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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: screening tests
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP, non-guideline study, published in peer-reviewed literature, no restrictions, fully adequate for assessment.

Data source

Reference
Reference Type:
publication
Title:
Aerobic degradation of ethyl-tert-butyl ether by a microbial consortium: selection and evaluation of biodegradation ability
Author:
Kharoune M, Kharoune L, Lebault J-M and Pauss A
Year:
2002
Bibliographic source:
Environmental Toxicology and Chemistry, Vol. 21, No. 10, pp. 2052-2058

Materials and methods

Principles of method if other than guideline:
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. Ten respirometer flasks containing the target substrates were inoculated with defined biomass concentration. Two other respirometer flasks were used as controls, one receiving biomass only (endogenous respiration control) and the other receiving the target substrates only (abiotic control, poisoned with 1% NaCN). The substrates’ degradations were monitored by collecting oxygen uptake data (all flasks) and periodically sampling
the levels of cell protein and dry weight, pH, residual substrates, and soluble oxygen chemical demand (COD) concentrations. Random sampling was performed, with a single
test flask sacrificed at each sampling time. Triplicate or two duplicate experiments were performed simultaneously for each experiment.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Purity: >97%
Supplier: Fluka (Lyon, France)

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
other: consortium from a gasoline-polluted soil
Details on inoculum:
One gram of soil from the upper surface layer was placed in 500-ml Erlenmeyer flasks containing 100 ml of the mineral salts medium with 10 mg/L of ETBE and sealed with Teflont-lined screw caps. After 5 d of incubation at 22 ± 2 ºC at an agitation speed of 100 rpm, 10 ml of the enrichment culture was transferred to 90 ml of fresh medium containing 10 mg/L of ETBE. After several transfers in liquid culture, samples were plated in a medium containing mineral salts, 50 mg/L of ETBE, and 15 g/L of purified agar (Difco Laboratories, Paris, France). Growth on the plates was very slow. All colonies appearing after two weeks of incubation at 22 ± 2 ºC were suspended in mineral medium, harvested by centrifugation (12,225 g for 15 min at 4 ºC), washed, and transferred back to a liquid culture containing about 200 mg/L of ETBE. Several transfers enriched the ETBE-degrading microorganisms and improved their degradation ability. The selected microbial consortium grew on ETBE without supplemental carbon sources or growth factors.
Duration of test (contact time):
ca. 30 h
Initial test substance concentration
Initial conc.:
150 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
All the batch experiments were carried out in a BSB digi V 1.01t electrolytic respirometer (Bioblock Scientific, Illkirch, France) at 280 ºC at an agitation speed of 125 rpm. Ten respirometer flasks containing the target substrates were inoculated with defined biomass concentration. Two other respirometer flasks were used as controls, one receiving biomass only (endogenous respiration control) and the other receiving the target substrates only (abiotic control, poisoned with 1% NaCN). The substrates’ degradations were monitored by collecting oxygen uptake data (all flasks) and periodically sampling the levels of cell protein and dry weight, pH, residual substrates, and soluble oxygen chemical demand (COD) concentrations. Random sampling was performed, with a single test flask sacrificed at each sampling time. Triplicate or two duplicate experiments were performed simultaneously for each experiment.

Results and discussion

% Degradation
Parameter:
% degradation (O2 consumption)
Value:
100
Sampling time:
30 h
Details on results:
Experiments with TAME as individual substrate showed that the consortium degrade TAME without a lag period and without the appearance of major by-products like TAA for TAME degradation (data not given). The degradation rate was dependent on the nature of the initial substrate. During the experiments, the abiotic removal of TAME was about 3 to 4%.
The observed substrate degradation rate of TAME was 1.5 ± 0.1 mg/L/h, the soluble COD rate was 3.6 ± 0.3 mg/L/h and the oxygen uptake rate was 4 ± 0.5 mg/L/h.

Applicant's summary and conclusion