Decreased O-2 supply during the fermentative production of gallidermin by Staphylococcus gallinarum decreased biomass formation by 65% compared to that obtained with optimal oxygen supply. However the antibiotic, gallidemin, increased by more than 50% at the same time. This effect was used in a process strategy, that allows biomass formation under oxygen saturation first and then switches to a prolonged production phase after a carefully directed shift to oxygen limitation.