Sophorolipids: fermentation products of glucose and fatty acids, C18 (unsaturated), glycerol esters with yeast Candida Bombicola

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-03-16 to 2016-04-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Version / remarks:

440/2008/EEC

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: Sewage treatment plant Ruhrverband Kläranlage, Schmallenberg, mainly fed with municipal wastewater
- Concentration: 29.5 mg dry mass/L

Duration of test (contact time):

28 d

Initial conc.:

60 mg/L

Based on:

test mat.

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
(a) KH2PO4: 8.5 g/L
K2HPO4: 21.75 g/L
Na2HPO4: 24.93 g/L
NH4Cl: 0.50 g/L
pH 7.4 +/- 0.2
(b) CaCl2 x 2H2O: 36.40 g/L
(c) MgSO4 x 7 H2O: 22.50 g/L
(d) FeCl3 x 6 H2O: 0.25 g/L
The mineral medium applied in the test contained 10 mL/L of mineral stock solution (a) and 1 mL/L of the mineral stock solutions (b) - (d), respectively.
- Solubilising agent (type and concentration if used): none
- Test temperature: 22 °C (+/-) 1 °C
- pH: 7.5-7.9
- pH adjusted: no
- Continuous darkness: yes
TEST SYSTEM
- Number of culture flasks/concentration: Two vessels/concentration
- Method used to create aerobic conditions: Aeration during the whole test
- Measuring equipment: SAPROMAT respirometer (VOITH Inc.)
- Test performed in closed vessels
SAMPLING
- Sampling frequency: continuous measurement of the oxygen demand using a SAPROMAT respirometer
CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: 100 mg test item/L sterilised mineral test medium (25mg/250 mL)
- Toxicity control: 100 mg test item/L and reference item at 100 mg/L mineral test medium (25 mg test item/250 mL and 25 mg reference item/250 ml)

Reference substance:

benzoic acid, sodium salt

Test performance:

The test item in concentrations of about 100 and 60 mg per litre mineral medium, respectively, and sodium benzoate in concentrations of about 100 mg per litre mineral medium, were incubated with 29.5 mg dry mass inoculum per litre mineral medium in 500 mL glass vessels at a medium volume of 250 mL. The test was run for 28 days, in darkness at 22 °C (+/-) 1 °C. The suspension was aerated during the whole test. Oxygen demand was carried out throughout the test course.

Parameter:

% degradation (O2 consumption)

Value:

69

St. dev.:

0.8

Remarks on result:

other: continous measurement

Parameter:

% degradation (O2 consumption)

Value:

85

St. dev.:

5.4

Remarks on result:

other: continous measurement

Details on results:

The biodegradation within the 10-day-window was 61 % and 75 % in the assays with 100 mg/L and 60 mg/L, respectively. The 10-day-window started at day 1 for a concentration of 60 mg/L and at day 2 for a concentration of 100 mg/L

Results with reference substance:

The degradation of the reference substance sodium benzoate had reached 83 % within the first 14 days.

The biodegradation of the test item after 28 days of incubation in the static test was found to be 69 % (SD = 0.8 %) and 85 % (SD = 5.4 %) in the assays with 100 mg/L and 60 mg/L, respectively. The biodegradation within the 10-day-window was 61 % and 75 % in the assays with 100 mg/L and 60 mg/L, respectively. The 10-day-window started at day 1 for a concentration of 60 mg test item per litre and at day 2 for a concentration of 100 mg test item per litre.

With 4 %, there was no significant abiotic degradation of the test item noticeable within the 28 days of incubation.

The biodegradation of the item mixture in the toxicity control was found to be 65 % after 14 days of incubation. Thus, the demanded threshold value of 25 % is exceeded and the test item can be identified as non-toxic in a ready biodegradability test.

The reference item sodium benzoate was degraded to 83 % within the first 14 days.

Table 1: pH values at test start. Single values of the parallel test vessels.

vessel	Inoculum blank	Test suspension A	Test suspension B	Abiotic control	Procedural control	Toxicity control
1	7.5	7.5	7.5	7.5	7.5	7.5
2	7.6	7.5	7.5	7.5	7.5	7.5

Table 2: pH values at test end. Single values of the parallel test vessels.

vessel	Inoculum blank	Test suspension A	Test suspension B	Abiotic control	Procedural control	Toxicity control
1	7.7	7.9	7.9	7.7	8.5	8.8
2	7.8	7.9	7.9	7.7	8.6	8.8

Table 3: Oxygen consumption. Cumulated consumption (mg O₂/L) after 14 days. Single and mean values of the parallel test vessels and standard deviation. Test suspension B: 60 mg/L; Test suspension A and abiotic control: 100 mg/L; Procedural control: 100 mg/L; Toxicity control: 200 mg/L.

