L-(+)-lactic acid

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Outdated test guideline, not fully suitable for assessing ready biodegradability according to recent standards. Publication with relatively poor documentation of methodology and test condtitions.

Qualifier:

according to guideline

Guideline:

EU Method C.5 (Degradation: Biochemical Oxygen Demand)

Version / remarks:

Cited as Directive 92/69/EEC, C.5

GLP compliance:

no

Specific details on test material used for the study:

Lactic acid obtained from PURAC.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Duration of test (contact time):

20 d

Initial conc.:

4 mg/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on results:

BOD 20 = 0.60 mg O2 per mg test substance

Parameter:

BOD5

Value:

0.45 g O2/g test mat.

Parameter:

COD

Value:

0.85 g O2/g test mat.

Parameter:

BOD5*100/COD

Value:

50

Validity criteria fulfilled:

not applicable

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

Lactic acid is considered to be readily biodegradable. In view of methodological limitations, this study is used as supportive data.

Executive summary:

The biodegradation of lactic acid and lactate esters was studied. The aim of the study was to provide predicted environmental data for additional alkyl homologues and metal salts. Lactic acid and its alkyl esters were degraded by more than 60 % in the ready biodegradability tests and from the data presented it is evident that lactic acid and the majority of alkyl lactates are readily biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

Outdated test guideline, not fully suitable for assessing ready biodegradability according to recent standards. Conduct of test valid according to guidelines applicable at that time, hence reliable with restrictions and used as supportive data.

Qualifier:

according to guideline

Guideline:

EU Method C.5 (Degradation: Biochemical Oxygen Demand)

Version / remarks:

Cited as Directive 84/449/EEC, C.8, and NEN 6634

Qualifier:

according to guideline

Guideline:

EU Method C.6 (Degradation: Chemical Oxygen Demand)

Version / remarks:

Cited as Directive 84/449/EEC, C.9, and NEN 6633

GLP compliance:

yes

Specific details on test material used for the study:

Ca. 80 % aqueous solution of lactic acid, batch no. ZO 3456

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

A sample of activated sludge was taken from an oxidation ditch situated on the premises of TNO, Delft, The Netherlands. The oxidation ditch is used to treat domestic sewage. The original sludge (containing 3.5-4.0 g of solid substance.l'l) was allowed to settle for 4-8 minutes and 2 ml of the supernatant was used to inoculate each litre of BOD dilution water (ref. 1). The dilution water was aerated vigorously before use.

Duration of test (contact time):

ca. 20 d

Initial conc.:

0 mg/L

Initial conc.:

2 mg/L

Initial conc.:

4

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The BOD determination was conducted as described in the protocol, developed mainly from the Dutch Guideline 'Water-Determination of Biochemical Oxygen Demand after n days (BODn)' (NEN 6634). Test concentrations of 2.0 and 4.0 mg/l were prepared by adding respectively 33 and 66 ml of the 199.6 mg/l stock solution to 3.3 l lots of inoculated BOD dilution water. In order to check the activity of the inoculum and the possible toxicity of the test sub- stance, l ml/l1 of a solution containing 3 g/l of glucose and 3 g/l of glutamic acid, and this mixture with 4 mg/l of L(+) lactic acid were also tested.
Nitrification control was included by adding 2.5 mg/l of allylthiourea to bottles containing 2 mg\l of L(+) lactic acid. Quadruplicate BOD bottles were incubated at 20°C for 20 days. The COD was determined with two samples of l ml from a solution of 405.7 mg of test substance in 100 ml of Milli-Q water, and conducted as detailed in the Dutch Guideline.

Reference substance:

other: Glucose

Reference substance:

other: Glutamic acid

Reference substance:

other: Allyl thiourea

Test performance:

The oxygen concentrations measured in the various bottles of the BOD determination are given in Annex B and discussed in detail in sections 3.1 and 3.2. Table l lists the mean oxygen concentrations measured and the oxygen consumption and BOD values calculated for L(-i-) lactic acid (referring to the test substance as such, containing 80 % L-(+)-lactic acid).
The pH of the medium in the BOD bottles was 7.0-7.1 at the start of the test, 6.6-6.9 after twenty days. The pH values in bottles with glucose added were generally lower 6.1-6.3. The temperatures measured in the BOD bottles varied between 19.9 and 20.7 °C.

