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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
15 February - 22 March 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
TEST MATERIAL : Harpin-ab Fermentation Extract
- Lot No. of test material: R134-2
- Expiration date of the lot: July 2018
- Storage: -70°C, protected from light
- Active ingredient: 0.4% Harpin-ab proteins
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge : Aerobic sludge from the mixed treatment plant of urban (about 66%) and industrial (about 34%) liquid sewage situated at San Rocco, Monza (MB), Italia.
- Preparation of inoculum for exposure: The sludge samples were centrifuged, washed and analyzed to quantify the suspended solids concentration for the inoculum preparation.
- Concentration of sludge: 4 mg/L suspended solids
Duration of test (contact time):
28 d
Initial conc.:
25.67 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: The media were prepared as recommended in the guideline.
- Test temperature: 20°C
- pH: Not specified
- Aeration of dilution water: Not specified
- Suspended solids concentration: The sample has been used with the measured initial concentration of 25.67 mg/L of organic carbon (TOC).
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Glass bottles with hermetic seal
- Number of culture flasks/concentration: 17 flasks were used (3 replicates checked once a week; 5 replicates checked on day 28)
- Method used to create aerobic conditions: Not specified
- Measuring equipment: Determination of total inorganic carbon was performed using an automatic TOC analyser.
- Test performed in open system: No
- Details of trap for CO2 and volatile organics if used: Not specified

SAMPLING
- Sampling frequency: The concentration of inorganic carbon (TIC) was measured weekly.
- Sampling method: At least 12 hours before every determination of inorganic carbon (TIC) the reaction in one bottle of blank, one of reference substance and one of the test item was stopped with the addition of 6 mL of sodium hydroxide (1 M).

CONTROL AND BLANK SYSTEM
- Inoculum blank: Water containing the culture medium and the inoculum of the sludge; 3 replicates checked once per week; 5 replicates checked on day 28
- Abiotic sterile control: Test item and 50 mg/L HgCl2; 3 replicates checked on the first day; 5 replicates checked on day 28
- Toxicity control: No
Reference substance:
benzoic acid, sodium salt
Remarks:
A nominal concentration of 24.17 mg/L of organic carbon (TOC) was used
Key result
Parameter:
% degradation (TOC removal)
Value:
88
Sampling time:
28 d
Results with reference substance:
The percentage of average degradation of the reference substance was 83% after 28 days of incubation.

The trend of the inorganic carbon and related biodegradation percentages in the bottle containing both the test sample and the reference substance confirm the absence of inhibitory effect of the test sample on the inoculum.

Abiotic degradation did not occur because the amount of TIC during the test in the abiotic bottles was lower than 10%.

Table 1: Biodegradation results

Check point (Days)

% biodegradation

Reference substance

% biodegradation

Test item

% biodegradation

Reference substance + Test item

0

0

0

0

1

8

31

41

7

69

78

-

14

88

93

-

21

84

90

-

28

83

88

83

Validity criteria fulfilled:
yes
Remarks:
The mean amount of TIC present in the blank controls at the end of the test is <3 mg C/l and the percentage of average degradation of the reference substance is more than 60% after 14 days of incubation.
Interpretation of results:
readily biodegradable
Conclusions:
On the basis of results obtained, the test item “Harpin-ab Fermentation Extract” should be considered readily biodegradable under aerobic conditions.

Description of key information

A ready biodegradation study was performed in accordance with OECD Guideline 310. The test item “Harpin-ab Fermentation Extract” was considered readily biodegradable under aerobic conditions.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information