Decreased production of para-hydroxypenicillin V in penicillin V fermentations.
Penicillin V (phenoxymethyl penicillin) is produced by industrial strains of Penicillium chrysogenum in the presence of phenoxyacetic acid (POAc), a side-chain precursor for the penicillin V molecule. The wild-type strain of P. chrysogenum produces an undesirable penicillin byproduct, para-hydroxypenicillin V (p-OH penicillin V), in addition to penicillin V, via para-hydroxylation of POAc and subsequent incorporation of the p-OH phenoxyacetic acid into the penicillin molecule. Most of the p-OH penicillin V is produced late in cycle when the POAc concentration in the medium is nearly depleted. The level of p-OH penicillin V produced by the control strain ranges up to 10-15% of the total penicillins produced. 3-Phenoxypropionic acid and p-bromophenylacetic acid partially inhibit the formation of p-OH penicillin V with a minimal effect on penicillin V productivity. Mutants deficient in their ability to hydroxylate POAc were found to produce lower levels of p-OH penicillin V. Multi-step mutation and screening, starting with the wild-type strain, have culminated in isolation of mutants which produce p-OH penicillin V as 1% of the total penicillins with no adverse effect on penicillin V productivity.