Parameter:

% degradation (O2 consumption)

Value:

50

Sampling time:

5 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

67

Sampling time:

20 d

Details on results:

The BOD5 and BOD20 values of the various concentrations of L-(+)-lactic acid were in the ranges 0.44-0.45 mg O2/L and 0.54-0.60 mg O2/L, respectively; it was therefore concluded that the BOD5 and BOD20 of L-(+)-lactic acid are 0.45 and 0.60 mg O2/mg, respectively.
Similar oxygen consumption by the test substance was also found in the presence of glucose and glutamic acid, confirming these results. The COD value of L-(+)-lactic acid was found to be 0.902 mg O2/mg (duplicate values: 0.873 and 0.930 mg O2/mg). The theoretical oxygen demand was calculated tobe 0.85 mg O2/mg.
Comparison of the BOD and COD values indicates that degradation was about 50 % after 5 days and about 67 % after 20 days.

Parameter:

BOD5

Value:

0.45 g O2/g test mat.

Parameter:

COD

Value:

0.9 g O2/g test mat.

Parameter:

BOD5*100/COD

Value:

50

Results with reference substance:

The BOD5 and BOD20 values of the glucose/glutamic acid control were 3.02 mg O2/L and 7.29 mg O2/L respectively; these values indicate that the activity of the inoculum was not quite sufficient. According to ref. (3) a 150 mg/L glucose/glutamic acid mixture should have a BOD5 value of 200 ± 37 mg O2/L; this cor- responds to a value of 4.0 ± 0.75 mg O2/L for a 3 mg/L mixture. Since the BOD values were similar at both test substance concentrations and only slightly lower than the value found in the presence of glucose/glutamic acid with its higher microbial activity, the test was regarded as valid.
The results obtained by adding allylthiourea showed that some nitrification had taken place.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

With a BOD5 of 50 % and BOD20 of 67 % of COD, and considering the function of lactic acid in biological systems, it can be concluded that lactic acid is readily biodegradable. Since following an outdated and not fully adequate test guideline, the study is used as supportive data.

Executive summary:

BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) determinations were carried out for L-(+)-lactic acid using the method described in the Dutch guidelines 'Water – Determination of Biochemical Oxygen Demand after n days (BODn)' (NEN 6634) and 'Water – Determination of Chemical Oxygen Demand (COD)' (NEN 6633), respectively. These methods are similar to those referred to in the EC test guidelines C.5 and C.6 (Regulation (EC) No 440/2008). The study was carried out in accordance with the OECD principles of Good Laboratory Practice.

The test substance was a pure chemical with a high solubility in water. Two concentrations (2 and 4 mg/L) were tested. An inoculum was prepared from activated sludge. lts microbial activity appeared to be sufficient although the control substances glucose and glutamic acid had a BOD5 of slightly less than the required value of 4.00 ± 0.75 mg O₂/L.

No toxic effects were found. The BOD5 of L-(+)-lactic acid was 0.45 mg O₂/mg and the BOD20 was 0.60 mg O₂/mg; the COD was 0.90 mg O₂/mg. These figures indicate a degradation of 50 and 67 % after 5 and 20 days, respectively.

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

The QMRF and QPRF for the QSAR calculation are available below (see attached background material).

Qualifier:

according to guideline

Guideline:

other: REACH guidance on information requirements and chemical safety assessment, chapter R.6: QSARs and grouping of chemicals, May 2008.

Principles of method if other than guideline:

(Q)SAR calculation

GLP compliance:

no

Key result

Parameter:

other: Primary and ultimate biodegradability prediction: YES

Remarks on result:

other: QSAR calculation (BIOWIN)

Details on results:

Biowin1 (Linear Biodeg Probability) 0.9361
Biowin2 (Non-Linear Biodeg Probability) 0.9704
A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast
A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

Biowin3 (Survey Model - Ultimate Biodeg) 3.5247
Biowin4 (Survey Model - Primary Biodeg) 4.2328
Result Classification: 5.00 -> hours 4.00 -> days 3.00 -> weeks
(Primary & Ultimate) 2.00 -> months 1.00 -> longer

Biowin5 (MITI Linear Biodeg Probability) 0.7362
Biowin6 (MITI Non-Linear Biodeg Probability) 0.8791
A Probability Greater Than or Equal to 0.5 indicates --> Readily Degradable
A Probability Less Than 0.5 indicates --> NOT Readily Degradable

Biowin7 (Anaerobic Linear Biodeg Prob) 0.9102
A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast
A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

Validity criteria fulfilled:

not applicable

Interpretation of results:

readily biodegradable

Conclusions:

L-(+)-lactic acid is predicted to be readily biodegradable by the (Q)SAR model BIOWIN v4.10.

