Fig. 3

Specific BV:PFOR activity (a) and fermentation products (b) for 13 strains of C. thermocellum. The plus sign indicates the presence of a genetic modification in a strain. For enzyme activity, 1 unit (U) is equivalent to the formation of 1 µmol of product per minute. For the fermentations, cultures were grown in sealed serum bottles with 20 mL of MTC-5 medium with 145 ± 2 mM initial cellobiose (~ 50 g/L) for 168 h at 55 °C, with 180 rpm shaking. Values over the ethanol (red) columns represent the metabolic yield of ethanol as a percentage of theoretical maximum (assumes that a maximum of 2 moles of ethanol can be produced from 1 mole of glucose or glucose equivalent). Error bars represent one standard deviation (n ≥ 2 for enzyme specific activity, n ≥ 3 for fermentation products). Raw data and growth rates are presented in Additional file 1: Table S3; individual quantification of extracellular amino acid production is shown in Additional file 1: Table S4