Microbial detoxification of metalaxy in aquatic system Biodegradability of famoxadone by various microbial isolates in aquatic systems


Bioremediation is defined as the process whereby organic wastes are biologically degraded under controlled conditions to an innocuous state, or to levels below concentration limits established by regulatory authorities. In this study, four microorganisms (Pseudomonas sp. (EB1), Aspergillus niger (EB2), Cladosporium herbarum (EB4) and Penicillium sp. (EB3) were isolated from cucumber leaves previously treated with famoxadone, using an enrichment technique. These isolates were evaluated for the detoxification of famoxadone at the concentration level of 100 ?g mL–1 in an aquatic system. The effects of pH and temperature on the growth of the tested isolates were also investigated by measuring the intracellular protein and mycelial dry weight for bacterial and fungal isolates, respectively. Moreover, the toxicity of famoxadone after 28 days of treatment with the tested isolates was evaluated to confirm the removal of any toxic materials (i.e. famoxadone and its metabolites). The results showed that the optimum pH for the growth of famoxadone-degrading isolates (i.e. bacterial and fungal isolates) was pH 7. A temperature of 30°C appears to be optimal for the growth of either fungal or bacterial isolates. Isolates of Pseudomonas sp. (EB1) and Aspergillus niger (EB2), were the most effective isolates in famoxadone degradation, followed by isolates of Cladosporium herbarum (EB4) and Penicillium sp. (EB3), respectively. A slight toxicity of famoxadone against A. solani as a sensitive target was detected in the supernatant treated byPseudomonas sp. (EB1), Aspergillus niger (EB2) and Penicillium sp. (EB3) as compared with the control. The results suggest that bioremediation of famoxadone by Pseudomonas sp. (EB1), Aspergillus niger (EB2) and Penicillium sp. (EB3) is promising for the detoxification of famoxadone in aqueous media. Moreover, the tested microorganisms isolated from cucumber leaves may be able to significantly reduce the residue level of famoxadone in vegetable crops to below the maximum limit, especially under greenhouse conditions.