Figure 3: Fermentation profiles of pex10 mfe1 leucine⁺ uracil⁺ DGA1 and POlf leucine⁺ uracil⁺.

Time courses of the 1.5 l scale batch fermentation of the pex10 mfe1 leucine⁺ uracil⁺ DGA1 (a,b) and POlf leucine⁺ uracil⁺(c,d) strains in 80 g l⁻¹ glucose, 6.7 g l⁻¹ YNB (no amino acids, 1.365 g l⁻¹ ammonium) are shown, including production of biomass, lipids and citric acid (left axis a,c), consumption of glucose (right axis a,c), and ammonium level (b,d). (a) During the pex10 mfe1 leucine⁺ uracil⁺ DGA1 fermentation, negligible citric acid was produced and lipid product accumulated during and after biomass production phases. This fermentation was run three times in identical conditions, reaching final yields of 15.25 g l⁻¹ lipids and 20.3 g l⁻¹ biomass (75% lipid content), 14.96 g l⁻¹ lipids and 20.6 g l⁻¹ biomass (73% lipid content), and 16.9 g l⁻¹ lipids and 19.21 g l⁻¹ biomass (88% lipid content). Most time points show average values from the former two fermentations (75 and 73% final lipid content), while end-points represent averages from all three final values. Error bars represent s.d. of these technical replicates. Glucose and ammonium substrate were fully consumed after 72 h, but surprisingly, (b) ammonium level was replenished to a steady state level of ~0.5 g l⁻¹, ~40% of the original starting level. (c) During the POlf leucine⁺ uracil⁺ fermentation, citric acid accumulated to more than 14 g l⁻¹ after 72 h before quickly reducing to 4 g l⁻¹. Lipid production did not trend with biomass production, reaching a final yield of only 3 g l⁻¹ lipids, compared with 30 g l⁻¹ biomass and glucose was again consumed within 72 h. (d) Ammonium was fully consumed after 72 h with no replenishment as observed in the mutant strain.