N-glycyl-L-tyrosine

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

not required

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
Weighed amounts of test material was added to amber colored test vessels containing 200 mL Milli-RO. The test material – Milli-RO water mixtures were magnetically stirred for a short period. Subsequently, 16 mL synthetic medium, made up to 50 mL with Milli-RO water, and 250 mL sludge were added, resulting in the required concentrations.
- Test concentration separation factor: combined limit/range-finding test

Test organisms (species):

activated sludge

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Municipal sewage treatment plant: 'Waterschap Aa en Maas', 's- Hertogenbosch, The Netherlands, receiving predominantly domestic sewage
- Preparation of inoculum for exposure:
The sludge was coarsely sieved (1 mm) and allowed to settle. The sludge was allowed to settle again for 28 minutes. The supernatant was removed and ISO-medium was added twice.
The concentration of the suspended solids was determined. The batch of sludge was used one day after collection. Therefore, 50 mL of synthetic medium was added per liter of activated
sludge at the end of the collection day. The sludge was kept aerated at test temperature until use.
- Initial biomass concentration: The concentration of suspended solids was 3.15 g/L.

Test type:

static

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20-21°C

pH:

7.1 - 8.4

Nominal and measured concentrations:

Limit test: 3 replicates at 1150 mg N-Glycyl-L-tyrosine dihydrate/L corresponding to 1000 mg N-Glycyl-L-tyrosine/L (nominal)

Range finding: 1 replicate at 11.5 and 115 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: glass vessels
- Type (delete if not applicable): open
- Aeration: yes, clean, oil-free air; The aeration will be adjusted in such a way that the dissolved
oxygen concentration at the start is above 60-70% saturation (60% of air saturation is > 5 mg/L at 20°C) and to maintain the sludge flocs in suspension.
- No. of vessels per concentration (replicates): 3 replicates at 1150 mg/L, 1 replicate at 11.5 and 115 mg/L
- No. of vessels per control (replicates): 6
- No. of vessels per abiotic control (replicates): 1
- Sludge concentration (weight of dry solids per volume): 1.575 g suspended solids/L in the final test mixture
- Nitrification inhibitor used (delete if not applicable): none

TEST MEDIUM / WATER PARAMETERS
- Medium:
Adjusted ISO medium, formulated using RO-water (tap-water purified by reverse osmosis; GEON Waterbehandeling, BerkelEnschot, The Netherlands) with the following composition:
CaCl2.2H2O 211.5 mg/L
MgSO4.7H2O 88.8 mg/L
NaHCO3 46.7 mg/L
KCl 4.2 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 150 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 150 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

The EC50 of 3,5-dichlorophenol was in the accepted range of 2 to 25 mg/L for total respiration (actual value: 7.4 mg/L).

The mean control oxygen uptake rate exceeded 20 mg oxygen per gram of activated sludge (dry weight of suspended solids) per hour (actual value: 40 mg O2/g∙h).
The coefficient of variation of oxygen uptake in control replicates did not exceed 30 % at the end of the test (actual value: 12 %).

The EC50 of 3,5-dichlorophenol was in the accepted range of 2 to 25 mg/L for total respiration (actual value: 7.4 mg/L).

Since all validity criteria were satisfied the study was considered to be valid.

Validity criteria fulfilled:

yes

Conclusions:

The test item was not toxic to waste water bacteria (activated sludge) at or below a concentration of 1150 mg/L corresponding to 1000 mg/L active ingredient (NOEC).

Description of key information

N-Glycyl-L-tyrosine is not toxic to waste water bacteria (activated sludge) at or below a concentration of 1000 mg/L (NOEC)

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L