Growth curves and maximum production of lactate, acetate and ethanol by C. cellulolyticum strains. (A) Growth measured by optical density at 600 nm (OD600) in 5 g/l cellobiose. Wild-type (WT) and spo0A mutant reached a similar maximum growth, and spo0A mutant had a slightly lagged log phase. (B) Growth measured by total cellular protein in 10 g/l cellulose. WT and spo0A mutant reached a similar maximum growth, and spo0A mutant had a more obvious lagged log phase. (C and D) Final metabolic product concentrations measured for WT and spo0A mutant in 5 g/l cellobiose and 10 g/l cellulose, respectively. In both of the carbon sources, the WT and spo0A mutant produced similar amounts of lactate, acetate and ethanol. The error bars represent standard deviations of measurements from three replicate cultures.