AEROBIC DEGRADATION OF ETHYL-tert-BUTYL ETHER BY A MICROBIAL CONSORTIUM: SELECTION AND EVALUATION OF BIODEGRADATION ABILITY

Abstract

A microbial consortium that degrades ethyl-tert-butyl ether (ETBE) as the sole source of carbon and energy under aerobic conditions was selected from a gasoline-polluted soil. This consortium consists of a variety of microorganisms with a predominance of filamentous morphology. Degradation of ETBE was found to be solely related to bacterial activity. After prolonged cultivation followed by successive transfers, the consortium's degradation ability was improved and reached a specific degradation rate of 95 mg/g(protein)/h (about 146 mg/g(dry wt)/h). This exceeds the previously reported rates in the literature for ETBE-degrading microorganisms as pure or mixed cultures. Furthermore, a stoichiometric balance of chemical oxygen demand (COD) removal and oxygen uptake with ETBE removal provides indirect evidence of complete degradation. The consortium's activity was not inhibited by high ETBE concentrations (< or = 1,600 mg/L), and large inoculum sizes (> or = 120 mg(protein)/L) were desirable for a faster and complete degradation of ETBE. The enriched consortium was also able to completely degrade methyl-tert-butyl ether (MTBE), tert-amyl methyl ether (TAME), and tert-butyl alcohol (TBA). both alone and in mixture with ETBE, without any measurable release of major degradation intermediates. In each case, MTBE and TAME exhibited the most significant resistance to degradation while TBA was rapidly degraded.

Combining Radon Deficit, NAPL Concentration, and Groundwater Table Dynamics to Assess Soil and Groundwater Contamination by NAPLs and Related Attenuation Processes

“…Since a direct correlation was found between the depth of the groundwater and the concentrations of ETBE and total hydrocarbons, with approximately zero scores for radon and MTBE levels, we can attribute this component to a degradation process of the first two substances in aerobic conditions. Precipitations (consistent with a reduction in the groundwater depth) introduced oxygen and nutrients into the aquifer promoting rapid biodegradation of ETBE and total hydrocarbons in the vadose zone, with reduced efficiency for MTBE [34,35]. The additions of biosurfactants (natural extracts of marine algae and plants) improved the separation and dispersion of hydrocarbon blobs, allowing the development and growth of natural microorganism that further degraded the NAPLs.…”

Degradación de metil tert-butil éter (MTBE) y otros oxigenantes de la gasolina por hongos filamentosos

“…No se detectó citocromo P-450 en este cultivo. Kharoune et al (2002) obtuvieron un consorcio microbiano de un suelo contaminado con gasolina capaz de degradar ETBE como única fuente de carbono y energía. Este consorcio también logró degradar MTBE, TAME y TBA como únicas fuentes de carbono y energía en cultivos por lotes sin una fase lag.…”