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Biomedical subjects

F Lépine

Publications and source records attributed to F Lépine.

32 records · Page 2Linked to original sources
PubMed1997

Anaerobic biodegradation of pentachlorophenol in a liquor obtained after extraction of contaminated chips and wood powder.

Recovery of 97.5% of the pentachlorophenol (PCP) in contaminated wood powder was obtained after extraction with 0.1% KOH solution at 60 degrees C for 75 min. Extraction with NaOH and Na2CO3 was less effective than KOH. The neutralized extract was treated using a methanogenic consortium in an upflow anaerobic fixed-film reactor. The reactor was operated at 29 degrees C for over 600 d. The best performance of the reactor was observed when the PCP liquor was supplemented with glucose and formate. Complete dechlorination of PCP and phenol removal was obtained for a PCP loading rate of 13.3-18.0 mg l(-1) of reactor volume d(-1) with recirculation of the effluent and a hydraulic retention time (HRT) of 0.5-0.6 d.

Bacteria, Anaerobic↗
PubMed1996

Isolation and characterization of Desulfitobacterium frappieri sp. nov., an anaerobic bacterium which reductively dechlorinates pentachlorophenol to 3-chlorophenol.

An anaerobic bacterium, strain PCP-1T (T = type strain), which dechlorinates pentachlorophenol (PCP) to 3-chlorophenol, was isolated from a methanogenic consortium. This organism is a spore-forming rod-shaped bacterium that is nonmotile, asaccharolytic, and Gram stain negative but Gram type positive as determined by electron microscopic observations. Inorganic electron acceptors, such as sulfite, thiosulfate, and nitrate (but not sulfate), stimulate growth in the presence of pyruvate and yeast extract. The optimum pH and optimum temperature for growth are 7.5 and 38 degrees C, respectively. The dechlorination pathway is: PCP-->2,3,4,5-tetrachlorophenol -->3,4,5-trichlorophenol-->3,5-dichlorophenol-->3-chlorophenol. This bacterium dechlorinates several different chlorophenols at ortho, meta, and para positions; exceptions to this are 2,3-dichlorophenol, 2,5-dichlorophenol, 3,4-dichlorophenol, and the monochlorophenols. The time course of PCP dechlorination suggests that two enzyme systems are involved in dehalogenation in strain PCP-1T. One system is inducible for ortho dechlorination, and the second system is inducible for meta and para dechlorinations. A 16S rRNA analysis revealed that strain PCP-1T exhibits 95% homology with Desulfitobacterium dehalogenans JW/IU-DC1, an anaerobic bacterium which can dehalogenate chlorophenols only in ortho positions. These results suggest that strain PCP-1T is a member of a new species and belongs to the recently proposed genus Desulfitobacterium. Strain PCP-1T differs from D. dehalogenans JW/IU-DC1 by its broader range of chlorophenol dechlorination. Strain PCP-1 is the type strain of the new species, Desulfitobacterium frappieri.

Bacteria, Anaerobic↗
PubMed1996

Isolation and characterization of a new bacterium carboxylating phenol to benzoic acid under anaerobic conditions.

A consortium of spore-forming bacteria transforming phenol to benzoic acid under anaerobic conditions was treated with antibiotics to eliminate the four Clostridium strains which were shown to be unable to accomplish this reaction in pure culture and coculture. Clostridium ghonii was inhibited by chloramphenicol (10 micrograms/ml), whereas Clostridium hastiforme (strain 3) and Clostridium glycolicum were inhibited by clindamycin (20 micrograms/ml), without the transformation of phenol being affected. Electron microscopic observations of resulting liquid subcultures revealed the presence of two different bacilli: a dominant C hastiforme strain (strain 2) (width, 1 micron) and an unidentified strain 6 (width, 0.6 micron) which was not detected on solid medium. Bacitracin (0.5 U/ml) changed the ratio of the strains in favor of strain 6. C hastiforme 2 was eliminated from this culture by dilution. The isolated strain 6 transformed phenol to benzoic acid and 4-hydroxybenzoic acid to phenol and benzoic acid in the presence of proteose peptone. Both of these activities are inducible. This strain is a gram- variable, flagellated rod with a doubling time of 10 to 11 h in the presence of phenol. It has a cellular fatty acid composition like that of C. hastiforme. However, strain 6 does not hydrolyze gelatin or produce indole. The 16S rRNA sequence of strain 6 was found to be most similar to that of some Clostridium species, with homology ranging from 80 to 86%. Tbe evolutionary relationships of strain 6 to different groups of Clostridium and Clostridium-related species revealed that it does not emerge from any of these groups. Strain 6 most likely belongs to a new species closely related to Clostridium species.

Anaerobiosis↗
PubMed1995

Study of the reductive dechlorination of pentachlorophenol by a methanogenic consortium.

