. 2010 Jun 4;76(15):5067–5078. doi: 10.1128/AEM.00046-10

TABLE 1.

Comparison of maximum theoretical yields for the production of biofuels and biochemicals from fatty acids (palmitic acid) and lignocellulosic sugars (glucose)

Pathway stoichiometry for the synthesis of the specified product from glucose (C₆H₁₂O₆) or palmitic acid (C₁₆H₃₂O₂)^a	Maximum yield (wt basis/C basis)
Biofuels
Ethanol (C₂H₆O)
C₆H₁₂O₆ → 2C₂H₆O + 2CO₂	0.51/0.67
C₁₆H₃₂O₂ → 23/3C₂H₆O + 2/3CO₂	1.38/0.96
C₁₆H₃₂O₂ + 51/7H₂O → 53/7C₂H₆O + 6/7CO₂ + 8/7[H]; 8/7[H] + 2/7O₂ → 4/7H₂O	1.36/0.95
Butanol (C₄H₁₀O)
C₆H₁₂O₆ → C₄H₁₀O + 2CO₂ +H₂O	0.41/0.67
C₁₆H₃₂O₂ + 7/2H₂O → 53/14C₄H₁₀O + 6/7CO₂ + 8/7[H]; 8/7[H] + 2/7O₂ → 4/7H₂O	1.10/0.95
Biochemicals
Acetate (C₂H₄O₂)
C₆H₁₂O₆ + 2H₂O → 3C₂H₄O₂	1.00/1.00
C₁₆H₃₂O₂ + 7H₂O + 7CO₂ → 23/2C₂H₄O₂	2.70/1.44
Acetone (C₃H₆O)
C₆H₁₂O₆ → 3/2C₃H₆O + 3/2CO₂ + 3/2H₂O	0.48/0.75
C₁₆H₃₂O₂ + 5/4H₂O + 5/4CO₂ → 23/4C₃H₆O	1.30/1.08
Isopropanol (C₃H₈O)
C₆H₁₂O₆ → 4/3C₃H₈O + 2CO₂ + 2/3H₂O	0.44/0.67
C₁₆H₃₂O₂ + 40/9H₂O → 46/9C₃H₈O + 2/3CO₂	1.20/0.96
Succinate (C₄H₆O₄)
C₆H₁₂O₆ + 6/7CO₂ → 12/7C₄H₆O₄ + 6/7H₂O	1.12/1.14
C₁₆H₃₂O₂ + 152/17CO₂ + 86/17H₂O → 106/17C₄H₆O₄ + 80/17[H]; 80/17[H] + 20/17O₂ → 40/17H₂O	2.87/1.56
Propionate (C₃H₆O₂)
C₆H₁₂O₆ → 12/7C₃H₆O₂ + 6/7CO₂ + 6/7H₂O	0.70/0.86
C₁₆H₃₂O₂ + 262/83CO₂ + 370/83H₂O → 530/83C₃H₆O₂ + 216/83[H]; 216/83[H] + 54/83O₂ → 108/83H₂O	1.81/1.20

Stoichiometry is based on the pathways shown in Fig. 1 for the utilization of FAs and glucose, the synthesis of products, the TCA cycle, and oxidative phosphorylation. For the synthesis of biochemicals, CO₂ fixation via the Wood-Ljungdahl pathway (50) (2CO₂ + ATP + 8[H] → acetyl-CoA) or the carboxylation of phosphoenolpyruvate (54) (phosphoenolpyruvate + CO₂ → oxaloacetate + ATP) were also considered (not shown in Fig. 1). The stoichiometric coefficients were obtained by conducting elemental balances on carbon, hydrogen, and oxygen. An ATP balance was also included in the analysis for the reactions shown in italics. All other reactions represent ATP-generating pathways. Every acetyl-CoA oxidized through the TCA cycle generates three NADH, one reduced flavin adenine dinucleotide (FADH₂), and one ATP equivalent. Eleven ATPs can be generated from the oxidation of the NADH and FADH₂ produced in the TCA cycle (two and three ATPs per FADH₂ and NADH, respectively) via coupling between the electron transfer chain and oxidative phosphorylation.