Microbial dehalogenation of polychlorinated biphenyls in aerobic conditions / Dehalogenación microbiana de bifenilos policlorados en condiciones aeróbicas

From soils contaminated with polychlorinated biphenils (PCBs) a strain of Alcaligenes sp. able to grow in a mineral medium with a commercial mixture of PCBs as carbon source was isolated. This strain consumed up to 200 ppm in seven days in laboratory conditions. After 24 h of incubation, some new congeners of PCBs could be recognized by mass spectrometry. Through the identification of these compounds it was possible to postulate examples of possible transformations by dechlorinations of penta- and tetra-chlorinated congeners into tri-chlorinated ones. The properties of the isolated strain are appropriate for bioremediation of contaminated areas and also for using in bioreactors in order to remove the xenobiotic chemical.

A partir de suelos contaminados con bifenilos policlorados (PCBs) se aisló una cepa de Alcaligenes sp. capaz de crecer en medio mineral con una mezcla comercial de PCBs como fuente de carbono. Esta cepa consumió hasta 200 ppm de PCBs en siete días de incubación en condiciones de laboratorio. En 24 horas de incubación se han podido detectar nuevos congéneres de PCBs mediante espectrometria de masa. La identificación de estos compuestos ha permitido postular transformaciones de congéneres penta- y tetra-clorados que originarían derivados triclorados. Las propiedades de la cepa aislada son apropiadas para biorremediación y para su uso en biorreactores para eliminar estos compuestos xenobióticos.

Degradation of environmental pollutants by Trametes trogii

The ability of the ligninolytic fungus Trametes trogii to degrade in vitro different xenobiotics (PCBs, PAHs and dyes) was evaluated. Either 200 ppm of a PCB mixture (Aroclor 1150) or 160 ppm of an industrial PAH mixture (10 V/V of PAHs, principal components hexaethylbenzene, naphthalene, 1-methyl naphthalene, acenaphthylene, anthracene, fluorene and phenanthrene), were added to trophophasic and idiophasic cultures growing in a nitrogen limited mineral medium (glucose/asparagine) and in a complex medium (malt extract/glucose). Gas-liquid chromatography proved that within 7 to 12 d more than 90 of the organopollutants added were removed. The decrease in absorbance at 620 nm demonstrated that cultures of this fungus were able to transform 80 of the dye Anthraquinone-blue (added at a concentration of 50 ppm) in 1.5 h. Enzyme estimations indicated high activity of laccase (up to 0.55 U/mL), as well as lower production of manganese-peroxidase. Laccase activity, detected in all the conditions assayed, could be implicated in the degradation of these organopollutants. Considering the results obtained, T. trogii seems promising for detoxification.

Use of a CO2 electrode to monitor fermentations that use xenobiotic compounds as source of carbon

Bacterial strains were isolated from contaminated waters, mud or soils. They are capable of growing in mineral medium with different chemicals as carbon source, such as aliphatic or aromatic hydrocarbons and polychlorinated biphenyls (PCBs). Most of these strains tolerate high concentrations (up to 30 v/v) of the xenobiotic substrates. This is particularly important for the development of fermenting processes to treat effluents or residues with a high content of contaminating compounds. An ion-specific potentiometric electrode (CO2) has been developed to measure CO2 production continuously. When the different strains were incubated in a mineral medium and in the presence of the corresponding substrate, a parallel between growth, substrate consumption and CO2 production was found. The developed system is suggested as an efficient and economical alternative to evaluate the potential of biodegradation by different microorganisms.

Degradación de azui de antraquinona por Trametes trogii / [Degradation of anthraquinone blue by Trametes trogii]

The ability of the white rot fungus Trametes trogii BAFC 463 (high producer of ligninolytic enzymes, especially laccase and manganese peroxidase) to degrade the dye anthraquinone blue, refractory to bacterial attack, was evaluated. Both tropho- and idiophasic T. trogii cultures in synthetic medium (glucose/asparagine) and complex medium (malt extract/glucose) were able to transform up to 88

dye in 4 hours. The activity of laccase, an oxygen-dependent phenoloxidase which was present at high levels in all the conditions assayed, might be related to the ability of the fungus to degrade the colorant. This is supported by the fact that in bioreactor experiences carried out at pH 4.5 the addition of anthraquinone blue caused a decrease in the levels of soluble oxygen. However, although high levels of laccase were produced at pH 7.5, the enzyme was not active, and neither dye transformation nor loss in the levels of soluble oxygen were quantified.

