Biodegradation of para-nitrophenol by Citricoccus nitrophenolicus strain PNP1T at high pH
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A gram-positive bacterium Citricoccus nitrophenolicus (strain PNP1T, DSM 23311T, CCUG 59571T) isolated from a waste water treatment plant was capable of effectively degrading p-nitrophenol (pNP) as a source of carbon, nitrogen and energy for growth. Degradation of pNP required oxygen and resulted in the stoichiometric release of nitrite. Strain PNP1T also degraded 4-chlorophenol, phenol and salicylate. pNP was degraded at pH values between 6.8 and 10.0 and at temperatures between 15–32 °C. pNP at concentrations up to 150 mg L−1 were degraded during growth in media at pH ≤ 10, whereas 200 mg L−1 was completely inhibitory to growth. When incubated in an NH4Cl-free medium (pH 10) containing both pNP and acetate, pNP is degraded with concomitant release of nitrite which was subsequently assimilated during acetate degradation. Intact cells of strain PNP1T suspended in NaHCO3/Na2CO3 buffer were able to continuously degrade 200 mg L−1 pNP over a 40 day period at pH 10.
Keywordsp-Nitrophenol Biodegradation Citricoccus nitrophenolicus
The research was supported by a joint grant from Cheminova A/S, Central Denmark Region and The Aarhus University Research Foundation (AUFF). Thanks are due to Bo Breinbjerg from Cheminova A/S for HPLC measurements of pNP, to Tove Wiegers and Marco Zanella for excellent technical assistance and to Rodney A. Herbert for constructive criticism of this manuscript.
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