Benzo[a]pyrene removal by axenic- and co-cultures of some bacterial and fungal strains

Abstract

The efficiencies of several biological strategies as potential enhancers for removal of polycyclic aromatic hydrocarbons (PAHs) were evaluated by analyzing benzo[a]pyrene depletion at three different concentrations: viz. 25, 50 and 75 mg L −1. The effect of using individual cultures of different fungal or bacterial strains and combinations of the two to obtain defined fungal–bacterial co-cultures on benzo[a]pyrene removal was evaluated. The microbial test strains included Aspergillus niger, Penicillium Trichoderma harzianum, Saccharomyces cerevisiae, Serratia marcescens, Bacillus mycoides and Pseudomonas sp. Depletion profiles under various treatment conditions ranged from 9 to 84% and from 1 to 35% for fungal and bacterial cultures, respectively. The highest removal rate in all the treatments was achieved consistently by the fungal strains, and in general, pure cultures of both bacteria and fungi were found to be more sensitive to variations in benzo[a]pyrene concentration. When different defined fungal–bacterial co-cultures were tested, benzo[a]pyrene removal was higher (65%, 50 mg L −1) with the Penicillium sp./ S. marcescens co-culture. Our results show that the use of fungal cultures was more effective for benzo[a]pyrene degradation than the use of bacterial cultures even when the concentration was increased three-fold. Moreover, it shows that the use of a defined fungal–bacterial co-culture can enhance benzo[a]pyrene biodegradation.