Literature-cited publications have focused on the development of fed-batch processes for SCO production using various feeding strategies. The application of fed-batch processes with feedback control has not been addressed extensively though. Zhang et al. (2011b) carried out fed-batch fermentations for SCO production in a 30-L bioreactor with Cryptococcus curvatus O3 using glucose as the sole carbon source and obtained a total dry weight, lipid content, and lipid productivity of 104.1 g/L, 82.7% (w/w), and 0.47 g/L/h, respectively. Intermittent feeding of a highly concentrated glucose solution was employed. Li et al. (2007) developed a fed-batch process with a nutrient-rich initial substrate and a sole carbon source intermittent feeding in a 15-L bioreactor. A final concentration of 106.5 g/L of total dry weight was achieved with 67.5% (w/w) SCO content and 0.54 g/L/h of SCO productivity.

Meesters et al. (1996) employed a two stage fed-batch fermentation process using glycerol as carbon source to produce high cell densities of 118 g/L with a lipid production rate of 0.59 g/L/h and a low cellular lipid content of 25% (w/w). A large inoculum was used in order to decrease the lag phase. Higher total dry weights (185 g/L and 153 g/L) with reasonably high lipid contents (40% and 54%, w/w) have been achieved in other studies employing fed-batch fermentations with the yeast strains Rhodotorula glutinis and Lipomyces starkeyi, respectively (Pan et al., 1986; Yamauchi et al., 1983). Pan et al. (1986) employed a fed-batch technique without feedback control where the feeding solution (containing 600 g/L glucose, 20 g/L yeast extract, and 9 g/L MgSO₄·7H₂O) was intermittently added. The relatively low-lipid content obtained could be attributed to the high concentration of nutrients added during feeding. The fed-batch process employed by Yamauchi et al. (1983) was based on ammonium ion limitation. Specifically, when the concentration of the ammonium ion in the cultivation medium was deficient after 48 h, a TDW of 153 g/L with a lipid content of 83 g/L was achieved.