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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
25 September - 8 December 2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study has been performed according to OECD 310 guidelines and according to GLP principles

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2014
Report Date:
2014

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Deviations:
yes
Remarks:
But no effect on the final outcome of the study.
Qualifier:
according to
Guideline:
other: ISO Standard 14593 (1999) - Method by analysis of inorganic carbon in sealed vessels (CO2 headspace test)
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
Name of test material (as cited in study report): Yeast extract (SPRINGER 0251 / 0-MG-L)
- Substance type: Powder
- Physical state: light brown powder
- Analytical purity: Not indicated by the sponsor; treated as 100% pure
- Lot/batch No.: 071403960
- Expiration date of the lot/batch: 31 August 2017
- Stability under storage conditions: stable
- Storage condition of test material: At room temperature
- Solubility in water: very soluble (> 10000 mg/L) at 50°C and pH 5 to 5.5

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Source : activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', Heeswijk Dinther, The Netherlands, receiving predominantly domestic sewage
Treatment : The freshly obtained sludge was used immediately. The concentration of suspended solids was 3.9 g/l in the concentrated sludge (information obtained from the municipal sewage treatment plant). Before use, the sludge was allowed to settle (35 minutes) and the liquid was decanted for use as inoculum at the amount of 10 ml/l of mineral medium.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
20 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
inorg. C analysis
Remarks:
After addition of NaOH and shaking for 1 hour, the bottles were allowed to settle. Then the supernatant was used for IC analysis.
Details on study design:
Inoculum blank: containing inoculated medium
Procedure control: containing inoculated medium and reference substance
Test substance: containing inoculated medium and test substance
Toxicity control: containing inoculated medium, reference substance and test substance

Per series, five test bottles for analysis at the end of the test and three test bottles for all other time intervals.
Incubation at 20°C , in the dark on an orbital shaker.

Analysis performed on day 1, 7, 16, 21 and 28 for inoculum blank, test substance and toxicity control
Analysis performed on day 1, 16 and 28 for the procedure control.

Measurements of pH: At the start of the test, in one additional vessel identically prepared to the bottles of each test series. Since all bottles of the test series were already closed, it was decided to determine the pH in an extra vessel that was identically prepared to the bottles to each test series.
Due to problems with the Shimadzu TOC-VCPH total organic carbon analyzer it was not possible to take and analyse samples on day 14. Samples were taken and analysed on day 16.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Test performance:
At the start of the test period the pH values of the different test media were all 7.7.
The temperature, recorded in a vessel with water in the same room, varied between 19.6 and 20.5°C

Measurements of pH: At the start of the test, in one additional vessel identically prepared to the bottles of each test series. Since all bottles of the test series were already closed, it was decided to determine the pH in an extra vessel that was identically prepared to the bottles to each test series.
Due to problems with the total organic carbon analyzer, samples were taken and analysed on day 16 instead of day 14. Therefore, the first acceptability criterion was evaluated by extrapolation. More than 60% biodegradation of Yeast extract was already reached on day 7 and the first acceptability criterion was met. Thus, there was no effect on the final outcome of this study.
% Degradation
Parameter:
% degradation (inorg. C analysis)
Value:
72
Sampling time:
28 d
Details on results:
The reference substance reached the level for ready biodegradability (>60%) within 14 days (day 14 = 66% biodegradation, extrapolated value).
The mean amount of TIC present in the blank controls at the end of the test was < 3 mg C/l (2.1 mg C/l) .
Since all criteria for acceptability of the test were met, this study was considered to be valid.

BOD5 / COD results

Results with reference substance:
76.2 % biodegradation in 28 days and 66% in 14 days (extrapolated value)

Any other information on results incl. tables

Biodegradation on various days during the 28-day period of incubation :

Nominal day

% Biodegradation

Reference substance

Yeast extract

Toxicity control

1

-0.2

26.8

40.8

7

N.a.

73.9

74.7

16

76.1

68.7

71.0

21

N.a.

70.4

71.0

28

76.2

72.0

64.8

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The Yeast extract, Saccharomyces cerevisiae, (SPRINGER 0251 / 0-MG-L) was readily biodegradable under the conditions of the OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test).
Executive summary:

The Yeast extract, Saccharomyces cerevisiae, (SPRINGER 0251 / 0-MG-L) was tested for ready biodegradability according to the OECD guideline No. 310, 2006, and ISO International Standard 14593, 1999, and following the GLP. This study was requested by ECHA in the decision CCH-D-0000004821 -76-02/F.

The tested substance was an UVCB, easily soluble in mineral medium. No correction was made for the purity/composition of the test substance. In a pre-test the TOC concentration of 5 g Yeast extract/l was determined to be 2040 mg/l. This value was used to set the concentration in the main test. 

In the main test, Yeast extract was added to mineral medium to give a final organic carbon concentration of 20 mg C/l. The test media were prepared using a 100-times concentrated stock solution, a clear yellow stock solution of 5 g Yeast extract/l. Volumes of 1.07 ml of this stock solution were added to mineral medium inoculated with a mixed population of micro-organisms (final volume 107 ml). The test was performed in sealed bottles with a headspace of air. 

The test consisted of four groups:

  1. Test substance: bottles each containing Yeast extract at 20 mg C/l,
  2. Toxicity control: bottles each containing Yeast extract at 20 mg C/l and sodium benzoate at 20 mg C/l,
  3. Procedure control: bottles each containing sodium benzoate at 20 mg C/l,
  4. Blank control: bottles containing untreated mineral medium.

The CO2 evolution resulting from the aerobic biodegradation of the test substance was determined by measuring the inorganic carbon (IC) produced in the test bottles in excess of that produced in blank vessels containing inoculated medium only. The extent of biodegradation was expressed as a percentage of the theoretical maximum IC production, based on the quantity of test substance initially added (as organic carbon).

The relative biodegradation values calculated from the measurements performed during the test period revealed 72% biodegradation of Yeast extract at the end of the test. Furthermore, biodegradation of Yeast extract of at least 60% was reached within a 10-day window. In the toxicity control,Yeast extractwas found not to inhibit microbial activity. Since all criteria for acceptability of the test were met, this study was considered to be valid.

In conclusion, Yeast extract is designated as readily biodegradable, fulfilling the 10-day window.