Supernatant from the crystallisation of L-threonine from the broth filtrate from the fermentative production of L-threonine

Endpoint summary

Additional information

Gene mutagenic activity in bacterial cells was tested in the Ames test. The study followed the OECD guideline 471 (adopted 1997). The assay was performed in two independent experiments both with and without liver microsomal activation system in S. typhimurium TA 1535, TA 100, TA 1537, TA 98 and E. coli WP2uvrA. In experiment I, concentrations of 3 - 5000 ug/plate were used and in experiment II, the concentrations were 156 - 5000 ug/plate (related to dry mass). The plates incubated showed normal background growth up to 5000 ug/plate with and without metabolic activation. No substantial increase in revertant colonies in any of the five tester strains was observed. Appropriate positive controls showed a distinct increase of induced revertant colonies. Due to the results obtained, Biofert Plusz is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.

The mutagenic properties were also tested in the mouse lymphoma assay using the cell line L5178Y both in the absence and presence of metabolic activation. The study was performed according to OECD Guideline 476 (adopted 1997) with two independent experiments, using two parallel cultures each. Concentrations based on total mass in Experiment I (4 hour treatment with and without S9 mix) and in Experiment II (24 hour treatment without S9 mix) were 39 – 1250 ug/mL (related to dry mass). No substantial and reproducible dose-dependent increase in mutant colony numbers was observed. Appropriate reference mutagens were used as positive controls and showed a distinct increase in induced mutant colonies indicating that the tests were sensitive and valid.

Biofert Plusz was tested an in vitro mammalian chromosome aberration test (GLP study according to OECD guideline 473; adopted 1997) with primary cultures of human lymphocytes both with and without metabolic activation at concentrations of 9 – 1405 ug/mL (related to dry mass). The exposure duration was 4 (Experiment I) or 22 h (Experiment II). Cultures were harvested 22 h after beginning of the treatment and three hours before harvesting, colcemid was added. Two cultures were studied for each concentration in Experiments I and II. For each culture 100 metaphases were evaluated (200 per concentration). The mitotic index was calculated from at least 1000 cells per culture. Solvent controls and positive controls were valid. The test substance did not induce structural chromosomal aberrations at dose levels up to and above precipitating concentrations.

Short description of key information:
For L-threonine mother liquor itself there are no studies available. Therefore, data for the read-across substance Biofert Plusz are taken into further consideration.

Biofert Plusz did not induce gene mutations in S. typhimurium TA 1535, TA 100, TA 1537, TA 98 and E. coli WP2uvrA with and without metabolic activation at concentrations up to 5 mg/plate (related to dry mass).
Biofert Plusz was not mutagenic in the mouse lymphoma assay using the cell line L5178Y in the absence and presence of metabolic activation and concentrations up to and above the precipitation threshold of 2225 µg/mL (total mass corresponding to 625 µg/mL dry mass).
Biofert Plusz did not induce structurai chromosomal aberrations in human Iymphocytes in vitro when tested with and without metabolic activation at dose levels up to and above precipitating concentrations (varying between 174 and 533 µg/mL related to total mass).

Endpoint Conclusion: No adverse effect observed (negative)