Short Chain Fructo Oligosaccharides

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:

31 August 2021 - 30 September 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

1992

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identification: Actilight 950P Premium "Fructo-Oligosaccharides"
Substance: Short-chain fructo-oligosaccharides
EC No.: 908-300-1
Appearance: White powder
Purity: 95.4%

COMPOSITION:
scFOS is short chains of fructose molecules linked to a molecule of sucrose (glucose-fructose disaccharide). Thus, scFOS is a multiconstituent substance composed of three oligosaccharides: 1-kestose (GF2), nystose (GF3) and fructosyl-nystose (GF4).
With:
- TOTAL FOS: 95.4 expressed as dry matter
- Kestose (GF2): 39.2% FOS
- Nystose (GF3): 47.6% FOS
- 1F-Fructofuranosylnystose (GF4:) 13.6% FOS
- Glucose +Fructose + Saccharose : 4.6% expressed as dry matter

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of activated sludge: municipal sewage treatment plant 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
- Storage conditions: Freshly obtained sludge was kept under continuous aeration until further treatment.
- Preparation of inoculum for exposure: Before use, sludge was coarsely sieved (1 mm2 mesh) and homogenized using a blender on medium speed for approximately 1 minute.
- Concentration of suspended solids: After treatment, concentration of suspended solids (SS) was determined to be 3.9 g/L in concentrated sludge as used for the test. Magnetically stirred sludge was used as inoculum at an amount of 2.3 mL per liter of mineral medium, leading to a SS concentration of 9 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

12 mg/L

Based on:

TOC

Initial conc.:

29.5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium according to OECD 301, prepared with Mili-RO water (tap-water purified by reverse osmosis)
- Test temperature: 22 - 23 °C
- pH: 7.6 (at test start); 7.8-7.9 (at day 14); 7.5 (at day 28)
- pH adjusted: no
- Aeration of dilution water: continuous
- Suspended solids concentration: 9 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 2-L amber glass bottles
- Number of culture flasks/concentration: 2 for test item, 2 for inoculum blank, 1 for procedural control, 1 for toxicity control
- Method used to create aerobic conditions: overnight aeration of medium and inoculum with synthetic air (20% oxygen, 80% nitrogen)
- Measuring equipment: CO2-absorbers with barium hydroxide, titration of remaining barium hydroxide to determine the produced CO2.

MEASUREMENT
- Sampling frequency: titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until day 29 (inoculum blank and test item); during at least 14 days (procedural and toxicity control).

CONTROL AND BLANK SYSTEM
- Inoculum blank: containing only inoculum
- Procedural control: containing procedural control item (sodium acetate) and inoculum
- Toxicity control: containing test item, procedural control item and inoculum

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

71

Sampling time:

28 d

Remarks on result:

other: mean of 2 vessels

Details on results:

Relative biodegradation values calculated from measurements performed during the test period revealed 80% and 63% biodegradation of the test item, for vessel A and B, respectively (based on ThCO2), mean of 71%. Since the test item consists of a mixture of structurally similar molecules, the 10-day window was not applicable.

In the toxicity control, more than 25% biodegradation occurred within 14 days (43% on Day 12, based on ThCO2). Therefore, the test item was considered not to inhibit microbial activity.

Functioning of the test system was checked by testing the procedural control item sodium acetate, which showed a normal biodegradation curve (71% within 14 days).

Validity criteria according to OECD 301B (1992):
1. The procedural control item was biodegraded by at least 60 % (actual result: 71 %) within 14 days.
2. Difference between duplicate values for %-degradation at the end of the study was less than 20 % (actual result: 18 %).
3. Total CO2 release in the blank at the end of the test did not exceed 40 mg/L (71.0 mg CO2 per 2 liters of medium, corresponding to 35.5 mg CO2/L).
4. Inorganic Carbon content (IC) of the test item (suspension) in mineral medium at the beginning of the test was less than 5 % of the Total Carbon content (TC). Since the test medium was prepared in tap-water purified by reverse osmosis (Milli- RO water (Millipore Corp., Bedford, Mass., USA, carbon levels < 500 ppb)), IC was less than 5 % of TC (mainly coming from the test item, 12 mg TOC/L).
The study met all validity criteria and is considered to be valid.

