A Microbiological Method for the Quantitative Determination of 6-Aminopenicillanic Acid in Penicillin Fermentations

Abstract

Several autors have described methods for the quantitative assay of 6-aminopenicillanic acid. Kato⁽¹⁾ extracted the penicillins with an organic solvent and determined the content of 6-aminopenicillanic acid (“penicillin nucleus”) in the fermented broth from the difference between the results of the iodometric assay of the extract and the original filtrate. Levitov ⁽²⁾ determined the content of the “penicillin nucleus” from the difference between the results of the iodometric and biological assays of broths. Wolf & Arnstein⁽³⁾ extracted penicillins with an organic solvent and after acylation of the water phase microbiologically determined the content of 6-aminopenicillanic acid. Batchelor et al.⁽⁴⁾ have described a chromatographic method for the identification of 6-aminopenicillanic acid based on its reaction with phenylacetylchloride in the presence of sodium bicarbonate resulting in the formation of benzylpenicillin. These authors mentioned the possibility of a quantitative determination of 6-aminopenicillanic acid from the sizes of the zones of inhibition around the biologically detected chromatograms.

We have published a quantitative method for the assay of penicillin and other antibiotics^(5,6) which we have now adapted also for the determination of 6-aminopenicillanic acid.