Evaluation of Precursors for Penicillin G

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Abstract
Marked increases in total penicillin yield and proportion of penicillin G were obtained in submerged cultures of Penicillium chrysogenum Q176 in a synthetic medium by the addition of beta-phenylethylamine and phenylacetic acid. No penicillin G was detected when no precursor was added. Max. precursor efficiency was obtained when the precursor was added in many equal portions at intervals. The opt. concn. of phenylacetic acid to be added at 12-hr, intervals was 0.10 to 0.15% and penicillin yields (practically pure G) averaged 685 U. per ml. on synthetic medium and 892 U. per ml. on corn steep liquor medium. From 71% to 94% of the added phenylacetic acid was metabolized in ways other than the production of penicillin G. The opt. pH range during the fermentation was 7.6 - 7.9. The percentage of penicillin G was low at an acid pH. Attempts to replace effectively phenylacetic acid with some of its derivatives have been unsuccessful. The percentage of penicillin G remained practically constant during the course of fermentation with phenylacetic acid or phenylacetamide as precursors. It increased during the fermentation with phenylacetylglycine and phenyl-acetyl-DL-alanine but decreased with beta-phenylethylamine, DL-phenylalanine, and octadecanol phenylacetate.