Biodegradación de hidrocarburos aromáticos policíclicos y su aplicación en la biorremediación de suelos y lodos contaminados / Biodegradation of polycyclic aromatic hydrocarbons and its application to bioremediation of contaminated soils and sludges

Los hidrocarburos aromáticos policíclicos (HAPs) son un grupo de contaminantes prioritarios debido a sus propiedades tóxicas, mutagénicas y cancerígenas. Se encuentran en alta concentración en muchos suelos y lodos, principalmente aquellos asociados con las industrias del petróleo, producción de gas y preservación de la madera. El uso de microorganismos para la remediación de suelos y lodos contaminados está ganando interés como una técnica promisoria en comparación con prácticas convencionales como el relleno en tierra, la incineración o la extracción por solvente. Este artículo revisa las variables que controlan la biodegradación en fase sólida y en fase barro. La aceptación de la biorremediación exige demostrar: eficiencia, confiabilidad, predictibilidad de su desempeño de campo a partir de estudios de laboratorio y ventaja económica. Su efectividad puede ser reducida debido a algunas limitaciones en la biodegradación de HAPs de alto peso molecular y a fallas en el control de factores que dependen de la escala (transporte de masa, heterogeneidades espaciales, pérdidas abióticas). Se revisa también la metodología usada en la evaluación sistemática de la biorremediación

Study of Bacillus sp. culture conditions to promote production of unhairing proteases

The substitution of chemical depilatory agents in the leather industry by proteolytic enzymes produced by Bacillus species has an important economical and environmental impact. In previous assays, a Bacillus sp. showing a promising depilatory activity was isolated. In this paper, a culture medium that stimulated the synthesis and segregation of depilatory proteases, was selected. The influence of pH, oxygen supply rate (KLaC*), and inoculum age was evaluated on cell growth and protease production. Assays were carried out in lab bioreactors (1.2-1.4 l) at 37 degrees C. Five different media that differed in carbon and nitrogen sources were tested. pH ranged from 4.0 to 8.5. KLaC* varied between 40 and 470 mmol/lh. The best medium culture for protease production contained: nutrient broth (Britania) 8 g/l, yeast extract (Britania) 3 g/l, and mineral salts. Protease production was more effective at pH of 6.7, KLaC* of 360 mmol/lh, and inoculum age of 12 hours. These experimental conditions led to the following results: maximum proteolytic activity 2700 U/ml, overall volumetric protease productivity 300 u/ml-h, average specific growth rate 0.62 h-1, and average specific protease production rate 2.50 x 10(5) U/gh.

Biodegradabilidad en suelo de hidrocarburos residuales en fondos de tanques de almacenamiento de petróleo / [Biodegradability in soil of residual hydrocarbons in petroleum tank bottoms]

Biodegradability of hydrocarbons on soils can be applied to the treatment of residues (land treatment) from petroleum refinery as well as the cleaning of contaminated soils (bioremediation). In this paper we have studied the biodegradability of hydrocarbons from petroleum tank bottom sludges on soil by the autochthonous microbial community. Lab assays were conducted in 1l-beakers under the following conditions: hydrocarbon load 5.3

, total aerobic microorganisms 2.7 x 10(7) CFU/g, hydrocarbon degrading microorganisms (HDM) 2.5 x 10(5) cells/g, incubation temperature 25 degrees C, pH 7.0-7.6, and moisture 10-15

. Soil had the following composition: sand 25

, and clay 20

. Different levels and kind of fertilizers were evaluated. Fertilization increased the rate and the quantity of hydrocarbons degraded. It was degraded about 40

of hydrocarbons in 30-90 days according to the fertilization effected. During biodegradation, the HDM increased 760 times. Assays conducted outdoor on trays showed a similar limit of biodegradation. Changes with time in the fungi population, hydrocarbon class, carbon level, and saturated hydrocarbon profiles were measured too. Data suggests the use of microorganisms having a greater metabolic capacity, specially to degrade those hydrocarbon classes that they have shown to be more resistant to biodegradation (aromatics, resins and asphaltenes).