Saccharopolyspora erythraea was grown in an oil-based process medium at two different laboratory scales. The initial concentration of rapeseed oil in the medium was shown not to affect the growth, while addition of oil significantly increased erythromycin A production. Increasing the agitation speed at the 2 L scale increased the growth of the culture and the production of erythromycin A but had little effect on the level of oil remaining in the fermentation. Maximum oil utilization of 50% (w/w) was obtained in both 2 and 7 L cultures. Gas chromatography analysis of the process medium showed that there was no accumulation of fatty acids and glycerides during the fermentations. The specific oil utilization by the recombinant strain of S. erythraea was significantly lower compared to the wild-type strain grown at the same scale and initial oil concentration; the recombinant strain also produced lower concentrations of the novel polyketide, triketide lactone.