Effect of Light on the Biodegradation of Crude Oil by the Algae Closterium species

Abstract

Effect of light on the ability of algal isolates to degrade crude oil was studied using standard methods. Identification tests revealed isolates of Closterium sp which was used in this study. Total viable counts were evaluated, which showed an increase from 6.0 x 10⁴ to 3.2 x 10⁶ cfu/mL in 21days in the presence of light and from 6.0 x10⁴ cfu/mL to 3.56 x 10⁶ cfu/mL in the dark phase. Optical densities (OD) at 520nm also increased from 0.160 to 0.500 in 21days in the presence of light and from 0.160 to 0.805 in 21days in the absence of sunlight. The gas chromatographic analysis showed a decrease in total petroleum hydrocarbon (TPH) from 12,405 to 1,470mg/L in 21days in the presence of sunlight and from 12,405 to 144mg/L in 21 days in the dark. Algae possess a greater ability to degrade crude oil in the absence of sunlight than in the presence of sunlight. We suggest that Closterium sp can potentially bioremediate the crude oil-polluted environment, particularly in the dark.

Keywords: Biodegradation, algae, total petroleum hydrocarbon, Closterium sp, gas chromatography