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

Endpoint summary

Additional information

L-Threonine mother liquor represents a complex mixture containing polycyclic aromatic hydrocarbons, Al, Sb, As, Ba, Be, B, Pb, Cd, Cr, Fe, Co, Cu, Mn, Ni, Hg, Se, Ag, Tl, V, Zn, Sn, fluorides, ammonium ions, chlorides, cyanides, nitrites, phosphates, and sulphates in various amounts. L-Threonine mother liquor is a dark brown, viscous liquid with a characteristic odour and a dark brown powder after drying. In a study conducted according to guidelines (EU Method A.1, OECD Guideline 102, DIN 51004 (1994), and DIN 51007) no melting point or melting range could be determined. During the DSC measurements, a first endothermic effect was observed in the range of 120 -245°C with a broad shape and undefined onset. A second endothermic effect was found in the temperature range of 245 -330°C with a broad shape and undefined onset. The test item appeared melted and dark-brown discoloured after the measurements. At approx. 150°C the test item showed a brown discolouration and at 179 -182°C a phase change (melting) started which was accompanied by gas formation probably caused by degassing, evaporation and/or decomposition. According to REACH Regulation (Annex VII, 7.3, column II), the study on the boiling point does not need to be done for substances which decompose before boiling. In the frame of the study on the melting point, the instability of the test item was demonstrated. Therefore, a boiling point does not need to be determined. In a study conducted according to guidelines, the relative density at 21°C compared to water at 4°C was determined to be D(21/4)=1.44. According to REACH Regulation (Annex VII, 7.14, column II), the study on granulometry does not need to be conducted if the substance is marketed or used in a non granular or non solid form. L-Threonine mother liquor is marketed and used solely as aqueous solution. The vapour pressure of Biofert Plusz (read across substance) was investigated in a study conducted according to OECD Guideline 104 (Vapour Pressure Curve) and EU Method A.4 (Vapour Pressure). The vapour pressure was measured in the temperature range of 21°C to 97°C using the vapour pressure balance (effusion method). Above 52°C a vapour pressure could be measured. Therefore the values for 20 (p=3.5 x 10E-6 hPa), 25 (6.1 x 10E-6 hPa), and 50°C (7.5 x 10E-3) were calculated using the Antoine equation. Due to the inhomogenous consistency of the substance it is reasonable to specify the vapour pressure at 20°C with <3 x 10E-5 hPa. Based on the composition of Biofert Plusz this vapour pressure applies likewise to the test material under investigation (L-threonine mother liquor). According to REACH Regulation (Annex XI.2) testing of a specific endpoint may be omitted, if it is technically not possible. The determination of the partition coefficient is not applicable for complex mixtures (UVCB-substance). The log Kow of the lead component L-threonine is calclulated to be -2.94. The determination of the water solubility according to EU Method A.6 and OECD Guideline 105 was not successful due to the fact that L-threonine mother liquor has a complex compostion with individual water solubilities of the separate components. Therefore, the equilibrium method according to REACH Chapter R.7a was used. Based on the results of the preliminary tests a stirring time of 3 d and batch sizes with the threefold and fivefold amount of the evaluated water solubility was chosen. In the equilibration study the water solubility of the test item was determined to be 396 (initial weight: 40.1 g/50 mL) and 490 g/L (initial weight: 67.3 g/50 mL) at 20°C dependent on the amount of the test item added. The amount of the water insoluble fraction of the test item was determined to be 406 and 856 g/L, respectively. The surface tension of L-threonine mother liquor (dried) was determined in a study conducted according to EU Method A.5 and OECD Guideline 115. The surface tension of the test item was determined to be 44.2 mN/m at 20°C and based on this result the test item has surface active properties. According to REACH Regulation (Annex XI, 1.), a study on the flash point does not need to be done if based on the available information the substance can be assessed. L-Threonine is a solid after drying. The relevant endpoint is therefore the flammability and not the flash point. Consequently, an experimental determination of the flash point is deemed unnecessary. The relative auto-ignition temperature of the test item was investigated in a study conducted according to VDI 2263, sheet 1 and comparable to EU Method A.16. At 270°C an exothermic effect started. Due to this effect the test item temperature exceeded the temperature at 300°C (self-ignition temperature). The test item temperature rose to a maximum temperature of >850°C. According to UN transport classification and GHS/CLP, the test item must not be classified as a self-heating substance. In a study conducted according to EU Method A.10 the test item could not be ignited with a flame. Based on this result, the test item is classified as not highly flammable. According to REACH Regulation (Annex XI, 1.), experimental studies on explosiveness and oxidising potential do not need to be done if, based on the available information, the substance can be assessed. The read across substance Biofert Plusz is an aqueous suspension containing 5.1 % L-threonine, 71.9 % water and bacterial biomass and residual fermentation nutrients. Exhibiting a self-ignition temperature of > 405 °C, the substance could not be ignited with a flame. Based on the available information the substance is considered to be not explosive. Biofert Plusz is also considered to have no oxidising properties, taking into account the available information on physico-chemical properties. As L-threonine mother liquor is a component of Biofert Plusz these statements apply likewise to the test item. According to REACH Regulation (Annex IX, 7.15, column 1), a study for this endpoint is only required, if the stability in organic solvents is considered to be critical. For an aqueous solution like the UVCB-substance L-threonine mother liquor, this endpoint is neither considered to be critical nor is an experimental study technically feasible. In a study conducted according to STN 83 8305 "Prüfung der gefährlichen Eigenschaften des Abfalls, Fähigkeit der Stoffe oder des Abfalls beim Kontakt mit Wasser oder mit Luft giftige Gase in Freiheit zu setzen, Kaustizität und Korrodierbarkeit" it was found that L-threonine mother liquor is not dangerous in respect to corrosivity (corrosivity of test item: 3.05 mm/year; limit value: >6.35 mm/year) according to the regulations of the Slovak Republic. The thermal stability of L-threonine mother liquor (dried) was investigated in a study conducted according to OECD Guideline 113 via Differential Scanning colourimetry (DSC). In the frame of melting point determination a phase change in the temperature range of approx. 179 -182°C was observed. The phase change was overlaid by gas formation and brown discolouration, possibly caused by degassing, evaporation and or decomposition. The pH of the undiluted test material was determined to be 5.73. According to REACH Regulation (Annex XI, 2.) testing of a specific endpoint may be omitted, if it is technically not possible. The determination of the dissociation constant is not applicable for complex mixtures like L-threonine mother liquor (UVCB-substance). In accordance with the REACH Regulation (Annex XI, 2.), a study does not need to be done if testing is technically not feasible. The study on viscosity (information requirement section 7.17) cannot be conducted on solid materials or gases. According to ECHA Chapter 7 guidance, viscosity measurement is only relevant to liquids. L-Threonine mother liquor is a solid after drying.