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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

In a cell growth inhibition test using cultures of Pseudomonas putida, EC50 and EC10 for butyric acid were determined to be 78 and 51 mg/L respectively.

Key value for chemical safety assessment

EC50 for microorganisms:
78 mg/L
EC10 or NOEC for microorganisms:
51 mg/L

Additional information

The toxicity of butyric acid to microorganisms was tested in six tests. Only two of them are valid. Organisms used are Pseudomonas putida (Hüls, 1996) and Tetrahymena pyriformis (Schultz, 1997). As conservative approach, the study with the lower EC50 is selected as key study (Hüls, 1996).


Hüls 1996, key study


The growth inhibition effect of butyric acid on the bacteria Pseudomonas putida was determined according to the method of Bringmann and Kuehn. Four concentrations ranging from 12 to 100 mg/L were tested in a replicate experiment. Test preparations were incubated at 22°C for 18 hours and bacterial growth was determined measuring the turbidity of the test solution (extinction coefficient at 436 nm).


The EC50 of butyric acid was determined to be 78 mg/L.

The EC10 of butyric acid was determined to be 51 mg/L (Hüls, 1996)


Schultz 1997


In a valid 40 hour growth inhibition study, test cultures of the cilliate Tetrahymena pyriformis were exposed to butyric acid at five graduate concentrations under static conditions (individual concentrations not reported). The assay was performed in three independent replicate runs based on a preceding range finding test.


The EC50 (IGC50) value based on cell density was determined to be 329 mg/L indicating low to moderate toxicity of butyric acid to aqueous microorganisms (cilliates) (Schultz, 2006).