A comparison of penicillin-producing strains of Penicillium notatum-chrysogenum

Most of the work reported in this paper was done under a government-spon-sored co-operative research program. One of the problems at this laboratory involved a comparison of the various strains of the Penicillium notatum-chry-ogenum group which have been isolated or developed in oo-operating laboratories. EXPERIMENTAL METHODS Sampling and storage. The fermentations were conducted in the 100-gallon tanks described by Stefaniak et al. (1946). Samples were removed periodically into 500-ml flasks and ifitered. A 0.5-ml filtered sample was immediately di-luted for penicillin assay by addition to previously chilled phosphate buffer in volumetric flasks (4.0 g KH2P04 and 1.0 g K2HPO4 per 500 ml solution in distilled water; pH 5.9 to 6.0). These flasks were stored at 10 C until they were assayed for penicillin (usually no longer than 16 hours). Samples kept 2 days showed no change in potency greater than the variations to be expected in the assay, ca. 5 to 10 per cent. A 1.0-ml filtered sample was diluted to 10.0 ml with 0.