TABLE 1.

Thermodynamics of biochemical reactions involved in conversion of xylose to butyrate, hexanoate, and octanoate^a

Equation no.	Equation	Associated MAG(s)	ΔG per mol substrateb (kJ mol−1)			YATP (mol ATP mol−1 substrate)b ,c	ΔG0' available per ATP produced (kJ mol−1 ATP)	Terminal enzyme
			PH2 = 10–6 atm	PH2 = 1 atm	PH2 = 6.8 atm
Xylose simple fermentation
1	3 C5H10O5 → 5 C3H5O3- + 5 H+	LAC1, LAC2, LAC4, LAC5	−174	−174	−174	1.67	−104 to −104
2	3 C5H10O5 → 3 C3H5O3- + 3 C2H3O2- + 6 H+	LAC1, LAC2, LAC4, LAC5	−214	−214	−214	2.00	−107 to −107
Xylose elongation
3	3 C5H10O5 → 3 C4H7O2- + 3 CO2 + 3 H2O + 3 H+	LCO1	−264	−264	−264	3.00	−88 to −88	CoAT
4	3 C5H10O5 → 1 C6H11O2- +3 C2H3O2- + 3 CO2 + 4 H+ + 2 H2	LCO1	−272	−248	−245	2.83	−87 to −96	CoAT
5	3 C5H10O5 → 1 C8H15O2- + 2 C2H3O2- + 3 CO2 + 3 H2O + 3 H+	LCO1	−265	−265	−265	3.00	−88 to −88	CoAT
6	2 C5H10O5 → 1 C4H7O2- + 2 C2H3O2- + 2 CO2 + 3 H++ 2 H2	LCO1	−276	−240	−235	2.25	−105 to −123	TE
7	3 C5H10O5 → 1 C6H11O2- + 3 C2H3O2- + 3 CO2 + 1 H2O + 4 H+ + 2 H2	LCO1	−272	−248	−245	2.50	−98 to −109	TE
8	4 C5H10O5 → 1 C8H15O2- + 4 C2H3O2- + 4 CO2 + 2 H2O + 5 H++ 2 H2	LCO1	−270	−253	−250	2.63	−95 to −103	TE
Xylose and C2/C4/C6d elongation
9	1 C5H10O5 + 2 C2H3O2- + 2 H2 → 2 C4H5O2- + 1 CO2 + 3 H2O	LCO1	−240	−311	−320	3.50	−69 to −92	CoAT
10	1 C5H10O5 + 1 C2H3O2- + 2 H2 → 1 C6H11O2- + 1 CO2 + 3 H2O	LCO1	−240	−311	−320	3.50	−69 to −92	CoAT
11	1 C5H10O5 + 1 C4H7O2- + 2 H2 → 1 C8H15O2- + 1 CO2 + 3 H2O	LCO1	−264	−264	−264	3.50	−75 to −75	CoAT
12	1 C5H10O5 + 1 C4H7O2- → 1 C6H11O2- + 1 C2H3O2- + 1 CO2 + 1 H2O + 1 H+	LCO1	−243	−314	−324	3.00	−81 to −108	CoAT
13	1 C5H10O5 + 1 C6H11O2- → 1 C8H15O2- + 1 C2H3O2- + 1 CO2 + 1 H2O + 1 H+	LCO1	−267	−267	−267	3.00	−89 to −89	CoAT
14	1 C5H10O5 + 2 C2H3O2- + 2 H2 → 2 C4H5O2- + 1 CO2 + 3 H2O	LCO1	−240	−311	−320	1.50	−160 to −214	TE
15	1 C5H10O5 + 1 C2H3O2- + 2 H2 → 1 C6H11O2- + 1 CO2 + 3 H2O	LCO1	−240	−311	−320	2.50	−96 to −128	TE
16	1 C5H10O5 + 1 C4H7O2- + 2 H2 → 1 C8H15O2- + 1 CO2 + 3 H2O	LCO1	−264	−264	−264	2.50	−105 to −105	TE
17	1 C5H10O5 + 1 C4H7O2- → 1 C6H11O2- + 1 C2H3O2- + 1 CO2 + 1 H2O + 1 H+	LCO1	−243	−314	−324	2.00	−122 to −162	TE
18	1 C5H10O5 + 1 C6H11O2- → 1 C8H15O2- + 1 C2H3O2- + 1 CO2 + 1 H2O + 1 H+	LCO1	−267	−267	−267	2.00	−133 to −133	TE

^aFree energies of formation for all chemical compounds were obtained from Kbase (www.kbase.us). The ATP yield (Y_ATP) was determined on the basis of biochemical models presented in Data Set S7 and is indicated as moles of ATP produced per mole of xylose consumed. The terminal enzyme of reverse β-oxidation, i.e., either a CoA transferase (CoAT) or thioesterase (TE), is also indicated.

^bΔG values and expected ATP yields are normalized to moles of xylose, moles of lactate, or moles of glycerol.

^cThe pathway reconstructions shown in Data Set S7 were used to determine the expected ATP yields.

^dThese scenarios considered coutilization of xylose and acetate (C2), butyrate (C4), or hexanoate (C6).