Biodegradation of Nonylphenol by Rhizospheres of Spirodela polyrrhiza

Isolation and Characterization of Nonylphenol-degrading Bacteria Isolated from the Rhizosphere

Abstract

Degradation experiments of nonylphenol (NP) in pond water samples were performed with and without the giant duckweed, Spirodela polyrrhiza. The results revealed that NP was efficiently biodegraded and removed only when S. polyrrhiza, which was enriched with NP-degrading rhizobacteria, was planted. Two strains of NP-degrading bacteria, designated strains ISNP-A and -B, were isolated from the S. polyrrhiza rhizosphere. These isolates exhibited a higher NP-degrading ability than those previously isolated from the natural environment. However, the isolates lost their NP-degrading ability with repeated cultivation. Therefore, it is suggested that a rhizosphere environment is indispensable to ensure the NP-degrading ability of rhizobacteria.