Table S1.

Carbon input and output in C. thermocellum fermentation (non–pH-controlled, buffered with 50 mM MOPS) with and without bicarbonate supplementation

Substrate		Consumption, mM	Production, mM							Apparent carbon efficiency,† %
Cellobiose, 14.6 mM	Bicarbonate, 20 mM	Cellobiose	Lactate	Formate	Acetate	Ethanol	Final OD600	Cbiomass*	H2
Positive	Negative	11.8 ± 0.2	5.9 ± 0.2	4.9 ± 0.8	8.6 ± 0.7	14.7 ± 0.6	0.9 ± 0.0	41.6 ± 0.5	12.4	78.4
Positive	Positive	14.5 ± 0.0	10.3 ± 1.6	7.8 ± 0.3	11.2 ± 0.1	20.6 ± 0.2	1.0 ± 0.0	45.6 ± 0.6	13.3	84.8
ΔCcellobiose,‡ mM		32.7
ΔCproduct,§ mM		36.9

Values are reported as average ± SD (n = 3).

^*Carbon molarity in cell biomass (C_biomass) is calculated based on the C. thermocellum formula C₅H₈O₂N and measured OD₆₀₀ value, which is equal to 1.04 g/L OD₆₀₀ cell dry weight, approximately.

^†Apparent carbon efficiency is defined in this case as the ratio of produced organic carbons to consumed organic carbons following the calculation: (C_lactate + C_formate + C_acetate + C_ethanol + C_biomass)/C_cellobiose.

^‡ΔC_cellobiose refers to the amount of carbons in cellobiose that were consumed more in the bicarbonate-fed culture than in the culture fed with only cellobiose.

^§ΔC_product refers to the total amounts of carbon in lactate, formate, acetate, ethanol, and biomass that were produced more in the bicarbonate-fed culture than in the culture fed with only cellobiose.