Table 3.

Effect of CO partial pressure on glucose conversion and carbon recovery (%) by strain PCO, Thermoanaerobacter thermohydrosulfuricus (DSM 527^T), T. brockii subsp. finnii (DSM 3389^T), T. pseudethanolicus (DSM 2355^T), and T. wiegelii (DSM 10319^T).

Strains	CO (%)	Glucose consumed (mM)	Product yielda				CO2 producedb(mmol L−1medium)	Carbon recoveryc(%)
			mol H2/mol glucose	mol acetate/mol glucose	mol lactate/mol glucose	mol ethanol/mol glucose
Strain PCO	0	17.9 ± 1.80	0.22 ± 0.04	0.29 ± 0.04	0.92 ± 0.11	0.39 ± 0.07	12.2 ± 1.2	88.1 ± 9.4
	25	18.0 ± 0.80	0.08 ± 0.01	0.33 ± 0.03	0.93 ± 0.05	0.43 ± 0.02	13.7 ± 0.5	91.2 ± 4.4
	50	18.3 ± 1.24	0.05 ± 0.01	0.35 ± 0.06	0.85 ± 0.14	0.33 ± 0.04	12.3 ± 1.1	82.2 ± 8.8
	75	17.7 ± 1.54	0.06 ± 0.01	0.34 ± 0.06	0.93 ± 0.12	0.36 ± 0.07	12.3 ± 1.4	87.8 ± 9.3
	100	18.1 ± 0.22	<0.02	0.46 ± 0.03	0.78 ± 0.05	0.21 ± 0.02	12.2 ± 0.7	77.1 ± 2.9
T. thermohydrosulfuricus	0	17.8 ± 1.00	0.61 ± 0.06	0.38 ± 0.06	0.64 ± 0.09	0.86 ± 0.14	22.2 ± 2.6	102.3 ± 9.0
	50	15.7 ± 0.90	0.40 ± 0.08	0.28 ± 0.04	0.94 ± 0.14	0.58 ± 0.08	13.5 ± 1.3	100.9 ± 9.4
	100	15.2 ± 0.30	0.18 ± 0.01	0.20 ± 0.01	1.21 ± 0.05	0.37 ± 0.06	8.7 ± 1.0	100.0 ± 3.8
T. brockii subsp. finnii	0	14.2 ± 1.80	0.37 ± 0.05	0.48 ± 0.07	0.85 ± 0.11	0.66 ± 0.19	16.1 ± 2.6	113.7 ± 15.9
	50	14.9 ± 0.90	0.02 ± 0.002	0.32 ± 0.04	0.89 ± 0.06	0.70 ± 0.13	15.3 ± 1.9	112.4 ± 8.2
	100	15.7 ± 0.40	<0.02	0.30 ± 0.05	0.84 ± 0.04	0.66 ± 0.18	15.1 ± 2.9	105.6 ± 7.7
T. pseudethanolicus	0	16.6 ± 0.50	0.22 ± 0.02	0.40 ± 0.02	0.72 ± 0.03	0.63 ± 0.22	17.0 ± 3.6	100.7 ± 8.7
	50	17.1 ± 0.60	<0.02	0.26 ± 0.07	0.70 ± 0.06	0.68 ± 0.10	16.1 ± 2.0	91.4 ± 6.1
	100	16.0 ± 1.60	<0.02	0.29 ± 0.04	0.85 ± 009	0.61 ± 0.12	14.6 ± 1.6	97.5 ± 10.7
T. wiegelii	0	17.7 ± 1.80	0.90 ± 0.17	0.39 ± 0.108	0.22 ± 0.04	1.45 ± 0.22	32.6 ± 3.2	124.9 ± 14.3
	50	18.5 ± 1.20	0.71 ± 0.12	0.32 ± 0.03	0.26 ± 0.02	1.43 ± 0.13	32.3 ± 1.9	112.8 ± 8.0
	100	17.1 ± 1.70	0.05 ± 0.02	0.25 ± 0.08	0.91 ± 0.21	0.66 ± 0.26	15.5 ± 4.5	99.0 ± 16.7

^aProduct yield = (C_{P, tf} − C_{P, t0})/(C_{S, t0} − C_{S, tf}); where, C_P is product concentration and C_S is glucose concentration measure at time zero (t₀) and at the end of the assay (t_f). Note: final product concentration was calculated as an average of the plateau of production curves.

^bEstimated CO₂ production considering that 1 mol of CO₂ is produced for each mol of ethanol or acetate formed [a maximum deviation of 20% was obtained when estimating total CO₂ concentrations from measured CO₂ concentration in the headspace summed with the correspondent calculated dissolved CO₂ (using the Henry law)].

^cCarbon recovery (CR) = Σ (n_{P, tf} − n_{P, t0})/(n_{S, tf} − n_{S, t0}) + n_biomass; where n is the number of carbon moles in products (P − acetate, lactate, ethanol, and CO₂) and in glucose (S) and n_biomass is the estimated mol of carbon used for biomass growth.

For the calculation of n_biomass, cell density was analyzed photometrically by optical density at 600 nm (OD) and converted to cell dry weight per liter using experimentally determined conversion factors (OD/(g_dry−weight/L)) for each of the tested strains: 0.78 (strain PCO), 0.89 (T. thermohydrosulfuricus), 1.36 (T. brockii subsp. finnii), 1.04 (T. pseudethanolicus), and 0.86 (T. wiegelii).