The objective of this study was to examine the potential for degradation of mixtures of pesticides (chlorpyrifos, linuron, metribuzin) by a range of bacteria and fungi and to relate this capability to enzyme production and quantify the rates of degradation of the components of the mixture of xenobiotic compounds. Overall, although bacteria (19 Bacillus and 4 Pseudomonas species) exhibited tolerance to the individual and micture of pesticides actual degradation was not evident. Five species of white rot fungi were grown on minimal salts agar plates amended with 0, 10 and 30 mg L-1 of chlorpyrifos, linuron and metribuzin, individually and as a mixture with a total concentration 15 and 30 mg L-1. Four of these, T. versicolor, P. gigatea, P.coccineus and P.ostreatus, exhibited very good tolerance to the pesticides. They were also grown on a nutritionally poor soil extract agar amended with a mixture of the pesticides at different concentrations (0-70 mg L-1). Subsequently, the ability of T. versicolor, P. gigatea, P. coccineus to degrade lignin and production of laccase in the presence of mixture of the pesticides was examined as well as their capacity to degrade the pesticide mixture at different concentrations (0-50 mg L-1) in soil extract broth was quantified using HPLC. This showed that only T.versicolor had the ability to degrade linuron, after three weeks incubation although all tested species produced laccase. Subsequently, the temporal degradation rates of T.versicolor was examined in relation to temporal degradation of a mixture of the pesticides chlorpyrifos, linuron and metribuzin with total concentrations 0-50 mg L-1 and the temporal laccase production was quantified over a six week period in relation to ionic and non-ionic water potential stress (-2.8 MPa). These studies showed that the test isolate had the ability to produce very high levels of laccase at -2.8 MPa water potential adjusted non-ionically by using glycerol and quite lower levels in soil extract broth without stress while T.versicolor did not produce laccase at -2.8 MPa when the medium was modified ionically. Finally, T.versicolor was able to degrade the pesticide linuron in all tested water regimes, after five weeks incubation, regardless of the concentration of the mixture. In contrast, about 50% of the metribuzin was degraded, only at at -2.8 MPa water potential adjusted non-ionically with glycerol. Chlorpyrifos and its main metabolite TCP were not detected, possibly, due to a combination of hydrolysis, photolysis and volatilization degradation. The capacity of T.versicolor to degrade linuron in mixtures of pesticides and the production of high levels of laccase, in a nutritionally poor soil extract broth, even under water stress suggests potential application of this fungus in bioremediation.

Le chlordécone est un pesticide organochloré, qui a été utilisé dans les Antilles françaises pour lutter contre le charançon du bananier Cosmopolites sordidus. Ce pesticide a été interdit en 1993 en raison de sa toxicité et de sa persistance dans l'environnement. Cependant des études ont montré que la population antillaise continue d'être exposée (lait maternel et sang contaminés, transfert de chlordécone mère-jeune, retard du développement cognitif, risque de cancer de la prostate) en particulier via l'alimentation. Depuis 2008, la réglementation européenne n°396/2005 est appliquée sur le territoire antillais (limite maximale fixée à 10 et 20 µg chlordécone /kg poids frais repsectivement dans le foie et l'oeuf et de 100 µg/kg de matière grasse dans le gras). Il s'avère que la contamination des denrées au chlordécone est due au fait que les sols d'anciennes bananeraies autrefois traités au chlordécone (principalement des andosols, des nitisols et des ferrisols) demeurent contaminés. L'andosol contient de l'argile allophane, structure qui confère une microporosité élevée par l'enchevêtrement de motifs particulaires répétés à plusieurs échelles. Le chlordécone de l'andosol a été potentiellement piégé par ce réseau de micropores et est supposé être fortement retenu. Au contraire, le nitisol contient de l'argile halloysite, dont la structure correspond à une superposition de couches et ménage une faible porosité. Notre hypothèse est que le chlordécone est moins retenu par le nitisol que par l'andosol. Les animaux monogastriques élevés en plein air (porcin, volaille) sont susceptibles d'ingérer du sol de manière involontaire. Chez la poule pondeuse, les niveaux d'ingestion de sol peuvent atteindre 25 % de la ration alimentaire journalière dans le cas d'une réduction du couvert végétal et/ou d'un rationnement alimentaire. L'ingestion de sol pour le porcin a été peu étudiée. Nous avons cherché à déterminer les aptitudes d'un andosol et d'un nitisol à retenir le chlordécone durant le processus digestif. Pour cela nous avons évalué