Biodegradation Studies of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) Compounds by &lt;i&gt;Gliocladium sp.&lt;/i&gt; and &lt;i&gt;Aspergillus terreus&lt;/i&gt;

N Usman,H.I Atta,M.B Tijjani

doi:10.4314/jasem.v24i6.19

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

Highlights

Microorganisms are able to directly degrade toxic hydrocarbons such as BTEX into less toxic compounds by consuming the available carbons within the structure of the hydrocarbons (Farhadian et al, 2008)
In view of the above, this study was aimed at using Gliocladium sp. and Aspergillus terreus isolated from soil polluted with petroleum hydrocarbons for BTEXdegradation and the objectives’ are to determine the percentage of BTEX-degradation, Hydrocarbonutilizing fungal (HUF) spores counts and statistical analysis of the mean values for amount of BTEX degraded and hydrocarbon-utilizing fungal counts using one-way analysis of variance (ANOVA)
The highest percentage BTEX degradation was observed with Aspergillus terreus (89.1%) and the least performance was observed with Gliocladium sp. (84.4%)

Summary

Introduction

Microorganisms are able to directly degrade toxic hydrocarbons such as BTEX into less toxic compounds by consuming the available carbons within the structure of the hydrocarbons (Farhadian et al, 2008). Fungi generally withstand harsher environmental conditions than bacteria and could play an important role in the degradation of petroleum hydrocarbons in the soil (Prenafeta-Boldu et al, 2002). There are two major steps involved in the biodegradation of an aromatic molecule; activation of the ring and ring cleavage (Kothari et al, 2004). The aerobic degradation of monoaromatic compounds follows different metabolic pathways based on the enzyme system present in the microorganism (Cao et al, 2009). Aspergillus terreus isolated from soil polluted with petroleum hydrocarbons for BTEXdegradation and the objectives’ are to determine the percentage of BTEX-degradation, Hydrocarbonutilizing fungal (HUF) spores counts and statistical analysis of the mean values for amount of BTEX degraded and hydrocarbon-utilizing fungal counts using one-way analysis of variance (ANOVA) In view of the above, this study was aimed at using Gliocladium sp. and Aspergillus terreus isolated from soil polluted with petroleum hydrocarbons for BTEXdegradation and the objectives’ are to determine the percentage of BTEX-degradation, Hydrocarbonutilizing fungal (HUF) spores counts and statistical analysis of the mean values for amount of BTEX degraded and hydrocarbon-utilizing fungal counts using one-way analysis of variance (ANOVA)

Objectives

Methods

Results

Conclusion