Figure 2

Genome-scale FBA models for predicting microbial biofuel yields from glucose. a. E. coli strains produce ethanol (growth rate = 0.05 h⁻¹). b. E. coli strains produce isobutanol (growth rate = 0.05 h⁻¹). c. E. coli strains produce fatty acid (growth rate = 0.05 h⁻¹). d. E. coli strains produce fatty acid (growth rate = 0.20 h⁻¹). We use an E. coli FBA model (iJO1366) to predict production of different biofuels from glucose. Alcohol production is simulated under the microaerobic condition (O₂ influx ≤ 1.85 mmol/(gDW∙hr)), while fatty acid is under aerobic condition (O₂ influx ≤ 12 mmol/ (gDW∙hr)). The medium conditions and glucose uptake rate (8 mmol/ (gDW∙hr)) are same for all FBAs. Extra metabolic burden is simulated by the costs of both protein overexpression and maintenance energy increase (e.g., 10% extra metabolic burden is equivalent to 10% overexpression of total biomass protein plus proportional increase of non-growth associated ATP loss). For each case, the objective function is set as to maximize the biofuel production. Abbreviations: DW (Dry Weight); FA (Fatty acid); Glc (Glucose); IB (Isobutanol).