Organic acid excretion by Streptomyces lividans TK24 during growth on defined carbon and nitrogen sources

1 The Advanced Centre for Biochemical Engineering, Department of Chemical and Biochemical Engineering, University College London, Torrington Place, London WC1E 7JE, UK 2 Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK ABSTRACT Cultures of Streptomyces lividans TK24 grown in defined media containing certain rapidly used carbon and nitrogen sources excreted high levels of organic acids. These were identified by HPLC and enzymic assays as pyruvic acid and 2-oxoglutaric acid. Acidification occurred only with glucose as the principal carbon source, and depended on the nitrogen source used. With nitrate as the sole nitrogen source, high levels of pyruvate and small amounts of 2-oxoglutarate were produced. Carbon from D-[U- 14 C]glucose was converted into both organic acids. Combining glucose with a selection of amino acids as primary nitrogen/secondary carbon sources yielded less pyruvate and more 2-oxoglutarate. Carbon from both 14 C-labelled glucose and amino acids was metabolized to both organic acids. Adding nitrate to this combination caused a reversion of the acid production pattern to that of the glucose-nitrate combination, as if the amino acids were absent. Addition of ammonium salts to any combination of carbon and nitrogen sources completely prevented organic acid formation. 3 Author for correspondence: John M. Ward. Tel: +44 171 387 7050 ext. 2242. Fax: +44 171 380 7193. e-mail: ward@bsm.bioc.ucl.ac.uk Keywords: Streptomyces lividans TK24, metabolism, pyruvic acid, 2-oxoglutaric acid, HPLC