Xanthan lyase

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

17 µg/L

Assessment factor:

1 000

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

170 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

1.7 µg/L

Assessment factor:

10 000

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

65 000 µg/L

Assessment factor:

1

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

no exposure of sediment expected

Sediment (marine water)

Hazard assessment conclusion:

no exposure of sediment expected

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

2.033 µg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

The aquatic toxicity data were obtained from short term toxicity studies in species representing two trophic levels (algae and crustacean).

The toxicity of Xanthan lyase, batch PPE55581 was tested in crustacean (Daphnia magna) in concentrations up to 100 mg aep/L, equivalent to 1761.4 mg enzyme concentrate dry matter/L. The No Observed Effect Concentration (NOEC) was the highest concentration tested, 1761.4 mg enzyme concentrate dry matter/L (equivalent to 100 mg aep/L).

Xanthan lyase, batch PPE55581 was tested with Pseudokirchneriella subcapitata. 72-hr ErC50 was 17 mg aep/L, equivalent to 299.4 mg enzyme concentrate dry matter/L.

Inhibition control carried out with non-proteolytic enzymes in the test of ready biodegradability showed no inhibition of the activated sludge inoculum at an enzyme concentration above the expected levels in inlet to sewage treatment plants (STPs). Monitoring of enzymes in the inlet to municipal STPs (in Denmark) resulted in concentrations of less than 2 µg active enzyme protein (aep)/L which are below the initial concentration used in tests for ready biodegradability, where no inhibitory effects were observed. It is concluded that a study on activated sludge respiration inhibition does not need to be conducted. Therefore, the test enzyme is not considered to be toxic to microorganisms.

The EC50 for xanthan lyase was 95.7 mg active enzyme protein/L was used for PNEC derivation and the assessment factors 1000 and 10000 were applied for fresh and marine water, respectively.

The PNEC value for STP is based on actual measurements of enzyme concentration in STP connected to manufacturing site. Up to 65000 µg aep/L were detected in STP connected to manufacturing site and since there was no negative impact observed, this concentration is the estimated PNEC value for STP.

PNEC values for sediment exposure have not been derived because the enzyme is readily biodegradable, highly water soluble and has a very low potential for adsorption to sediments. Exposure of the sediment to toxicologically significant concentrations of the enzyme is thus not expected.

As no soil ecotoxicity data are available for the test enzyme, the PNEC for soil is based on the PNEC for surface water using the equilibrium partitioning method. PNEC soil was estimated to 2.033 µg active enzyme protein/kg soil ww.

The enzyme is not expected to cause any significant secondary poisoning as it is ready biodegradable and has no bioaccumulation potential. Furthermore, as the test enzyme is a protein it is expected to be degraded in the gastrointestinal tract. Thus, PNEC oral is not relevant.

Conclusion on classification

Based on the aquatic toxicity studies and the ready biodegradation of the enzyme, the enzyme is not classified.