The effect of low oxygen uptake rate on the fatty acid profile of the oleaginous yeast Apiotrichum curvatum

Summary The effect of limiting the available oxygen on the fatty acid profile of Apiotrichum curvatum ATCC 20509 during growth on sulphuric acid casein whey was studied. At oxygen uptake rates (OUR) lower than 7 mmol O₂/l per hour, applied during the oil accumulating phase of the fermentation, a decrease in total unsaturated fatty acids was observed. It was possible to decrease the unsaturated fatty acids (oleate from 55% to 41% and linoleate from 9% to 3%) by limiting the OUR of the culture to <3 mmol O₂/l per hour. However at this low OUR, a lower oil coefficient (a measure of the efficiency of lactose substrate conversion to oil) was recorded. Furthermore the fermentation time was increased. An OUR of 5 mmol O₂/l per hour appeared to be the limit below which adverse effects on oil yields and increased fermentation times occurred. At this OUR, the accumulated oil contained 45% oleate and 5% linoleate. These effects were demonstrated in a 20-l air-lift fermentor and confirmed in a scaled down 500-l industrial type bubble column fermentor. Offprint requests to: R. J. Davies