On nominal Day 14 the aeration of the toxicity control was impaired and the three gas scrubbing bottles were empty. The empty gas scrubbing bottles were caused by an error in the aeration; the wrong end of the trapping train was connected to the air supply. Since the pass level (>25 % biodegradation) was already passed before Day 14, the ability to assess potentially inhibitory effects was not impacted. Therefore, this deviation did not impact the outcome or validity of the study.

Table 1: Comparison of biodegradation (%) of test item in vessels A and B

Day	Vessel A	Vessel B	Mean A and B	Difference A-B (1)
3	12	11	12	1
5	33	27	30	6
8	58	32	45	26
12	71	53	62	19
15	74	55	65	19
19	77	60	69	17
23	78	63	70	15
29 (2)	79	63	71	17
29 (2)	79	63	71	17
29 (2)	80	63	71	18

(1): Absolute difference in biodegradation between vessels A and B

(2): Biodegradation is ended on Day 28 by addition of concentrated HCl. Therefore, differences observed on Day 29 are actually differences of Day 28.

 

Table 2: Biodegradation (%) in procedural control and toxicity control

Day	Biodegradation Procedural control (%)	Biodegradation toxicity control (%)
3	26	10
5	46	20
8	62	33
12	69	43
15 (1)	71

(1): CO2 measured on Day 15 is actually part of CO2 production of Day 14, since microbial activity was ended on Day 14 by addition of concentrated HCl.

Validity criteria fulfilled:

yes

Remarks:

See 'Details on results' for details on validity criteria

Interpretation of results:

readily biodegradable

Conclusions:

Since the test item consists of a mixture of structurally similar molecules, the 10-day window was not applicable. Fructo-oligosaccharides was readily biodegradable under the conditions of the modified Sturm test (OECD 301B, 1992).

Executive summary:

The ultimate aerobic biodegradability of the ScFOS was investigated in a GLP-compliant ready biodegradability screening study performed in accordance with OECD Guideline No. 301B.

In this test, ScFOS Micro-organisms in activated sludge were exposed to 29.5 mg/L, corresponding to 12 mg TOC/L. Several controls were carried out; Blank inoculum control, procedural control (procedural control item i.e. Sodium acetate) and toxicity control (test item and procedural control item). In the same way, 2 replicates for the test item vessels and blank inoculum control, 1 replicate each for the procedural control and toxicity control. The test duration was 28 days for the test item treatment and inoculum blank and 14 days for the procedural control and toxicity control.

As a results, relative biodegradation values calculated from measurements performed during the test period revealed 80 % and 63 % biodegradation of the test item, for vessel A and B, respectively (based on ThCO2). Since the test item consists of a mixture of structurally similar molecules, the 10-day window was not applicable.

In the toxicity control, more than 25 % biodegradation occurred within 14 days (43 % on Day 12, based on ThCO2). Therefore, the test item was considered not to inhibit microbial activity.

In conclusion, ScFOS was readily biodegradable under the conditions of the modified Sturm test. Since the test item consists of a mixture of structurally similar molecules, the 10-day window was not applicable.

Description of key information

The ultimate aerobic biodegradability of the ScFOS was investigated in a GLP-compliant ready biodegradability screening study performed in accordance with OECD Guideline No. 301B.

Under the conditions of the modified Sturm test, ScFOS was readily biodegradable and was considered not to inhibit microbial activity. Since the test item consists of a mixture of structurally similar molecules, the 10-day window was not applicable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The ready biodegradability of the ScFOS was investigated in one GLP-compliant study performed in accordance with OECD Guideline No. 301B, without deviations. The study is considered as reliable (Klimisch 1) and is selected as a key study for the endpoint.