Executive summary:

L-(+)-lactic acid is predicted to be readily biodegradable by the (Q)SAR model BIOWIN v4.10.

Reference 4

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019-04-04 to 2019-07-24

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

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Purity: 80.2%
- Appearance: clear colurless liquid
- Lot no.: 1701002415
- Expiry date: 2022-01-20
- Storage: at room temperature

Oxygen conditions:

aerobic

Remarks:

Mixture of oxygen (ca. 20%) and nitrogen (ca. 80%) was passed through a bottle, containing 0.5-1 litre 0.0125 M Ba(OH)2 solution to trap CO2

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch. Freshly obtained sludge was kept under continuous aeration until use.
Magnetically stirred sludge was used as inoculum at an amount of 3 mL per litre of mineral medium, leading to a SS concentration of 9.6 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

37.5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: According to guideline
- Additional substrate: Not applicable
- Solubilising agent (type and concentration if used): None
- Test temperature: 22–23 °C
- pH: 7.6–7.8
- pH adjusted: pH was adjusted from 2.8 to 7.6 using 1 M NaOH and 1 M HCl
- Aeration of dilution water: mixture of oxygen (ca. 20%) and nitrogen (ca. 80%) was passed through a bottle, containing 0.5–1 litre 0.0125 M Ba(OH)2 solution to trap CO2 which might be present in small amounts. Synthetic air was passed through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min)
- Suspended solids concentration: 9.6 g/L
- Continuous darkness: yes through usage of brown tubes

TEST SYSTEM
- Number of culture flasks/concentration: 2 inoculum blanks, 2 test bottles, 1 procedural control, 1 toxicity control
- Method used to create aerobic conditions: synthetic air
- Measuring equipment: CO2 traps, titration
- Test performed in closed vessels due to significant volatility of test substance: No
- Test performed in open system: Yes
- Details of trap for CO2: 0.5–1 litre 0.0125 M Ba(OH)2 solution to trap CO2

SAMPLING
- Sampling frequency and method: Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until day 28, for inoculum blank and test item. Titrations for procedural and toxicity control were made over a period of at least 14 days. Phenolphthalein (1% solution in ethanol, Merck) was used as pH-indicator.
- Sample storage before analysis: room temp storage
- Sterility check if applicable: not applicable

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes: 2
- Abiotic sterile control: None
- Toxicity control: yes: 1; PURAC Sanilac 80 plus sodium acetate
- Other: 1 procedural control: sodium acetate

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

75.5

Sampling time:

28 d

Details on results:

Relative biodegradation values calculated from measurements performed during the test period revealed 75 and 76 % biodegradation of PURAC Sanilac 80, for vessel A and B, respectively (based on ThCO2).

Validity criteria fulfilled:

yes

Remarks:

All criteria for acceptability of the test were met: 92 % of procedural control item was biodegraded within 14 days; difference between duplicated values: 2%; total CO2 release in blank did not exceed 40 mg/L (value was 31.2 mg CO2/L)

Interpretation of results:

readily biodegradable

Conclusions:

In an OECD 301B study, L-(+)-lactic acid proved to be readily biodegradable.

Executive summary:

The biodegradation of lactic acid was studied. The aim of this study was to provide data on the degradation time scale of the lactic acid, in the presence of activated sludge as inoculum, folliwing the guideline of OECD 301B. Relative biodegradation values calculated from measurements performed during the test period revealed 75 % biodegradation of PURAC Sanilac 80 (based on ThCO2). 
In the toxicity control, PURAC Sanilac 80 was found not to inhibit microbial activity.
In conclusion, PURAC Sanilac 80 is considered readily biodegradable. 

Description of key information

L-lactic acid is considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

L-(+)-lactic acid has proven as readily biodegradable in a test according to OECD guideline 301B. This is additionally supported by the validated QSAR model BIOWIN v4.10 and supportive experimental studies (BOD5 and COD measurements) not satisfying recent standards for ready biodegradability tests. Overall, the available data allow the unequivocal conclusion, that L-(+)-lactic acid is readily biodegradable.