The effect of cycling dissolved oxygen tension on the synthesis of the antibiotic difficidin by bacillus subtilis

Abstract

The antibiotic, difficidin, and its hydroxylated derivative, oxydifficidin, were synthesised by cultures of Bacillus subtilis grown on a complex medium in batch culture at dissolved oxygen tensions (DOT) of 15, 20 and 40% air saturation. During part of the growth phase the DOT was cycled about the control value and the effect on growth and antibiotic production observed. In fermentations with cycling at 15 and 20% DOT the growth yields were lower than for the fermentations done at constant DOT throughout. There appears to be a complex interaction between growth rate and difficidin production rate which led to a reduced specific production rate at 15% DOT as a result of cycling.