GLYCEROL EFFECT ON SPIRAMYCIN PRODUCTION AND VALINE CATABOLISM IN STREPTOMYCES-AMBOFACIENS

Spiramycin production by Streptomyces ambofaciens in a chemically defi ned medium, with valine as nitrogen source, was controlled by the natu re and the concentration of the carbon source. The production of this antibiotic was better in dextrins than in glycerol-containing medium. The negative effect of glycerol could be attributed in part to an exce ss of energy and a high specific growth rate. The intracellular ATP co ntent, at the start of spiramycin production, was twofold higher in gl ycerol than in dextrin-containing medium. Increasing the initial conce ntrations of glycerol led to an increase in the specific growth rate a nd a drop in spiramycin production. Comparison between glycerol and a protein synthesis inhibitor effects and the use of resting cell system s (RCS) proved that glycerol exerted both inhibitory and repressive ac tions on spiramycin production independently from the growth. At the e nzymatic level, glycerol interfered with valine catabolism by repressi ng partially valine dehydrogenase (VDH) and alpha-ketoisovalerate dehy drogenase (KIVDH), generator of spiramycin aglycone precursors.