Fatty acid composition of R. toruloides in fed-batch cultures. Cells were grown in defined medium with glucose (open symbols) or a mixture of glucose, xylose and arabinose (6:55:8, solid symbols) provided as carbon sources with (NH4)2SO4 as nitrogen source (pH 4, 30°C). The C/N during the batch phase for cultures which received no N in the feed (squares) was 40, whereas cultures with N in the feed (circles) received C/N 65 or 80 during both batch and feeding phases. Data for all cultures receiving N in the feed (C/N 65 or 80, constant or pulsed feed) have been combined and error bars represent ± SEM for 2–5 cultivations. Data for batch cultures (no feed, triangles) with glucose (70 g l−1, C/N 65) or glucose, xylose and arabinose (6:55:8, C/N 65) are also shown.