THE EFFECT OF CYCLING DISSOLVED-OXYGEN TENSION ON THE SYNTHESIS OF THE ANTIBIOTIC DIFFICIDIN BY BACILLUS-SUBTILIS

The antibiotic, difficidin, and its hydroxylated derivative, oxydiffic idin, were synthesised by cultures of Bacillus subtilis grown on a com plex medium in batch culture at dissolved oxygen tensions (DOT) of 15, 20 and 40% air saturation. During part of the growth phase the DOT wa s cycled about the control value and the effect on growth and antibiot ic production observed. In fermentations with cycling at 15 and 20% DO T the growth yields were lower than for the fermentations done at cons tant DOT throughout. There appears to be a complex interaction between growth rate and difficidin production rate which led to a reduced spe cific production rate at 15% DOT as a result of cycling.