Biodegradation of para-nitrophenol by Citricoccus nitrophenolicus strain PNP1(T) at high pH.

A gram-positive bacterium Citricoccus nitrophenolicus (strain PNP1(T), DSM 23311(T), CCUG 59571(T)) 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 PNP1(T) 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 NH(4)Cl-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 PNP1(T) suspended in NaHCO(3)/Na(2)CO(3) buffer were able to continuously degrade 200 mg L(-1) pNP over a 40 day period at pH 10.