Bacterial aerobic degradation of benzene, toluene, ethylbenzene and xylene

Abstract

Several aerobic metabolic pathways for the degradation of benzene, toluene, ethylbenzene and xylene (BTEX), which are provided by two enzymic systems (dioxygenases and monooxygenases), have been identified. The monooxygenase attacks methyl or ethyl substituents of the aromatic ring, which are subsequently transformed by several oxidations to corresponding substituted pyrocatechols or phenylglyoxal, respectively. Alternatively, one oxygen atom may be first incorporated into aromatic ring while the second atom of the oxygen molecule is used for oxidation of either aromatic ring or a methyl group to corresponding pyrocatechols or protocatechuic acid, respectively. The dioxygenase attacks aromatic ring with the formation of 2-hydroxy-substituted compounds. Intermediates of the "upper" pathway are then mineralized by either ortho- or meta-ring cleavage ("lower" pathway). BTEX are relatively water-soluble and therefore they are often mineralized by indigenous microflora. Therefore, natural attenuation may be considered as a suitable way for the clean-up of BTEX contaminants from gasoline-contaminated soil and groundwater.

Degradation of monoaromatics by Bacillus pumilus MVSV3

“…Use of microorganism is considered to be the best suitable way for the clean up of BTEX contaminants from gasoline contaminated soil and water 1 . Use of bacteria and its enzyme to degrade BTEX also helps in overcoming the difficulties and constrains with other conventional chemical methods 32 .…”

“…These compounds are in the European priority lists and are found commonly as groundwater contaminant due to their extensive use in petroleum industry or as solvent 1 . They are toxic and produce significant health issues when exposed to concentrations higher than the EPA (Environment Protection Agency) maximum contaminant levels 2 .…”

Catechol biodegradation kinetics using Candida parapsilopsis

“…Wastewater from coal conversion processes, petroleum refineries, manufacture of pharmaceuticals, fertilizer and dyes contain phenolics compounds, which represent a serious ecological problem due to their widespread use, toxicity and occurrence throughout the environment (Godjevargova et al, 2000;Marek et al, 2001;Jindrová et al, 2002). Biological treatment process is generally used to degrade these substances and have usually been carried out through aerobic process.…”

Experimental Study on Micro-Biological Degradation of 1,3,5-TMB in Groundwater

“…Sterile controls, prepared by autoclaving for 15 mins at 120℃, were set to discern volatilization and adsorption losses of 1,3,5-TMB. The cultures were routinely examined by CPH-500E phase contrast microscope (Shanghai Changfang Optical instrument Co., Ltd, China) to ensure the absence of bacterial contamination [11]. Biodegradation was assessed by comparing the disappearance of 1,3,5-TMB in samples and controls over time.…”