Saccharopolyspora erythraea growth is inhibited when grown at a low constant dissolved oxygen tension (DOT) of 10% air saturation. However, the specific erythromycin production is virtually identical to that of a culture where the DOT did not fall below 65%. In addition, at constant DOT (10%) a stirrer speed of 750 rpm in a 7 litre causes mechanical damage to the mycelia in comparison with result at 500 rpm.