Saccharomyces cerevisiae cell wall, extracted

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Based on the following available in vitro key studies, the test substance Saccharomyces cerevisiae cell walls, extracted is not genotoxic:

- In vitro gene mutation study in bacteria (Ames test) (Toth Gonczol, OECD TG 471, GLP, 2020, Klimisch 1): negative with and without metabolic activation

- In vitro Mammalian Cell Micronucleus study (Kovacs, OECD 487, GLP, 2020, Klimisch 1): negative with and without metabolic activation.

- Read across from Saccharomyces cerevisiae, lysate In vitro Mammalian Cell Gene Mutation Test (Sire, OECD 490, GLP, 2018, Klimisch 1): negative with and without metabolic activation

Hence, according to the CLP criteria, the test substance was not classified for genetic toxicity.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

Waiving (see additional information).

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

A GLP Ames study is available on the target substance Saccharomyces cerevisiae cell walls, extracted (Toth Gonczol, OECD TG 471, GLP, 2020, Klimisch 1). It was performed on the following bacterial strains: TA98, 100, 1535, 1537 and E. Coli WP2 uvrA. Bacteria were exposed with and without metabolic activation to different concentrations up to 500 µg/plate and the number of revertant colonies was counted. No increase in the revertant colony number was observed in any of the experimental conditions. Based on the results of this study, Saccharomyces cerevisiae cell walls, extracted was not considered to be mutagenic in a bacterial reverse mutation test.

A GLP In vitro Mammalian Cell Micronucleus study is available on the target substance Saccharomyces cerevisiae cell walls, extracted (Kovacs, OECD 487, GLP, 2020, Klimisch 1). It was performed using mouse lymphoma L5178Y TK+/-3.7.2 C cells. Concentrations of 200, 100 and 33.3 µg/mL were chosen for evaluation in case of the short treatment with metabolic activation, concentrations of 100, 3.33 and 11.1 µg/mL were chosen for evaluation in case of the short treatment without metabolic activation and concentrations of 200, 100 and 33.3 µg/mL were chosen for evaluation in case of the long treatment without metabolic activation. None of the treatment concentrations caused a biologically or statistically significant increase in the number of micronucleated cells when compared to the appropriate negative (vehicle) control value in the experiments with and without metabolic activation. Based on the results of this study, Saccharomyces cerevisiae cell wall, extracted was considered as not being genotoxic in this test system.

No in vitro gene mutation in mammalian cells study is available on the target substance Saccharomyces cerevisiae cell walls, extracted. However, data are available on an analogue substance Saccharomyces cerevisiae, lysate and a read across approach was used to fulfill data requirement for this endpoint.

The read across approach is based on the following similarities between the target substance “Saccharomyces cerevisiae cell wall, extracted”, EC 949-711-6 and the source substance “Saccharomyces cerevisiae, lysate”, EC 305-230-8:

-The same raw material, biological organisms and fermentation process,

- Common steps to recover the yeast and to lyse them,

- Only the last step, following the lysis of the cells, is different with for “Saccharomyces cerevisiae cell wall, extracted”, cell walls are recovered, whereas for the lysates, both cellular extracts and cell walls are recovered (i.e. soluble and insoluble fractions resulting from the cell lysis are recovered together).

Consequently, from the process, it can be concluded that “Saccharomyces cerevisiae cell wall, extracted” is constituted mainly by the insoluble fraction of the lysates and by a negligible soluble fraction of the lysates.

The specifications of “Saccharomyces cerevisiae cell wall, extracted” are the following:

-       > 70% to 99% for the insoluble fraction,

-       1% to 30% for the soluble fraction.    

Thus, Cell walls are a part of the lysate. When performing toxicological tests with the source substance, concentrations of soluble constituents in the soluble fraction are higher than those of the target substance which contains a far lower soluble fraction. In addition, analyses were performed which demonstrated that the composition of the soluble fraction of target “Saccharomyces cerevisiae cell wall, extracted” is close to the composition of the source substance “Saccharomyces cerevisiae, lysate”. Consequently, the results of the toxicological tests performed on the yeast lysate can reasonably be considered as a worst-case approach to assess the toxicity to human health of the yeast cell walls.

Finally, the comparison between toxicological data generated on the target substance and the data available on the analogue source substance showed that the results are much the same (consistent), which further reinforces the read across justification.

A GLP in vitro gene mutation in mammalian cells test was performed on substance Saccharomyces cerevisiae, lysate (SIRE, OECD TG 490, GLP, 2018, Klimisch 1). L5178Y TK+/- mouse lymphoma cells were exposed to dose levels of 3.13, 6.25, 12.5, 25, 50 and 100 μg/mL for each experiment with or without S9 mix. Following the 3-hour treatments with and without S9 mix or the 24-hour treatment without S9 mix, no increase in the mutation frequency exceeding the GEF was observed at any of the tested dose levels relative to the corresponding vehicle control. Moreover, no dose-response relationship was demonstrated by the linear regression in any test conditions. These results did not meet the criteria for a positive response. Under the experimental conditions of this study, the test item, Saccharomyces cerevisiae, lysate, did not show any mutagenic activity in the mouse lymphoma assay, either in the presence or absence of a rat liver metabolizing system.

Reliable experimental data for mutagenicity on bacteria as well as In vitro Mammalian Cell Micronucleus test are also available on the analogue substance Saccharomyces cerevisiae, lysate (not reported in the current dossier but available in the REACh disseminated dossier of Saccharomyces cerevisiae, lysate). Both tests gave also negative results and further reinforces the read across justification.

According to Regulation (EC) No 1907/2006, Annex IX, 8.4, column 2, if there is a positive result in any of the in vitro genotoxicity studies in Annex VII or VIII and there are no results available from an in vivo study already, an appropriate in vivo somatic cell genotoxicity study shall be proposed by the registrant.

Based on the negative results obtained in all three in vitro genotoxicity studies from Annex VII or VIII with the target substance Saccharomyces cerevisiae cell wall, extracted (Toth Gonczol, OECD TG 471, GLP, 2020, Klimisch 1; Kovacs, OECD 487, GLP, 2020, Klimisch 1) or on its structurally related analogue Saccharomyces cerevisiae, lysate (Sire, Klimisch 1, GLP, 2018, OECD TG 490), an in vivo somatic cell genotoxicity study need not to be proposed.

Justification for classification or non-classification

The target substance was negative in a bacterial reverse mutation test and In vitro Mammalian Cell Micronucleus. A read across in vitro gene mutation in mammalian cells test also gave negative results. Based on these results, the substance is not considered to meet the criteria for classification according to the CLP regulation criteria.