Pentachlorophenol (PCP) dechlorination by a methanogenic consortium was observed when glucose, formate, lactate, or yeast extract was present in the mineral medium as a secondary carbon source. Acetate was not a good substrate to sustain dechlorination. The consortium was able to dechlorinate the different monochlorophenols, although the chlorine in position ortho and meta was removed more readily than in para position. Dechlorination was most efficient at 37 degrees C. At 45 degrees C, the first PCP dechlorination steps were very rapid, but 3,5-dichlorophenol (3,5-DCP) was not further dechlorinated. At 15 and 4 degrees C, dechlorination was very slow. The dechlorination of PCP to 3-chlorophenol (3-CP) was still observed after the consortium had been subjected to heat treatment (80 degrees C, 60 min), suggesting that spore-forming bacteria were responsible. The dechlorinating activity of the consortium was significantly reduced by the presence of hydrogen, 2-bromoethanosulfonic acid (BESA), or sulfate but not of nitrate. The dechlorination of 3-CP was completely inhibited by heat treatment or the presence of BESA, suggesting that a syntrophic microorganism would be involved. Vigorous agitation of the consortium stopped the dechlorination, but the presence of DEAE-Sephacel acting as a support was very efficient in restoring the activity, suggesting that association between certain members of the consortium was important.

Alkanesulfonic Acids↗
PubMed1993

Potential for carboxylation-dehydroxylation of phenolic compounds by a methanogenic consortium.

An anaerobic consortium that carboxylated and dehydroxylated phenol to benzoate, and 2-cresol to 3-methylbenzoic acid, under methanogenic conditions was studied. Phenol induced this transformation activity. Addition of 4-hydroxypyridine or an increase in the concentration of proteose peptone to 0.5% (w/v) delayed the transformation. Phenol enhanced the rate of transformation of 2-cresol whereas 2-cresol delayed the transformation of phenol. Phenols with ortho-substitutions (chloro-, fluoro-, bromo-, hydroxyl-, amino-, or carboxyl-) were transformed to meta-substituted benzoic acids. However, meta- and para-substituted phenols (cresols, fluorophenols, and chlorophenols) were not transformed. Phenol was most rapidly metabolized, followed by catechol, 2-cresol, 2-fluorophenol, 2-aminophenol, 2-chlorophenol, 2-hydroxybenzoic acid, and 2-bromophenol. The consortium O-demethylated anisole to phenol and 2-methoxyphenol to catechol, and oxidized 2-hydroxybenzyl alcohol to 2-hydroxybenzoic acid. Aniline, 2-ethylphenol, 2-hydroxypyridine, 2-acetamidophenol, 2,6-dimethylphenol, 2-phenylphenol, and 1-naphthol were not metabolized.

Aminophenols↗
PubMed1991

Carboxylation of o-cresol by an anaerobic consortium under methanogenic conditions.

The metabolism of o-cresol under methanogenic conditions by an anaerobic consortium known to carboxylate phenol to benzoate was investigated. After incubation with the consortium at 29 degrees C for 59 days, o-cresol was transformed to 3-methylbenzoic acid, which was not further metabolized by the consortium. Proteose peptone in the culture medium was essential for the transformation of o-cresol. In addition, a transient compound detected in the culture was identified as 4-hydroxy-3-methylbenzoic acid. o-Cresol-6d was transformed by the consortium to deuterated hydroxy-methylbenzoic acid and deuterated methylbenzoic acid. These results demonstrate that o-cresol is carboxylated in the para position relative to the phenolic hydroxyl group and dehydroxylated by the anaerobic consortium.

Bacteria, Anaerobic↗
PubMed1990

Degradation pathways of PCB upon gamma irradiation.

In order to understand the modifications of the chromatographic profile of Aroclor 1260 upon gamma irradiation, a total of 14 pure polychlorinated biphenyl (PCB) congeners were separately irradiated in solution. Dechlorination was observed, and the generated products were investigated by gas chromatography and mass spectrometry. Degradation proceeds more rapidly in methanol/water mixture than in petroleum ether, but the relative amount of ortho-dechlorinated congeners formed upon irradiation was smaller in the former solvent. Ortho chlorines are preferentially lost in petroleum ether except when they are involved in a 2.5 (or 3.6) substitution pattern, in which case para dechlorination becomes predominant. The precursors of some toxicologically important congeners such as congeners 77, 118, 167, and 189 have been identified. These data are useful to rationalize the modifications of the chromatographic profile of PCB complex mixture upon gamma irradiation.

Aroclors↗
PubMed1990

[Post-varicella anetoderma. 3 cases].

