Effect of butyrate supplementation on butanol production and metabolic behavior in Clostridium acetobutylicum ATCC 824 (pCD07239)

In this study, we investigated the effects of initial butyrate supplementation on the metabolic behavior and butanol production of the non-traditional butanol-producing strain Clostridium acetobutylicum ATCC 824 (pCD07239). Batch fermentations were conducted under three conditions: without initial butyrate, with 2 and 5 g/L initial butyrate. The strain consistently initiated butanol production as early as 3 h into the process during the early log phase under all conditions. The addition of 2 g/L butyrate slightly enhanced butanol production to 14.2 g/L, while 5 g/L butyrate resulted in a slightly lower butanol titer of 12.7 g/L, suggesting an inhibitory effect at higher concentrations. In comparison, the butanol titer without initial butyrate feeding was 13.6 g/L. Butyrate production patterns varied: in the control, it was negligible during the log phase and increased to 4.7 g/L during the stationary phase. With 2 g/L butyrate, the concentration remained constant during the log phase and increased to 5.7 g/L during the stationary phase. With 5 g/L butyrate, the concentration decreased to 1.8 g/L during the log phase, indicating reassimilation, and increased to 3.8 g/L during the stationary phase. Acetate production was suppressed to around 3 g/L with both 2 and 5 g/ L butyrate supplementation. These results indicate that butyrate supplementation can enhance butanol production, but higher concentrations may inhibit the process in the strain ATCC 824 (pCD07239). Further research is needed to understand the genetic and metabolic mechanisms and to optimize fermentation conditions for industrial applications.