Biodegradation Studies of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) Compounds by <i>Gliocladium sp.</i> and <i>Aspergillus terreus</i>

Abstract

Benzene, toluene, ethylbenzene and xylene (BTEX) are monoaromatic hydrocarbons found frequently in petroleum and its derivatives; and they are among the most important pollutants of soil and groundwater. This study focused on harnessing the enzymatic capabilities of filamentous fungi Gliocladium sp. and Aspergillus terreus, dwelling in a petroleum-contaminated soil to degrade benzene, toluene, ethylbenzene and xylene (BTEX) compounds. The biodegradation experiment was carried out using the fungi individually and in consortium in a batch culture containing mineral salts medium supplemented with 1% v/v BTEX. The experiments were carried out in triplicates at room temperature on a rotary shaker (180rpm) for twenty five days and aliquots were taken on a five day interval to determine the hydrocarbon utilizing fungal (HUF) count and residual BTEX in order to monitor the rate of biodegradation. The hydrocarbon utilizing fungal counts were determined by direct counting using a Neubauer  Haemocytometer while, the residual BTEX was determined using absorbance values measured using a spectrophotometer and the corresponding concentrations determined from a standard curve. The highest percentage degradation of BTEX was observed with Aspergillus terreus (89.1%) while, the least was observed with Gliocladium sp. (84.4%). The growth peak was attained on the 15th day in all treatments after which the HUF counts declined. Statistical analysis showed no significant difference (P>0.05) in the mean amounts of BTEX degraded and hydrocarbon-utilizing fungal counts between the treatments. The strains of Gliocladium sp. and Aspergillus terreus used in this study showed high ability for BTEX degradation thus, they are potential candidates for bioremediation of soils contaminated with monoaromatic hydrocarbons.

Keywords: Biodegradation, BTEX, Gliocladium sp., Aspergillus terreus, Monoaromatic hydrocarbons