Table 1.

Calculated maximum TYs of selected FFAs on renewable carbon sources^a,^b

	TY (g FFA per g carbon source)
FFA	Glycerol	D-Glucose	D-Xylose	L-Arabinose
Lauric (12:0)	0.39	0.35	0.29	0.29
Myristic (14:0)	0.38	0.34	0.29	0.28
Palmitic (16:0)	0.37	0.34	0.28	0.28
Lauroleic (12:1Δ5)	0.40	0.37	0.31	0.30
Myristoleic (14:1Δ7)	0.39	0.35	0.30	0.29
Palmitoleic (16:1Δ9)	0.38	0.35	0.29	0.28

^aValues were calculated by constraint-based modeling using the iAF1260 metabolic network reconstruction of E. coli with reactions added to enable extracellular transport of all listed FFA species and hydrolysis of acyl-ACP species. Maximization of extracellular FFA flux was performed, with reactions catalyzed by PlsB constrained to zero flux to force FFA formation by hydrolysis of acyl-ACPs.

^bIt should be noted that the theoretical mass yields presented here do not reflect the yield of chemical energy, which is significantly higher. For example, theoretical conversion of 2.83 mol of glucose to 1 mol of lauric acid, 5 mol of CO₂, and 5 mol of H₂O has an enthalpy of reaction of –558 kcal/mol based on standard heats of formation. This represents retention of 84% of the enthalpy in the glucose. This compares favorably with the case of ethanol production in which 94% of the enthalpy is retained.