Metabolic Behavior and Chlortetracycline Production by Streptomyces aureofaciens in Liquid Culture.

Standard fermentations were performed as follows: A spore suspension was inoculated into 3 L of the following medium: sucrose, 3 per cent; corn steep liquor, 1 per cent; molasses, 0.1 per cent; NaCl, 0.05 per cent; and CaCO3, 0.4 per cent. The fermentations were carried out at 27 C in 5-L fermentors (Bartholomew, Karow and Sfat, 1950). After 36 hours, 100 ml of the culture fluid was transferred into three liters of the fermentation standard medium (U.S. Patent 1952): sucrose, 3 per cent; corn steep, 1 per cent; CaCO3, 1 per cent; (NH4)2 SO4, 0.2 per cent) and incubated in a 5-L fermentor at 27 C. Media were sterilized at 120 C for 60 minutes; the sucrose was separately sterilized. Aliquots were taken from the fermentors at suitable intervals of time and the following assays were performed: 1. Weight of mycelium: 5 or 10 ml were acidified with HCI in order to dissolve the calcium salts, then filtered; the washed mycelium was dried and weighed. 2. Protein nitrogen: 5 or 10 ml of the sample were made up to 10 per cent with trichloroacetic acid (TCA) and spun. After washing the sediment with 10 per cent TCA, nitrogen was determined according to the Kjeldahl method. 3. Nucleic acids: Pentose nucleic acid (RNA) and desoxypentose nucleic acid (DNA) contents were estimated, according to Ogur and Rosen (1950), in 1 or 2 ml of the sample. Histochemical researches, which will be published elsewhere, gave evidence that Ogur and Rosen's method for separation and extraction of nucleic acids may be used for Streptomyces (T. Scotti and P. Zoc.chi, personal communication). The nucleic acids were spectrophotometrically estimated. The interference of the chlortetracycline was totally eliminated by ethanol and 0.2 N perchloric acid washings before the nucleic acids extraction. In the first experiments,