Histidine

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:

weight of evidence

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Chemical oxygen demand (COD) was assessed by standard methods. The bio-chemical oxygen demand (BOD) was analysed using a Sapromat BOD measuring unit. Biological degradation-inhibition test was performed using the Offhaus method.

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

not specified

Duration of test (contact time):

5 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

50

Sampling time:

5 d

Parameter:

BOD5

Value:

517 mg O2/g test mat.

Parameter:

COD

Value:

1 023 mg O2/g test mat.

Parameter:

BOD5*100/COD

Value:

50.54 other: %

The BOD5 test showed good biological degradation. The test item was degraded 50 % after a short exposure of 5 days.

Based on the observed respiration activity, it is expected that the biodegradation should take place undisturbed, even at higher concentrations and especially after certain adaptation.

Interpretation of results:

other: biodegradable according to Offhaus method

Conclusions:

The BOD5 was determined to be 517 mg O2/g for a substance with COD = 1023 mg O2/g.
The inhibition study showed negligible inhibition (5.4%), however not decreasing.
The test shows that after 5 days 50 % of the substance has degraded, but longer testing is needed to conclude on readily biodegradability.

Executive summary:

In this study, the biochemical oxygen demand (BOD) was analysed using a Sapromat BOD measuring unit and compared to the chemical oxygen demand (COD). Biological degradation-inhibition test was performed using the Offhaus method. It is not a GLP study and no OECD guideline was followed.

After 5 days, the BOD5 was determined to be 517 mg O2/g for L-histidine (COD = 1023 mg O2/g). The test is showing good biological degradation, i.e. 50 % after 5 days.

Based on the observed respiration activity, the degradation should take place undisturbed, even at higher concentrations and especially after certain adaptation.

Reference 2

Endpoint:

biodegradation in water: screening test, other

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Qualifier:

no guideline followed

Principles of method if other than guideline:

Activated sludge was exposed to chemicals, oxygen uptake was measured during 24h using the Warburg respirometer.

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): 3 sources of activated sludge
Source 1: Columbus, Ohio, municipal treatment plant, combined domestic and industrial wastewater
Source 2: Hilliard, Ohio, municipal treatment plant, domestic wastewater
Source 3: Brookside estates, Linworth, Ohio, residential wastewater
- Storage length: sample taken from aeration tank on day experiment started
- Preparation of inoculum for exposure: sludge suspension was blended for 10 sec and 20 ml was pipetted into the Warburg flasks
- Concentration of sludge: 2500 mg/L
- Water filtered: no

Duration of test (contact time):

24 h

Initial conc.:

500 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test temperature: 20 °C

TEST SYSTEM
- Measuring equipment: Warburg respirometers, readings 0.5 to 5 h intervals

CONTROL AND BLANK SYSTEM
- Inoculum blank: control flask included with each run

Key result

Parameter:

% degradation (O2 consumption)

Value:

16.5

Sampling time:

24 h

Conclusions:

L-histidine showed good biodegradation within 24h, i.e. 16.5% of the initial test material was biodegraded within 24h. This study indicates that L-histidine has a potential to readily biodegrade.

Executive summary:

This study investigated the ability of activated sludges from 3 municipal waste treatment plants to oxidise amino acids. The activated sludge (concentration 2500 mg/L) was exposed to L-histidine at a concentration of 500 mg/L. The biodegradation was assessed during 24h by measurement of the O2 consumption using Warburg flasks.

The average biodegradation (as % of theoretical oxygen demand) over the 3 activated sludges was 16.5 %. Even though this study does not allow conclusion on ready biodegradability of L-histidine, the study clearly shows that rapid biodegradation can be expected since within 24h nearly 17 % of the substance is biodegraded.

Description of key information

The study of Mueller and Neumann (1981) assessed the biodegradability of L-histidine in a Sapromat apparatus. The test was not performed according to GLP nor internationally accepted guidelines.

At a test concentration of ca. 200 mg/L, a BOD5 of 517 mg O2/g was determined. Histidine hase a COD value of 1023 mg O2/g. The test shows good biological degradation, i.e. 50 % biodegradation after 5 days.

Based on the observed respiration activity, the degradation should take place undisturbed, even at higher concentrations and especially after certain adaptation.

A second study on the biodegradability of L-histidine is available (Malaney and Gerhold). In this study dating back to

1969, the ability of activated sludges from 3 municipal waste treatment plants to oxidise amino acids

was investigared. The activated sludge (concentration 2500 mg/L) was exposed to L-histidine at a

concentration of 500 mg/L. The biodegradation was assessed during 24h by measurement of the O2

consumption using Warburg flasks. The average biodegradation (as % of theoretical oxygen demand)

over the 3 activated sludges was 16.5 %.

The test was not performed according to GLP nor internationally accepted guidelines.