We report three cases of typical macular atrophy which appeared during, or was noticed shortly after varicella. The three patients were children. These cases were particular in that anetoderma lesions occurred independently of the scarring varicella lesions and followed a prolonged course of their own afterwards. We were unable to classify these cases in the primary or secondary type of macular atrophy. The various dermatoses associated with macular atrophy and the numerous physiopathological hypotheses put forward concerning this entity are enumerated.

Atrophy↗
PubMed1989

Catalase activity measurement with the disk flotation method.

Activity measurements of catalase are usually performed with a spectrophotometric method by monitoring the decrease of H2O2 at 240 nm. A different method presented here uses an instrument named Catalase-meter and yields flotation time data which are expressed in tenth of seconds. For the first time, solutions of catalase of different concentrations were tested simultaneously with the two methods, and the Catalase-meter's flotation data were submitted to correlation with international units calculated from spectrophotometric data. The corresponding calibration curve correlates flotation time data to international units. The r2 values thus obtained for the two calibration curves were 0.960 and 0.929, for a range of activity varying from 9.3 to 144.5 international units/ml.

Animals↗
PubMed1984

Synthesis and biological activity of monothionated analogs of leucine-enkephalin.

The synthesis of the four regioisomers of monothionated Leu-enkephalins (Leu-Enk) from previously reported protected precursors is described. The Tyr1-thio analog was obtained as a 1:1 mixture of the L- and D-Tyr diastereomers. The pure compounds were tested for opiate-like activity by using the guinea-pig ileum (GPI) and mouse vas deferens (MVD) preparations, by assessing analgesic effects following intra-cerebroventricular administration and by examining their ability to displace [3H]-D-Ala2, D-Leu5-enkephalin (DADLE) and [3H]-dihydromorphine from rat brain homogenates. The results demonstrate that depending on the backbone position of the thioamide function, activity can be decreased or increased. In the smooth muscle preparations as well as in the opiate binding tests, the activity of D,L-Tyr1-thio-Leu-Enk and Gly3-thio-Leu-Enk was reduced. The activity of the latter analog was also diminished in the analgesia test. In all biological assays, Phe4-thio-Leu-Enk was either equally or slightly less potent than the parent compound. However, introduction of the sulfur atom in position 2 of Leu-Enk increased the potency of the compound in all assays, the MVD assay being the most sensitive. The results are interpreted in terms of the thioamide (amide) function in receptor recognition processes, the probable behavior of thiopeptides toward physiologically relevant peptidases and the structural divergences between tissue-specific receptors.

Amino Acids, Sulfur↗
PubMedDate not supplied

Two-liquid-phase slurry bioreactors to enhance the degradation of high-molecular-weight polycyclic aromatic hydrocarbons in soil.

High-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) are pollutants that persist in the environment due to their low solubility in water and their sequestration by soil and sediments. The addition of a water-immiscible, nonbiodegradable, and biocompatible liquid, silicone oil, to a soil slurry was studied to promote the desorption of PAHs from soil and to increase their bioavailability. First, the transfer into silicone oil of phenanthrene, pyrene, chrysene, and benzo[a]pyrene added to a sterilized soil (sandy soil with 0.65% total volatile solids) was measured for 4 days in three two-liquid-phase (TLP) slurry systems each containing 30% (w/v) soil but different volumes of silicone oil (2.5%, 7.5%, and 15% [v/v]). Except for chrysene, a high percentage of these PAHs was transferred from soil to silicone oil in the TLP slurry system containing 15% silicone oil. Rapid PAH transfer occurred during the first 8 h, probably resulting from the extraction of nonsolubilized and of poorly sorbed PAHs. This was followed by a period in which a slower but constant transfer occurred, suggesting extraction of more tightly bound PAHs. Second, a HMW PAH-degrading consortium was enriched in a TLP slurry system with a microbial population isolated from a creosote-contaminated soil. This consortium was then added to three other TLP slurry systems each containing 30% (w/v) sterilized soil that had been artificially contaminated with pyrene, chrysene, and benzo[a]pyrene, but different volumes of silicone oil (10%, 20%, and 30% [v/v]). The resulting TLP slurry bioreactors were much more efficient than the control slurry bioreactor containing the same contaminated soil but no oil phase. In the TLP slurry bioreactor containing 30% silicone oil, the rate of pyrene degradation was 19 mg L(-)(1) day(-)(1) and no pyrene was detected after 4 days. The degradation rates of chrysene and benzo[a]pyrene in the 30% TLP slurry bioreactor were, respectively, 3.5 and 0.94 mg L(-)(1) day(-)(1). Low degradation of pyrene and no significant degradation of chrysene and benzo[a]pyrene occurred in the slurry bioreactor. This is the first report in which a TLP system was combined with a slurry system to improve the biodegradation of PAHs in soil.

Biodegradation, Environmental↗