Efficient biodegradation of malachite green by a newly isolated Klebsiella pneumoniae strain WA-1

Biodegradation by microorganisms is a potential treatment technique of malachite green (MG) in aquaculture environments. In this study, a bacterium with high MG decolorization and biodegradation ability was isolated through enrichment culture and color-decoloration circle method, and was identified as Klebsiella pneumoniae WA-1 after molecular and biochemical identification. The MG biodegradation characteristics and the factors affecting the MG biodegradation ability of this strain were studied using KBH4 reduction-high performance liquid chromatography with fluorescence detector (HPLC-FLD) method. K. pneumoniae WA-1 could efficiently biodegrade MG in aqueous solution without any nutrients that over 94.0% MG was biodegraded by this strain at 1-20 mg/L within 0.5 hr and 100% MG were biodegraded at 1-10 mg/L within 12 hr. Fairly stable MG biodegradation performance was observed in complex environments, including various pH, temperature, salinity, and metal ions, especially at low MG concentration. Furthermore, the presence of NaCl, Mn2+, Mg2+, or Cu2+ could enhance the MG biodegradation ability of this strain. These results indicate that K. pneumoniae WA-1 could be used as a potential MG degradation agent in complex aquaculture environments.