Phenol and catechol biodegradation by the haloalkaliphile Halomonas campisalis: influence of pH and salinity

Abstract

Removal of aromatic compounds from alkaline and/or saline industrial wastewater is an environmental concern for industry. In addition, aromatics may be accumulating in soda lakes, unique natural systems, where the fate and toxicity of these contaminants is unknown. To determine the feasibility of aromatic compound biodegradation in saline and alkaline conditions, the effect of pH and salinity on the biodegradation of phenol as a model aromatic waste compound by the haloalkaliphilic bacterium Halomonas campisalis was examined. Phenol was degraded as a source of carbon and energy at pH 8-11 and 0-150 g/L NaCl. Metabolic intermediates catechol, cis,cis-muconate, and (+)-muconolactone were identified, thus indicating that phenol was degraded via the beta-ketoadipate metabolic pathway. Although phenol and catechol were completely degraded in all cases, small amounts of cis,cis-muconate accumulated proportionally to increases in pH. There was no noticeable influence of salinity on cis,cis-muconate accumulation except at 0 g/L NaCl where it was completely degraded. These results indicate that it may be feasible to use haloalkaliphiles forthe treatment of aromatics present in saline and/or alkaline systems. This is the first report of phenol and catechol biodegradation under combined saline and alkaline conditions.