ISOLATION AND CHARACTERIZATION OF PHENANTHRENE DEGRADING BACILLUS SUBTILIS FROM HYDROCARBON POLLUTED SOIL IN ZARIA, KADUNA STATE

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are pollutants that accumulate in the soil and sediments due to their insolubility in water and lack of volatility and thus require eco-friendly remedial strategies. A bacterial species isolated and characterized from hydrocarbon polluted soil was identified as Bacillus subtilis and studied for the ability to degrade phenanthrene as a sole source of carbon and energy. The optimal conditions for phenanthrene biodegradation were
determined to be 27 at a pH of 7.0. A significantly positive relationship was observed between microbial growth and the rate of phenanthrene degradation. The colour of the bacterial colonies on culture media changed to indigo on a plate with indole indicating the presence of the dioxygenase enzyme. The population density of Bacillus subtilis increased from 1.2×106 to 8.1×107cfu/ml on phenanthrene within 20 days, within the same period the percentage degradation of phenanthrene was 67.61%. The rate of degradation decreased from 5.15 mg L-1 day -1in 10 days to 4.35 mg L-1 day -1in 20 days at a degradation constant rate from 0.051K to 0.056K and the half-life was 13.58 days to 12.38 days respectively. This study revealed that a potential PAH strain was present in hydrocarbon polluted soil and can be useful in a detoxifying environment with toxic compounds effectively.