There have been many studies showing that redox control has
shifted the metabolism from reductive to oxidative and vice versa.
It was shown that artificial electron carriers such as methyl viologen
and neutral red caused significant carbon flow shift from acids
to alcohols production in C. acetobutylicum accompanied by
decreased hydrogen evolution (Girbal, 1995). Microaerobic conditions
were found to shift the metabolism from reductive to oxidative
and reduce PDO production substantially in C. butyricum
(Pachapur et al., 2015). Similarly, it was found in this study, the
PDO production was reduced at low pH values, which in turn
resulted in slightly higher redox potential (Fig. 2B). It can be postulated
that the redox potential was controlled through low pH (this
study) and microaeration (Pachapur et al., 2015), in both cases
effecting the product distribution.