Comparison of mutant and parent strains of Clostridium acetobutylicum: butyrate uptake at different temperatures

A high butanol producing mutant strain of Clostridium acetobutylicum ATCC 4259 was obtained by chemical mutagenesis. Both mutant and parent strains were evaluated for butyrate uptake using the culture effluents of solventogenic fermentor-2 of the two-fermentor continuous system. Batch incubation of fermentor-2 culture effluents at 37 °C indicated lower butyrate uptake rates for mutant and parent strain, at 0.05 and 0.03 g l−1 h−1, respectively. Increased butyrate uptake rates of 0.33 and 0.26 g l−1 h−1 for mutant and parent strain, respectively, were observed when effluents were batch incubated at lower temperature of 30 °C. Butyrate conversion efficiency, at 5 ± 0.1 g l−1 of externally added butyrate, were 98.8% and 96.9% for mutant and parent strain, respectively. Butyrate up to the externally added concentration of 11.4 g l−1 did not inhibit butyrate uptake. The maximum butyrate consumption at a slightly reduced uptake rate was seen at 10.2 g l−1 butyrate concentration at 27 °C. Based on the results under different temperatures, the electron flow pattern has been computed and the mechanism for butyrate uptake has been hypothesized.