la biodisponibilité relative du chlordécone d'un andosol et d'un nitisol chez l'animal monogastrique. La détermination de la biodisponibilité relative repose sur la comparaison des pentes entre la réponse (concentration de chlordécone dans les matrices animales) obtenue lors des doses croissantes de chlordécone ingérées via la matrice testée (l'andosol ou le nitisol) à la réponse obtenue lors des mêmes doses de chlordécone ingérées via une matrice de référence (huile). Les résultats obtenus chez la poule pondeuse et le porcelet ont indiqué que l'andosol et le nitisol n'affectent pas la biodisponibilité du chlordécone. Ainsi, la biodisponibilité relative du chlordécone des sols étudiés a été identique et considérée égale à 100% aussi bien chez la poule que chez le porcelet. Le chlordécone du sol a donc été extrait durant le processus digestif et absorbé par l'animal monogastrique à l'identique du chlordécone dissous dans de l'huile. Le chlordécone du sol est donc assimilable par l'animal d'élevage. Ainsi, les sols contaminés en chlordécone présentent un réel risque pour la filière animale. Les teneurs en chlordécone des produits (foie, gras, oeuf) ont dépassé les limites maximales acceptables dès lors que les animaux monogastriques ont ingéré 6,8 µg chlordécone /jour/kg de poids vif. Sachant que 10% des sols cultivables contiennent au moins 1 mg chlordécone /kg, dès lors qu'un animal monogastrique (poule pondeuse ou porcelet) ingère 17 % de sol dans sa ration alimentaire quotidienne, les teneurs en chlordécone des produits dépasseront les limites maximales et seront « impropres » à la consommation. Il convient ainsi d'identifier les pratiques d'élevage à risques pour préconiser des mesures limitant la contamination des produits animaux au chlordécone / Chlordecone (CLD) is an organochlorine pesticide used in the French West Indies against black weevil Cosmopolites sordidus. This pesticide was banned in 1993, because of the toxicity and persistence of this compound in the environment. However, several studies indicated that the population is already exposed to chlordecone (contaminated blood and maternal milk, chlordecone transfer to the mother from the child, memory delay in child and risk to the prostate cancer) particularly by food ingestion. Since 2008, European Regulation °396/2005 is applied in French West Indies (maximal limit fixed at 10 and 20 µg chlordecone/kg of fresh weight in liver and egg and at 100 µg chlordecone /kg of fat in fat). Soils of banana crops previously treated by chlordecone (mainly andosols, nitisols, ferrisols) are still contaminated and are the major source of contamination of food products. Andosol contains allophane clay structure which allows a high microporosity with the formation of particle aggregates in a pattern repeated at different scales. chlordecone would be strongly trapped by this micropores structure and supposed to be strongly retained. Nitisol contains halloysite clayed structure composed to the clay layers superposition with a low porosity. Our hypothesis is that chlordécone is less retained by nitisol than by andosol. Monogastric animals reared outside (pig, poultry) may involuntary ingest soil. It has been shown that hen can ingest soil amounts corresponding to 25 % of the daily ration in the case of vegetation reduction and of nutritional imbalance. Soil ingestion by pig was less studied. In the frame of this research work, we determined andosol and nitisol capacities to retain chlordecone during the digestive process. The relative bioavailability of soil-bound chlordecone in monogastric farm animals (laying hen and juvenile swine) was established. The relative bioavailability determination consists to the slope comparison between the response (concentrations of chlordecone in animal matrices) obtained with increasing chlordecone doses via andosol or nitisol and the response obtained with the same chlordecone ingestion doses via a reference matrix (oil). Results showed that andosol and nitisol did not reduce the chlordecone bioavailability. Thus, relative bioavailability of soil-bound chlordecone was considered to be equal to 100% in laying hen and in juvenile swine. chlordecone was extracted during the digestive process and was absorbed by the monogastric animals. Thus, soil-bound chlordecone is directly assimilated by monogastric farm animals. Concentrations of chlordecone in animal products (liver, fat, egg) exceeded maximal limits for a chlordecone ingestion at least equal to 6.8 µg chlordecone/day/kg of body weight. Since 10% of agricultural soils are contaminated with at least 1 mg/kg, the ingestion of 17% of soil in the daily food ration will result in animal products not acceptable for human consumption. Therefore, it is important to characterize the risk livestock farming practices in order to limit the contamination of food products