Biodegradation of Phenolic Pollutants

Abstract

Phenolic compounds are important constituents of petrochemical waste waters arising from transformation processes. Phenol together with substituted halophenols, nitrophenols and alkyl phenols are the main constituents. An Arthrobacter citreus spp. strain MSA - 2005 initially selected for growth at the expense of phenol as the sole source of carbon and energy, was enriched with phenolic    compounds    such    as    4-nitrophenol,    4- chlorophenol and 4-methyl phenol. Metabolization of these compounds upto their maximum levels in the mineral salt medium was studied. The complete metabolization    of 4-nitrophenol    upto    15mM,    4- chlorophenol up to 12mM and 4-methyl phenol upto 6mM against phenol upto 22mM was achieved in 24 hours. The metabolism of these compounds by the isolated strain occurred through the involvement of catechol derivatives as key intermediates which are further hydrolysed to hydroxy quinol which enters the β -keto adipate pathway. Results indicate that the cells contain mono and di- oxygenase enzymes necessary for these conversions. The degradation rates of these phenolic compounds, by agar immobilized cells has also been reported.