Fig. 3

Effects of changes in lipid content on cellular metabolism. To test the impact of increasing lipid synthesis rates, calculations with increasing lipid content in the biomass were performed, ranging from 0.4 to 60 %. a: The glucose uptake rate was constrained to 4 mmol g⁻¹ h⁻¹. Under these conditions, the model predicted a reduced growth rate and an increase of the respiratory quotient (CO₂/O₂), mainly due to a drop of the oxygen uptake rate. Besides, the expected increase in demand for NADPH and acetyl-CoA was observed. b: If the growth rate was constrained, the glucose uptake rate increased with lipid content. The oxygen uptake rate decreased, despite increasing glucose uptake and constant growth rate, suggesting that higher lipid synthesis rates result in reduced demand for oxygen. c: Robustness analysis showed that the growth rate of Y. lipolytica is negatively affected by decreasing oxygen uptake rates before lipid synthesis, suggesting that a fermentation with reduced aeration will result in arrest of growth but not lipid synthesis