Environmental pollution has become one of the most crucial problems of the modern society. Pyridine and its derivatives are one of the most widespread classes of heterocyclic industrial contaminants. Due to rather tough safe levels, thorough purification of the waste waters containing these ecotoxicants is required. However the existing chemical methods are not efficient. On the contrary, microbiological approach seems quite promising. A new strain degrading alkylpyridines was isolated from the soil contaminated with pyridine containing wastes. The strain was identified as Arthrobacter sp. KM-4 (VKM Ac-1098D). The strain completely consumes pyridine (2.5 g/l), 2-methylpyridine (2.5 g/l), 4-methylpyridine (1.5 g/l) and 2,6-dimethylpyridine (3 g/l) in aquatic solutions in 24 h. The intermediate products of the biodegradation process were identified using gas chromatography-mass spectrometry (GC-MS). Degradation schemes were proposed for pyridine and 2-methylpyridine. Previously unknown pathway of pyridines microbial degradation via intermediate formation of pyrrolidines was reliably proved by mass spectra and following synthesis of the identified compounds. New culture significantly surpasses all the known strains in the pyridines' degrading efficiency. Arthrobacter sp. KM-4 is a promising culture for application for the purification of waste water.

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Absrtact-The ability of Rhizoctonia solani VKM F-942 to regioselective metabolize the fluoroquinolones ofloxacin and enrofloxacin was investigated. The fungus was grown in sucrose/peptone broth at 28°C, dosed with 100 g/mL ofloxacin or enrofloxacin, and incubated with shaking for 18 days. The cultures were extracted with ethyl acetate, which was evaporated in vacuo. High-performance liquid chromatography showed that both drugs were transformed to single metabolites, which were identified by mass spectrometry and proton nuclear magnetic resonance spectrometry. The product from ofloxacin (40.0% of the total peak area at 280 nm) was ofloxacin N-oxide and the product from enrofloxacin (14.4% of the total peak area at 280 nm) was enrofloxacin N-oxide. INTRODUCTIONThe fluoroquinolones are synthetic antimicrobial agents that are active against a broad spectrum of pathogenic bacteria. Two of the widely used fluoroquinolones are ofloxacin and enrofloxacin; ofloxacin is used for treatment of various bacterial infections in humans (Monk and Campoli-Richards, 1987) but enrofloxacin is restricted to veterinary use (Brown, 1996). Both drugs are used in Japan to treat respiratory diseases of poultry (Nakamura, 1995).Ofloxacin is transformed in experimental animals to ofloxacin O-glucuronide, N-desmethyl-ofloxacin, and ofloxacin N-oxide (Sudo et al., 1986). Enrofloxacin is transformed in rats to enrofloxacin O-glucuronide and to desethyl-enrofloxacin (= ciprofloxacin) in several mammals (Heitzman, 1995;Mengozzi et al., 1996). In poultry, enrofloxacin metabolites are formed by deethylation and Nhydroxylation as well as by opening of the piperazine ring (Heitzman, 1995).Although the transformation of ofloxacin by fungi has not been reported, cultures of wooddecaying fungi have been shown to convert enrofloxacin to CO 2 and several other metabolites (Martens et al., 1996;Wetzstein et al., 1997). The fungus Mucor ramannianus transforms enrofloxacin to enrofloxacin N-oxide, desethylene-enrofloxacin, and N-acetylciprofloxacin (Parshikov et al., 2000). We now have investigated the transformation of fluoroquinolones by another fungus, Rhizoctonia solani VKM F-942. MATERIALS AND METHODSRhizoctonia solani VKM F-942 was from the AllRussian Microorganism Collection and maintained on agar slants (Modyanova et al., 1999; Khasaeva et al., 2016a,b). The mycelium was scraped from the surface of the agar, suspended in 5 mL of sterilized water, and used to inoculate 500 ml flasks. Each flask contained 100 mL of a medium containing (per liter): 30.0 g sucrose, 5.0 g peptone, 3.0 g NaCl, 3.0 g NaNO 3 , 5.0 g KH 2 PO 4 , 0.5 g MgSO 4 .7H 2 O, 0.5 g KCl, 0.1 g FeSO 4 , 1 mg MnSO 4 , and 1000 mL deionized water. The pH was adjusted to 5.0. Cultures were grown for 2 days on a rotary shaker at 28°C with shaking at 180 rpm.Ofloxacin and enrofloxacin were purchased from Sigma Chemical Co. These compounds were dissolved (at 10 mg mL -1 ) in 20 mM aqueous KOH and filter-sterilized; 1.0 mL was added to each flask to make the final concentrations 249 M ofl...

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