Transformation of Sulfadimethoxine In Soil Mediated by Laccase and Horseradish Peroxidase.

Soil contamination by pharmaceuticals of both human and veterinary use is an emerging problem. Application of manure into agricultural lands is one of the major route through which veterinary antibiotics enter the environment. Sulfadimethoxine is a commonly used antibiotic which is largely released into the environment from concentrated animal feeding operations (CAFO-s). Transformation of antibiotics in soil impact the likelihood of their entry to water bodies, uptake by plants, and thus their effect on terrestrial and aquatic organisms. Despite large number of studies related to the occurrence of sulfadimethoxine in the aquatic environment, there are few studies on the environmental transformation of this antibiotic in soil. Previous studies show that extracellular enzymes are capable of transforming persistent chemicals into non-harmful products, indicating that enzymes produced by microorganisms or plants may play an important role in humification, and thus removal of antibiotics. We performed experiments to examine the transformation of sulfadimethoxine in a well characterized sandy loam soil, poultry litter, or their mixture in the absence and presence of horseradish peroxidase or laccase at different levels. Significant removal of sulfadimethoxine was observed in samples with enzyme present in comparison to samples to which enzymes were not applied. Attempts were made to identify the products and elucidate the reaction pathways. This study serves as a precursor for potential development of an efficient and eco-friendly method to remediate antibiotics in soil thus restricting their movement to water bodies.