Abstract
Substrate variability in multi-feedstock biorefineries has implications for the stability of downstream bioprocesses. Here, we studied potential effects of fluctuating feed rates and pH on substrate uptake and butanol production by Clostridium saccharoperbutylacetonicum during continuous co-feeding with butyric and acetic acid. Monitoring the fermentation extensively and at high frequency, enabled us to perform irregular fraction experimental designs. The total acid feed rate and the ratio of butyric acid to acetic acid in the feed were found to be significant factors in their uptake by the culture. Furthermore, to maximize the specific butanol production rate, glucose may not be limited and butyric acid should be supplied at a rate of 7.5 mmol L−1 h−1. Surprisingly, pH played a role only indirectly, in its effect on process stability. Obtained results facilitate the control of feed rates based on physiological descriptors, which will be a critical factor in the establishment of multi-feedstock biorefineries.
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