspergillus flavus. The isolated bacteria were screened for potential to biosorb copper and chromium likewise fungi for cadmium and nickel. Biosorption rate was determined using atomic absorption spectrophotometry. Five milliliters each of a-day-old culture of the screened bacteria and fungi was inoculated into 45 ml of nutrient broth (bacteria) and potato dextrose broth (fungi) having concentrations of 5, 10, 15 and 20 ppm, respectively, of copper, chromium, cadmium and nickel. The conical flasks were incubated at a temperature of 37 °C and 28 °C ± 2 for bacteria and fungi, respectively, for a period of 35 days of inoculation. For the bacterial isolates, the highest biosorption rates of chromium (89.67%) and copper (90.89%) by Pseudomonas aeruginosa were observed at 20 ppm on day 21 and 15 ppm on day 14, respectively, while for the fungi isolates, P. notatum showed highest biosorption rate for cadmium at 10 ppm with 77.67%. Aspergillus niger showed highest biosorption rate for nickel with 81.07% after 28 days of incubation. The results of this study revealed the ability of Pseudomonas aeruginosa to biosorb copper and chromium and also A. niger and P. notatum to biosorb cadmium and nickel from the environment and can be developed for the biosorption of soils polluted with copper, chromium, cadmium and nickel.