Degradation of phenols by algae

Abstract

Abstract Strains of Chlorella sp., Scenedesmus obliquus and Spirulina maxima were tested for degradation of some phenolic compounds listed by U.S. EPA as priority pollutants. Toxins were dissolved in a medium (pH 7–7.2) without carbon source (except for testing Spirulina, in which case sodium bicarbonate was part of the medium at pH 9–9.2) and algae prepared by batch cultivation were added. Phenol was found to be degraded easily by all tested algae at a concentration about 1000 mg 1‐1. 2,4‐dimethylphenol was found to be converted by Chlorella (even at a concentration of about 1000 mg1‐1) to an isomer of dimethylbenzenediol that was in some cases accumulated in the medium. Depending upon biomass and toxin concentration the rate of degradation changed and an optimum of toxin concentration which induces degradation might exist. Complete degradation could be reached with biomass concentrations higher than 4 g 1‐1. 2,4‐dinitrophenol at a concentration of about 190 mg 1‐1 was degraded by Scenedesmus quickly after an adaptation period of 5 days. 2‐chlorophenol at a concentration about 200 mg 1‐1 was degraded and partly dechlorinated by Chlorella. Biodegradation of 2,4‐dichlorophenol was not proven but the condition under which algae can survive a higher concentration of toxin could be found. All algae tested have a mechanism for degradation of phenolic compounds.