title: Variation in toxicity during the biodegradation of various heterocyclic and homocyclic aromatic hydrocarbons in single and multi-substrate systems.
abstract: In the present study, an attempt was made to understand the variation in the toxicity during the biodegradation of aromatic hydrocarbons in single and multi-substrate system. The bacterial bioassay based on the inhibition of dehydrogenase enzyme activity of two different bacterial sp. E.coli and Pseudomonas fluorescens was used for toxicity assessment. Amongst the chosen pollutants, the highest acute toxicity was observed for benzothiophene followed by benzofuran having EC50value of 16.60mg/L and 19.30mg/L respectively. Maximum residual toxicity of 30.8% was observed at the end during the degradation of benzothiophene. Due to the accumulation of transitory metabolites in both single and multisubstrate systems, reduction in toxicity was not proportional to the decrease in pollutant concentration. In multi-substrate system involving mixture of heterocyclic hydrocarbons, maximum residual toxicity of 39.5% was observed at the end of biodegradation. Enhanced degradation of benzofuran, benzothiophene and their metabolic intermediates were observed in the presence of naphthalene resulting in significant reduction in residual toxicity. 2 (1H) - quinolinone, an intermediate metabolite of quinoline was observed having significant eco-toxicity amongst all other intermediates investigated.
authors: Environmental and Water Resources Engineering Division, Department of Civil Engineering, IIT Madras, Chennai 600 036, India.
authors: Akashdeep Singh
authors: AS
authors: Oberoi
authors: Environmental and Water Resources Engineering Division, Department of Civil Engineering, IIT Madras, Chennai 600 036, India. Electronic address: ligy@iitm.ac.in.
authors: Ligy
authors: L
authors: Philip
mesh_terms: D001572:Benzofurans / Q000633:toxicity; D001673:Biodegradation, Environmental; D045247:Chryseobacterium / Q000187:drug effects; D004785:Environmental Pollutants / Q000633:toxicity*; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology; D006841:Hydrocarbons, Aromatic / Q000633:toxicity*; D009281:Naphthalenes / Q000633:toxicity; D010088:Oxidoreductases / Q000187:drug effects; D011551:Pseudomonas fluorescens / Q000187:drug effects / Q000201:enzymology; D015363:Quinolones / Q000633:toxicity; D013876:Thiophenes / Q000633:toxicity
chemical_list: D001572:Benzofurans; D004785:Environmental Pollutants; D006841:Hydrocarbons, Aromatic; D009281:Naphthalenes; D015363:Quinolones; D013876:Thiophenes; C088015:benzothiophene; C031721:naphthalene; D010088:Oxidoreductases; C105430:benzofuran
keywords: Acute toxicity; Biodegradation; Heterocyclic hydrocarbons; Homocyclic aromatic hydrocarbons; Metabolic intermediates