Degradación de ácido naftalén-2-sulfónico por cepas de Micromonospora / Naphthalen-2-sulfonate degradation by Micromonospora strains

De aguas del Río Reconquista se han podido aislar cepas de Micromonospora resistentes a altos niveles de cromo y otros metales pesados, capaces de crecer sobre ácido naftalén-2-sulfónico como única fuente de carbono. Este fenotipo es muy estable, lo que hace a este microrganismo interesante desde el punto de vista de la eliminación de residuos industriales que contengan este tipo de sustancias. La biodegradación procede mediante la formación de ácido salicílico y ácido gentísico como intermediarios, metabolitos que han sido aislados mediante cromatografía gaseosa y caracterizados mediante espectroscopía de masa

Biodegradación de una mezcla comercial de bifenilos policlorados / Biodegradation of a commercial mixture of polychlorinated byphenyls

De suelos contaminados con bifenilos policlorados (PCBs) se ha aislado una cepa de Klebsiella oxytoca que crece en un medio mineral con una mezcla comercial de PCBs como única fuente de carbono. La mezcla utilizada contiene una variedad de congéneres de bifenilos bi-, tri-, y tetraclorados, siendo los triclorados los constituyentes mayoritarios. La cepa aislada puede crecer también con 6-cloroquinolina, y menos eficientemente, con clorobenceno. En ensayos de consumo en frasco, el microorganismo degrada los PCBs casi completamente en tres días. En estas condiciones se forman compuestos acídicos y/o fenólicos que son degradados en siete días de incubación

A decalin-consuming bacterial community

A bacterial community able to degrade cis- and trans-decalin (decahydronaphthalene) in the presence of n-decane could be isolated. It was composed by a couple of Pseudomonas strains (D1 and D2, respectively). Neither the community nor the isolated strains were able to grow on decalin alone. D1 grew on decalin plus n-decane. Both could grow on n-decyl alcohol, acetate and adipate. From hydrocarbonated substrates it would be generated a metabolic chain which allows the growth of the community members, and then it resulted to be stable. Characteristics of both strains are described.

Microorganismos degradadores de ácido naftalen-2-sulfónico / [2-Naphthalene-sulphonic acid degrading microorganisms]

Derivatives of anionic surfactants, specially naphthalene sulphonates, when discharged into natural waters are accumulated in waters and sediments because of their poor biodegradability. A four-membered bacterial community, able to degrade the sodium salt of 2-naphthalene-sulphonic acid (2NS), was isolated from Río Reconquista. All the isolated strains consisted of gram-negative, strictly aerobic rods, with a strong proteolytic activity and resistance to high levels of cations like Cr (III), Hg (II), Cd (II) and Pb (II). Some of them were resistant to gentamicin, amikacin and chloramphenicol. These strains appeared to be related to the genera Pseudomonas and Alcaligenes. When isolated, if growing on 2NS, a brown-dark pigment is formed by three of them, resulting in an inhibition of growth. The presence of a Pseudomonas aeruginosa strain avoided the production of pigment and resulting in a complete consume of 2NS.

Algunas propiedades de la delta-aminolevulinato sintetasa de Rhodopseudomonas palustris / [Various properties of delta-aminolevulinate synthetase from Rhodopseudomonas palustris]

The enzymatic formation of delta-aminolevulinic acid (ALA) in extracts of Rhodopseudomonas palustris has been studied. Some properties of delta-aminolevulinate synthetase (ALA-S), including molecular weight km for glycine and the inhibition of enzyme activity by ALA are reported.