Kalaichelvan, G:Anaerobic bioconversion of aromatic compounds

Kalaichelvan, G, Anaerobic bioconversion of aromatic compounds, (Ed.) S.Jisha, B.Hari & T.K.Remesan, Proc. Nat. Sem. on Env. Biotech. Chall. and Oppor.,  ENVIROTECH-2008, P.G. Dept. of Zoology, S.N.C. Natiika, pp 27

(School of Biotechnology, Chemical and Biomedical Engineering, Vellore Institute of Technology, Vellore, e.mail: gkalaichelvan@vit.ac.in)

Abstract

Aromatic compounds are major constituents of natural and synthetic chemicals. Many compounds are considered recalcitrant since not many organisms are able to use them for their metabolic needs. Even those organisms which use them, prefer a co-metabolism or secondary metabolism. Majority of the decomposition of these aromatic compounds occur through aerobic pathways by which the C present is oxidized to carbon di-oxide. Many fungi and some bacteria and actinomycetes are involved in this bioconversion. In nature, many habitats such ocean sediments, river estuaries, effluent lagoons, deep soil lack sufficient oxygen but still bioconversion of the phenols take place. Many anaerobic and facultative anaerobic bacteria are involved in these processes which differ metabolically from aerobic metabolism. A reductive cleavage and hydrolytic attack is postulated as opposed to the oxygenolysis in aerobic paths. In place of oxygen, other electron acceptors like sulphate, nitrate, format etc., function as electron acceptors. After ring opening, these compounds enter into metabolism via β-oxidation.  The main application of the organisms is in treating phenol containing wastewaters, distillery and paper factory effluent treatments and in situ bioremediation. Many toxic contaminants like chlorobenzenes, nitro-phenols have been transformed under anaerobic conditions. A role for the enzymes of anaerobic aromatic bioconversion is envisaged in semi-organic synthesis and biotranformation reactions.