Increased levels of ATP and NADH are associated with increased solvent production in continuous cultures of Clostridium acetobutylicum

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Levels of intracellular NAD, NADH, ADP, and ATP were measured in batch and continuous cultures of Clostridium acetobutylicum. ATP levels during glucose-sufficient (non-glucose limited), solvent-producing steady states were five to eight times as high as in glucose-limited (acidogenic) steady state cultures (4.8 μmole/g versus 0.9 μmole/g). NADH was also higher in glucose-sufficient cultures, although the increase was not as pronounced as with ATP. When glucose-limited cultures were sparged with CO, the resulting shift to solvent production was accompanied by three- or four-fold increases in NADH and ATP levels. In batch cultures, NADH and ATP levels were relatively high at all times compared to levels in continuous cultures. Although the levels of these nucleotides showed systematic trends during normal batch fermentations, there was no significant change with the onset of solvent production.