Indole

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Guideline:

other: no guideline mentioned in the article

Deviations:

not specified

Principles of method if other than guideline:

Thes investigated teh biotransforamtion of indole by a microbial consortium present in anaerobically digested sludge. Indole was completely biodegraded in 10 days under methanogenic conditions using a 9% anaerobic sewage sludge inoculum forming oxindole as an intermediate metabolite; Please see culture conditions, and analysis in the attached article.

GLP compliance:

not specified

Oxygen conditions:

anaerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Municipal (State College, Pa) sewage sludge was collected from primary anaerobic digesters filtered through cheesecloth, and mixed at a ratio of 1:11 with mineral salt medium.

Initial conc.:

ca. 50 other: microgram/ml

Based on:

test mat.

Remarks:

Indole

Preliminary study:

It was not specified.

Key result

Parameter:

% degradation (test mat. analysis)

Value:

>= 100

Sampling time:

10 d

Details on results:

It is readily biodegradable.

Validity criteria fulfilled:

not specified

Interpretation of results:

readily biodegradable

Conclusions:

Indole was completely biodegraded in 10 days under methanogenic conditions using a 9% anaerobic sewage sludge inoculum forming oxindole as an intermediate metabolite; the concetration of indole in the sterile control over this time remained unchanged(1)[(1) Berry DF et al; Appl Environ Microbiol 53: 180-82 (1987)

Executive summary:

Indole was completely biodegraded in 10 days under methanogenic conditions using a 9% anaerobic sewage sludge inoculum forming oxindole as an intermediate metabolite; the concetration of indole in the sterile control over this time remained unchanged(1)[(1) Berry DF et al; Appl Environ Microbiol 53: 180-82 (1987) The methane produced (net amunt) indicated nearly complete mineralisation.

Description of key information

Indole was completely biodegraded in 10 days under methanogenic conditions using a 9% anaerobic sewage sludge inoculum forming oxindole as an intermediate metabolite; the concn of indole in the sterile control over this time remained unchanged(1).

Throughout the incubation period, net methane production increased, indicating thatindolewas mineralized(1). Complete metabolism ofindoleby methanogenic sediments from the shore, edge, and bottom of Buffalo Run stream, PA, occurred within 33 days. Asindoledisappeared, stoichiometric amounts of oxindole appeared in the sediment suspensions and persisted for over 4 weeks and was completely eliminated over 110 days(2). Complete biodegradation ofindolewas reported in 24 days using a 9% digested sludge inoculum at 22 deg C under methanogenic conditions(2).Indolewas completely biodegraded by suspensions of an organic soil (Carlisle muck) under methanogenic conditions within 67 days; concurrently, oxindole appeared, and persisted in near stoichiometric amounts for about 3 weeks(2). No oxindole accumulated under denitrifying conditions, using a soil inoculum, during the 144 days which were required forindoleto disappear(2). This pattern was again seen using a 9% sewage sludge inoculum under methanogenic and denitrifying conditions; both conditions required 7 days for complete disappearance ofindole; however, oxindole accumulated temporarily in the methanogenic culture but was not seen in the denitrifying culture probably due to rapid metabolism of this compound(2).

[(1) Berry DF et al; Appl Environ Microbiol 53: 180-82 (1987)

(2) Madsen EL et al; Appl Environ Microbiol 54: 74-78 (1988)] **PEER REVIEWED**

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable