International Biodeterioration & Biodegradation 60 (2007) 226–230 Microbial degradation and detoxification of 2,4-dinitrophenol in aerobic and anoxic processes $ Virginia L. Gemini a,Ã , Alfredo Gallego a , Valeria Tripodi b , Daniel Corach b , Estela I. Planes c , Sonia E. Korol a a Chair of Hygiene, Faculty of Pharmacy and Biochemistry, University of Buenos Aires, Junı´n 956, (1113) Buenos Aires, Argentina b Digital Genetic Fingerprinting Service, Faculty of Pharmacy and Biochemistry, University of Buenos Aires, Junı´n 956, (1113) Buenos Aires, Argentina c National Institute of Industrial Technology, Av. General Paz 5445, C.C. 157, (1650) San Martı´n, Buenos Aires, Argentina Received 6 November 2006; received in revised form 20 March 2007; accepted 24 March 2007 Available online 11 May 2007 Abstract A bacterial strain was isolated from a river sediment in Buenos Aires, Argentina, owing to its ability to utilize 2,4-dinitrophenol (2,4-DNP) as the sole carbon, nitrogen and energy source. The strain was identified as Rhodococcus opacus on the basis of its 16S rRNA gene sequence. R. opacus degrades aerobically 0.27 and 0.54 mM within 22 and 28 h, respectively, and releases the nitro groups from 2,4- DNP as nitrites. Aerobic biodegradation processes were performed using a 2-l volume microfermentor at 28  C with agitation (200 rpm), and were evaluated by spectrophotometry, high performance liquid chromatography (HPLC) and microbial growth. The absence of 2,4- DNP transformation products was also confirmed by gas chromatography mass spectrometry (GC–MS). As the nitrite released during 2,4-DNP degradation is in addition an environmental toxic agent it was removed by denitrification in an anoxic process. Detoxification was assessed by using luminescent bacteria, algae and seeds toxicity tests. Toxicity was not detected after combining both the aerobic and anoxic processes. r 2007 Elsevier Ltd. All rights reserved. Keywords: 2,4-Dinitrophenol; Biodegradation; Detoxification; Aerobic process; Anoxic process 1. Introduction Nitrophenols are among the most widely used industrial organic compounds. They are frequently used as inter- mediates in the manufacture of pharmaceuticals, dyes, pesticides and explosives (Spain, 1995; Zablotowicz et al., 1999; She et al., 2005). Because of their widespread use nitrophenols are therefore found as contaminants in industrial effluents, rivers, groundwater and pesticide- treated soils (Lenke et al., 1992; Marvin-Sikkema and de Bont, 1994). Like most nitrophenols, 2,4-dinitrophenol (2,4-DNP) is highly toxic to living organisms. The U.S. Environmental Protection Agency (EPA, 1980) has listed 2,4-DNP as ‘‘priority pollutant’’ and recommends restrict- ing its concentrations in natural waters to below 0:01 mgl 1 . In Argentina effluents containing 2,4-DNP are often discharged into streams untreated or only slightly treated. Concentration data available for industrial waste- water are generally expressed in terms of total concentra- tion of phenols in several countries (Tomei et al., 2006). As regards Argentine legislation, it sets a limit of o500 m l 1 for effluents discharged into surface water (Resolution 336, 2003). Even though the resistance to biodegradation of the aromatic ring is enhanced by the nitro groups of 2,4-DNP, a number of bacterial strains have been reported which are capable of using 2,4-DNP as their sole carbon and nitrogen source (Hess et al., 1990; Lenke et al., 1992; Blasco et al., 1999; Ebert et al., 1999). Among these bacteria, some Rhodococcus strains exhibit high potential for the degrada- tion of the compound. However, despite the availability of information on 2,4-DNP biodegradation, there is lack of ARTICLE IN PRESS www.elsevier.com/locate/ibiod 0964-8305/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ibiod.2007.03.006 $ This paper is scientifically relevant because it widens the scope of the use of indigenous strains to biodegrade and detoxify pollutants. Here, we focus on a strain which solves the problem of 2,4-DNP a common environmental pollutant in Argentina. Ã Corresponding author. Tel.: +54 11 4964 8258. E-mail address: vgemini@ffyb.uba.ar (V.L. Gemini).