Uptake of phenoxyacetic acid by Penicillium chrysogenum

The uptake of phenoxyacetic acid by two different strains of Penicillium chrysogenum was studied. Phenoxyacetic acid (POA) was taken up by P. chrysogenum in a defined medium. Plots of initial velocity of POA uptake versus external substrate concentration, in the range 2-5000 microM, gave linear plots. Uptake of POA by induced and uninduced cells was identical. The initial velocity of POA uptake decreased as the pH of the suspension was increased from 5.4 to 7.2; the decrease closely paralleled the decline in the non-ionic form of the acid over this pH range. The initial velocity of POA uptake was not affected by the presence of phenylacetic acid. POA uptake proceeded until the cellular concentration was equal to the external concentration. It is concluded that POA is passively transported into P. chrysogenum by unmediated diffusion.

Utilization of side-chain precursors for penicillin biosynthesis in a high-producing strain of Penicillium chrysogenum

Utilization of the side-chain precursors phenoxyacetic acid (POA) and phenylacetic acid (PA) for penicillin biosynthesis by Penicillium chrysogenum was studied in shake flasks. Precursor uptake and penicillin production were followed by HPLC analysis of precursors and products in the medium and in the cells. P. chrysogenum used both POA and PA as precursors, producing phenoxymethylpenicillin (penicillin V) and benzylpenicillin (penicillin G), respectively. If both precursors were present simultaneously, the formation of penicillin V was blocked and only penicillin G was produced. When PA was added at different times to cells that were induced initially for POA utilization and were producing penicillin V, the POA utilization and penicillin V formation were blocked, whereas the cells started utilizing PA and produced penicillin G. The blocking of the POA turnover lasted for as long as PA was present in the medium. If POA was added to cultures induced initially for PA utilization and producing penicillin G, this continued irrespective of the presence of POA. Utilization of POA increased concomitant with depletion of PA from the medium. Analysis of cellular pools from a growing cell system with POA as precursor to which PA was added after 48 h showed that the cellular concentration of POA was kept high without production of penicillin V and at a concentration comparable to the concentration in the medium. The cellular concentration of POA was higher than the concentration of PA that was utilized for penicillin G production.