Q-191. Comparison of Benzo[a]Pyrene Degradation by Bacterial and Fungal Cultures in Liquid Medium

C. Machín-Ramírez1,2, D. Morales-Guzmán1, K. P. Mayolo-Deloisa2, F. Martínez-Morales1, M. Trejo-Hernández1;
1Ctr. de Investigación en Biotecnología. Univ. Autónoma del Estado de Morelos, Cuernavaca Morelos, MEXICO, 2Facultad de Ciencias Químicas e Ingeniería, Cuernavaca Morelos, MEXICO.

Polycyclic aromatic hydrocarbons (PAHs) are priority pollutants due to their potential toxicity, mutagenicity, and carcinogenicity. Recalcitrance of PAHs to microbial degradation has led to research focused on evaluating a wide phylogenetic spectrum of microorganisms for their degradative ability. In this context, seven fungal and bacterial strains isolated from an aged and heavily contaminated sludge waste (PB401) in Mexico (southestern) were screened to assess their benzo[a]pyrene degradative potential. Microbial strains tested were:Aspergillus niger, Penicillium sp., Trichoderma sp., Saccharomyces cerevisiae, Serratia marcescens, Bacillus mycoides, and Pseudomonas sp. Microbial degradation of benzo[a]pyrene was studied at 25, 50 and 75 mgL-1 in liquid medium (YE, 20 ml). Incubations were carried out under aerobic conditions at 20°C for 5 days at 175 rpm. Solvent extracts of the fermentation broth and mycelium (for fungal treatments) were analyzed by gas chromatography at initial and final time. Microbial growth was measured by viable cell count and dry weight. During screening, we found that all bacteria and fungal strains isolated could use benzo[a]pyrene as their sole carbon source in a basal salt medium (BSM). No abiotic losses were detected during incubations. Benzo[a]pyrene degradation percentages under the various treatment conditions ranged between 9 and 84 % and between 1 and 35% for fungal and bacterial cultures respectively. For the three systems used, we found that highest benzo[a]pyrene removal was achieved always by fungal strains. Nevertheless, degradation was found to be more sensitive to benzo[a]pyrene concentration variations for both, bacterial and fungal cultures. At 25 mgL-1 , Highest removal resulted by Penicillium sp. (84 %) and Trichoderma sp. (77%) (There was no significant difference in the extent of biodegradation). When benzo[a]pyrene concentration was 75 mgL-1, removal achieved by Penicillium sp. was 50%. Our results shows that use of fungal cultures was more effective for benzo[a]pyrene degradation than the use of bacterial cultures, even when benzo[a]pyrene concentration was increased three-fold.