Surfactant Mediated Biodegradation of Aromatic Hydrocarbons Using Rhamnolipid Producing Bacterial Isolate

Abstract

Aromatic hydrocarbons (toluene and xylene) are highly water soluble and their contamination with groundwater is a serious issue. Hydrocarbons are growth substrates for microorganisms which use them as a sole source of carbon and energy. Surfactants increase the solubility and dissolution of hydrocarbons thus making them susceptible to degradation. In this study, biodegradation of toluene and xylene using a soil bacterium was evaluated in the presence of chemical surfactant. The colonies that were tested positive for xylene and toluene degradation in the primary screening were analyzed by 16s rRNA sequencing and identified as Bacillus cereus. The presence of chemical surfactant enhanced the growth of bacterial isolate and its bioremediation activity indicated the possible role of the tween in bioremediation process. It was observed that pH of the medium has reached near neutral from initial pH of 8.2 at the end of 21 days cultivation period. Addition of hydrocarbons in the mineral salt medium (MSM) has enhanced the bacterial growth as confirmed by increasing optical density throughout the cultivation period. Increase in protein content of bacterial isolate indicated its metabolic activity in the presence of hydrocarbons. Similarly, increase in the rhamnolipid concentration of B. cereus grown in MSM along with hydrocarbons and chemical surfactant indicated the role of rhamnolipids during the biodegradation of xylene and toluene.