6-Aminopenicillanic acid. I. 6-Aminopenicillanic acid in penicillin fermentations

Effect of media composition on the penicillin production

The conventional penicillin fermentation medium is composed of corn steep liquor, glucose, lactose, minerals, oil, and precursor. The penicillin activity was not affected, due to the addition of carbonate 0-1% or whale oil 0.5% instead of 1%. Also the omission of cupric, magnesium, manganese, zinc sulphates, and acetic acid did not affect the penicillin activity, while the omission of ammonium nitrate and potassium dihydrogen phosphate decreased the penicillin activity in the medium. The penicillin activity of a medium containing 2% calcium superphosphate was higher than that of the control medium, containing 0.4% potassium dihydrogen phosphate and 1% calcium carbonate. Instead of adding the precursor twice, after 0 and 48 hrs, the addition of phenylacetamide in the amount of 0.2%, at the start, did not affect the activity, while addition of phenylacetic acid (0.2%), at the start, decreased the penicillin activity. The omission of the precursors in the medium decreased the penicillin activity measured microbiologically, however, 6-aminopenicillanic acid content was relatively higher as compared with that of the control medium, containing precursor. These results were confirmed, using iodometric assay and paper chromatographic analysis.

6-Aminopenicillanic acid. VI. Formation of 6-aminopenicillanic acid from penicillin by enzymic hydrolysis

Penicillin amidase activity, resulting in the hydrolysis of phenoxymethylpenicillin to give 6-aminopenicillanic acid, was found to be widespread among micro-organisms. Partial purification of the enzyme, which was essentially exocellular, was obtained by precipitation with ammonium sulphate, or acetone, followed by dialysis. The pH optimum with phenoxymethylpenicillin as substrate was found to be approximately 9.0 with maximum enzyme stability at approximately pH 10.0. Over a relatively short period of reaction time the optimum temperature was approximately 50 °C. The K m value with phenoxymethylpenicillin was found to be 4.0 mg/ml. Using as substrate a concentration of 1 % phenoxymethylpenicillin, a conversion to 6-aminopenicillanic acid of 56 % of theoretical was obtained in the enzyme reaction mixture. Isolation of pure 6-aminopenicillanic acid from this reaction mixture was obtained in 50 % yield. 6-aminopenicillanic acid markedly inhibited the enzyme activity at a concentration of 4.0 mg/ml. Phenoxyacetic acid at this concentration was without effect. At higher concentrations, incubation of 6-aminopenicillanic acid and phenoxyacetic acid with the enzyme resulted in the synthesis of phenoxymethylpenicillin. The pH optimum for enzyme activity in the direction of synthesis was 5.0 to 5.5 compared with approximately 9.0 for hydrolysis.