Extracellular Polymeric Substances from a Fungus Are More Effective than Those from a Bacterium in Polycyclic Aromatic Hydrocarbon Biodegradation

Abstract

To investigate the differential contribution of extracellular polymeric substances (EPS) to polycyclic aromatic hydrocarbon (PAH) degradation by fungi and bacteria, the PAH-degrading ability and characteristics of EPS from the bacterium Mycobacterium gilvum SN12 and the fungus Mucor mucedo were compared. The fungus degraded 11% more pyrene and 21% more benzo[a]pyrene (B[a]P) than the bacterium. The biodegradation of pyrene and B[a]P increased after EPS were introduced into the PAH degradation solution, and 5.0% more pyrene and 4.5% more B[a]P were achieved for the added EPS from the fungal compared with the bacterial isolate. The comparison of two EPS indicated that the amount of protein and carbohydrate in EPS from the fungus was greater than that from the bacterium and was especially enriched for tryptophan, which is positively related to the increase of PAH biodegradation by fungal EPS. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) further revealed that higher molecular weight (HMW) of proteins over 200 kDa only existed in EPS from the fungus, and the polymorphism of proteins in EPS from the fungus was more abundant than that from the bacterium. The HMW proteins with stronger hydrophobicity in the fungal EPS also enabled the fungus to absorb more PAH than the bacterium. The results demonstrated that the pronounced differences in the characteristics of EPS from the fungal and the bacterial sources are responsible for the differential effects on PAH biodegradation.