A Comparison of Penicillin-producing Strains of Penicillium notatum-chrysogenum.

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 diluted 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 0.1 N H2S04 and frozen until sugar determinations and Kjeldahl nitrogen determinations could be made. The remainder of each ifitered sample was also frozen and saved for the ammonia determination. The pH values were determined on the original unifitered samples by means of a glass electrode. PeniciUin assay. The cylinder plate assay for penicillin (Abraham et al., 1941; Schmidt and Moyer, 1944) was used with modifications. Staphylococcus aureus 209-P was used as the test organism. Eight plates were set up for each two samples and the results averaged. The standard penicillin was checked against a Food and Drug Administration standard (penicillin G). Sugar determination. The lactose in diluted samples was hydrolyzed by heating to 120 C for 30 minutes in 0.75 N HCl. Sugar analysis was conducted by the method of Shaffer and Somogyi (1933). Reagent 50 with 5 grams of KI was used, and the samples were heated for 30 minutes in the boiling water bath. Glucose and lactose values were determined from appropriate calibration curves. Totl nitrogen. The total nitrogen of the filtrates was also determined on the diluted samples by the micro-Kjeldahl method described by Johnson (1941).