vessel	Inoculum blank	Test suspension A	Test suspension B	Abiotic control	Procedural control	Toxicity control
1	22	76	59	0	160	189
2	23	77	67	3	161	187
Mean	23	77	63	2	161	188
SD	1	1	6	2	1	1

Table 4: Percent degradation. Degradation (%) after 14 days. Single and mean values of the parallel test vessels and standard deviation.

vessel	-	Test suspension A	Test suspension B	Abiotic control	Procedural control	Toxicity control
1	-	61.8	70.3	0.0	82.6	65.8
2	-	63.0	85.7	3.5	83.2	65.0
Mean	-	62.4	78.0	1.7	82.9	65.4
SD	-	0.8	10.9	2.5	0.4	0.6

Table 5: Per Oxygen consumption. Cumulated consumption (mg O₂/L) after 28 days. Single and mean values of the parallel test vessels and standard deviation. Test suspension B: 60 mg/L; Test suspension A and abiotic control: 100 mg/L; Procedural control: 100 mg/L; Toxicity control: 200 mg/L. cent degradation. Degradation (%) after 14 days. Single and mean values of the parallel test vessels and standard deviation.

vessel	Inoculum blank	Test suspension A	Test suspension B	Abiotic control	Procedural control	Toxicity control
1	28	88	70	0	172	204
2	28	87	74	7	174	205
Mean	28	88	72	4	173	205
SD	0	1	3	5	1	1

Table 6: Percent degradation. Degradation (%) after 28 days. Single and mean values of the parallel test vessels and standard deviation.

vessel	-	Test suspension A	Test suspension B	Abiotic control	Procedural control	Toxicity control
1	-	69.3	80.9	0.0	86.5	69.5
2	-	68.2	88.6	8.1	87.7	69.9
Mean	-	68.7	84.7	4.0	87.1	69.7
SD	-	0.8	5.4	5.7	0.8	0.3

 

 

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The biodegradation of the test substance after 28 days incubation in the static test was found to be 69 % and 85 % in the assays with 100 mg/L and 60 mg/L, respectively.

Executive summary:

The biodegradation of the test substance was investigated over a 28 day period in a manometric Respirometry Test according to OECD Guideline 301 F (1992). The test medium was inoculated with microorganisms from a digester of a sewage treatment plant mainly fed with municipal wastewater.

The rate of degradation was monitored by measuring the quantity of oxygen required to maintain a constant gas volume in the respirometer flasks over 28 days.

Sodium benzoate was used as a degradable reference substance at a concentration of 100 mg/L, along with a toxicity control at 100 mg/L test substance and 100 mg/L sodium benzoate.

The biodegradation of the test substance was found to be at mean 69 % with a standard deviation of 0.8 % for a concentration of 100 mg test substance/L and at mean 85 % with a standard deviation of 5.4 % for a concentration of 60 mg test item/L. For a concentration of 100 mg test substance/L biodegradation within the 10-day-window was found to be 61 %.

For a concentration of 60 mg test substance/L biodegradation within the 10-day-window was found to be 75 %.

The degradation of of the reference substance sodium benzoate had reached 83 % within the first 14 days.

According to the guideline, the test item is considered as being readily biodegradable under the test conditions.

Description of key information

The biodegradation of a read-across substance was investigated in tests under aerobic conditions. The source substance was found to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The biodegradability of Sophorolipids was investigated a guideline study.

OECD guideline 301F

The biodegradation of the test substance was investigated over a 28 day period in a manometric Respirometry Test according to OECD Guideline 301 F (1992). The test medium was inoculated with microorganisms from a digester of a sewage treatment plant mainly fed with municipal wastewater.

The rate of degradation was monitored by measuring the quantity of oxygen required to maintain a constant gas volume in the respirometer flasks over 28 days.

Sodium benzoate was used as a degradable reference substance at a concentration of 100 mg/L, along with a toxicity control at 100 mg/L test substance and 100 mg/L sodium benzoate. The biodegradation of the test substance was found to be at mean 69 % with a standard deviation of 0.8 % for a concentration of 100 mg test substance/L and at mean 85 % with a standard deviation of 5.4 % for a concentration of 60 mg test item/L. For a concentration of 100 mg test substance/L biodegradation within the 10-day-window was found to be 61 %.

For a concentration of 60 mg test substance/L biodegradation within the 10-day-window was found to be 75 %.

The degradation of of the reference substance sodium benzoate had reached 83 % within the first 14 days.

According to the guideline, the test item is considered as being readily biodegradable under the test conditions.