Excellent incorporations of both D-[l-14C]-and L-[ U-14C]-valine into penicillin G by a high producing strain of Pencillium chrysogenum is reported ; the label from ~-[a-~H]-valine is not incorporated.

No abstract

IN TRO D U C T I 0 NClutterbuck et al. (1934) reported that the metabolic products of the mould Penicillium charlesii G. Smith grown on glucose as the carbon and energy source were two polysaccharides and six organic acids -carolic, carlosic, carlinic, carolinic, verticillic and ramigenic acids. Subsequent work showed that verticillic acid and ramigenic acid were artefacts arising from the reaction between a further acid product, y-methyltetronic acid, and the tetronic acids were detected. The time of initiation suggested that these occurred as secondary metabolic products. Itaconic acid was also detected in the culture medium but was only formed during the primary growth phase. METHODSOrganism and growth conditions. Isolates of Penicillium charlesii G. Smith IM140232 were obtained from the Commonwealth Mycological Institute, Kew. Stock cultures from single spore subcultures were maintained on slopes of 4 % (w/v) Oxoid potato dextrose agar in screw-capped bottles (15 ml). Cultures were grown at 25 "C until the surface was covered with conidia (3 to 4 weeks) and then used as a source of fungal spores. The medium used for the growth experiments was that described by Clutterbuck et al. (1935). Erlenmeyer flasks (100 ml) containing medium (20 ml) adjusted to pH 4.5 were inoculated with a suspension of conidia in sterile distilled water containing the neutral detergent Teepol L (0.01 % (w/v); BDH), to give a final concentration of 7.5 x 105 conidia ml-l. The cultures were incubated at 24+ I "C on a rotary shaker operating at 150 rev. mi+.Sampling methods. Sample flasks were taken at intervals throughout the culture period. The mycelium was harvested by filtration and the medium removed for analysis. After washing, the mycelium was dried to a constant weight at 110 "C.Analytical methods.