Investigating the Effectiveness between Using Pseudomonas fluorescens and Its Biosurfactant in Bioremediation of Petroleum Hydrocarbon Contaminated Soil

Aim: To investigate the effectiveness of using Pseudomonas fluorescens and its biosurfactant in bioremediation of petroleum hydrocarbon contaminated soil.

Study Design: (1) Culturing Pseudomonas fluorescens for biosurfactant production using an optimized glycerol-mineral salt medium. (2) Separately using the biosurfactant and the bacterium to remediate hydrocarbon contaminated soil, (3) Determining the extent of hydrocarbon removal between the use of the bacterium and its biosurfactant.

Place and Duration of Study: Department of Microbiology, University of Port Harcourt, Nigeria; Between February 2017 and July 2017.

Methodology: Pseudomonas fluorescens was cultured for biosurfactant production using a glycerol-mineral salt medium with optimized parameters deciphered from a previous study. About 100 ml of the biosurfactant produced was added to petroleum hydrocarbon contaminated soil in a bioremediation setup. Also, 100 ml broth culture of the bacterium was added to hydrocarbon contaminated soil in another bioremediation setup. A control was also set up. The bioremediation and control setups were monitored for Total heterotrophic bacterial population, Hydrocarbon utilizing bacterial (HUB) population, pH, and total hydrocarbon concentration.

Results: Biosurfactant production was indicated by a reduction of the surface tension of the culture broth from 60.04 mN.m-1 to 30.64 mN.m-1. Addition of the biosurfactant to petroleum hydrocarbon contaminated soil resulted in about 69% decrease in hydrocarbon concentration. On the other hand, the addition of the bacterium resulted in about 66% decrease in hydrocarbon concentration. There was about 50% decrease in hydrocarbon concentration in the control setup. The HUB population in the bioremediation setup in which biosurfactant was added ranged from 1.70 × 104 - 4.80 × 106 cfu.g-1, while the HUB population in the setup in which the bacterium was added ranged from 2.17 × 104 - 1.35 × 106 cfu.g-1. The HUB population in the control setup ranged from 6.33 × 103 - 9.15 × 104 cfu.g-1.

Conclusion: Though the extent of hydrocarbon attenuation via the use of biosurfactant was higher than that using the bacterium, analysis of variance of the results showed that there is no significant difference between the use of the biosurfactant producing bacterium and its biosurfactant in bioremediation of petroleum hydrocarbon polluted the soil.