Biotechnology Letters 26: 681–686, 2004. © 2004 Kluwer Academic Publishers. Printed in the Netherlands. 681 Tributyl phosphate degradation by Serratia odorifera C´ ecile Berne, Blandine Montjarret, Yasmina Guountti & Daniel Garcia ∗ CEA Cadarache, DSV DEVM LBC, Univ–Méditerranée CEA 1000, F-13108 Saint-Paul-lez-Durance Cedex, France ∗ Author for correspondence (Fax: +33 4 42 25 47 01; E-mail: dgarcia@cea.fr) Received 19 January 2004; Revisions requested 2 February 2004; Revisions received 23 February 2004; Accepted 24 February 2004 Key words: degradation, Serratia odorifera, soil bacteria, tributyl phosphate, xenobiotic Abstract Several strains from tributyl phosphate (TBP)-polluted soils were isolated and screened for their ability to degraded this widely used organophosphorus compound. The most active strain, identified as Serratia odorifera, degrades up to 600 μM TBP (initially present in the medium at 2 mM) during its growth phase, within 8 h from inoculation. However, this bacterium could not utilize TBP as the sole carbon and/or phosphorus source but nevertheless is a good candidate for bioremediation of TBP-polluted industrial sites. Introduction Biodegradation of organophosphorus compounds is an important goal for the preservation of public health and the environment since these chemicals are widely used as pesticides, industrial additives and chemical warfare agents (Raushel 2002). Most of these com- pounds can be inactivated or degraded by microor- ganisms (Kumar et al. 1996). Among them, tributyl phosphate (TBP) has been poorly studied because of its low toxicity in mammals: TBP injected into rats causes no major trouble and is mainly eliminated in the urine and faeces as hydroxylated metabolites (Sa- saki et al. 1984). Nevertheless, its wide utilisation, e.g. in defoamers, plasticizers, herbicides, hydraulic fluids and as a solvent for conventional nuclear fuel processing, generates large amounts of wastes. This compound is very stable in the natural environment (soil and water) and is hardly affected by natural photolysis and hydrolysis (Environmental Protection Agency 1992). Furthermore, in spite of its low sol- ubility in water (4 mM at 30 ◦ C), TBP presents an acute toxicity hazard to freshwater living organisms, even at low concentrations (2 to 40 μM), (EPA 1992, Nakamura 1991). TBP can be degraded by mixed cultures of bacteria (Thomas & Macaskie 1998) or by bacterial isolates (Owen et al. 1992, Rosenberg & Alexander 1979, Stoner & Tien 1995, Thomas et al. 1997a, b, Thomas & Macaskie 1996). However, in the above studies, the ability to degrade TBP by isolated bacteria was rather poor or unstable during subcultures, precluding invest- igation of the enzymatic mechanisms responsible for TBP elimination from the medium. In this study, we report the isolation of a bacterium that can readily de- grades TBP in a reproducible manner and describe its behaviour during the degradation. Materials and methods Media The media used were the Tryptic soy broth medium (Sigma-Aldrich), diluted to 1/10 (Tsb) and a min- imal medium (CaCl 2 0.25 mM; MgSO 4 , 7H 2 O1mM; (NH 4 ) 2 SO 4 0.5 mM; KCl 1 mM; NaCl 1.5 mM; Na 2 - EDTA 0.04 mM; MOPS 25 mM; ZnSO 4 25 nM; MnCl 2 10 nM; FeSO 4 , 7H 2 O5nM; CoCl 2 2nM; CuSO 4 , 5H 2 O2nM; NaMoO 4 , 2H 2 O2nM; pH 7). When re- quired, glucose (1 mM) was used as the carbon source in the minimal medium and phosphate buffer (50 mM, pH 7) as the phosphorus source. Experiments were performed under both liquid and solid conditions. In the latter case, the liquid medium was supplemented