Fig. 2

Ethanol titer in the presence of different concentrations of added ethanol. Four engineered strains of C. thermocellum (LL1210, LL1570, LL1592, and LL1679) were compared to an uninoculated control (Evap. ctrl.), and an ethanol-tolerant strain of Thermoanaerobacterium saccharolyticum (M1442). The data for strain LL1210 are from [2] and is included for purposes of comparison. Cells were grown in MTC defined medium with 50 g/L cellobiose in sealed glass bottles. WT C. thermocellum was not included since it is not able to consume 50 g/L cellobiose in the absence of pH control. Total ethanol titer is shown, representing the sum of initially present and produced ethanol. Strain genotypes are described in more detail in Fig. 1 and Table 2