TY - JOUR
T1 - Effect of pH in syngas conversion to C4 & C6 acids in mixed-culture trickle bed reactors
AU - Quintela, Cesar
AU - Grimalt-Alemany, Antonio
AU - Modin, Oskar
AU - Nygård, Yvonne
AU - Olsson, Lisbeth
AU - Skiadas, Ioannis V.
AU - Gavala, Hariklia N.
N1 - Publisher Copyright:
© 2024 The Authors
PY - 2024
Y1 - 2024
N2 - Syngas fermentation allows for the conversion of wastes into useful commodity chemicals. To target higher value products, the conditions can be tuned to be favourable for both acetogenic and reverse beta-oxidation pathways and produce, in one stage, butyric and caproic acid. Studies in CSTR have shown the crucial role of pH, which must be low enough to allow for ethanol generation in the acetogenic step while avoiding the inhibition of reverse β-oxidation in acidic conditions. However, no studies have investigated the effect of pH in reactor configurations suitable for syngas fermentation (i.e., allowing for cell retention and exhibiting high mass transfer rates at low operating costs), such as Trickle Bed Reactors, TBR. In this study, two TBR were used to study the pH effect on the fermentation of syngas to produce C4 and C6 acids, using undefined mixed cultures. Five pH values were tested in the range 4.5–7.5, and pH 6 was found to be the most favourable for simultaneous production of C4 & C6 acids from syngas, which agrees with what was found in suspended growth systems. In addition, the highest titers in literature so far were achieved in the TRB. 16S rRNA analysis was performed showing Clostridium and Rummenliibacillus to be the key genus for the efficient process at pH 6. Finally, the experimental methodology followed, and data collected proved the robustness of mixed culture biofilm reactors in respect to pH changes, as the same reactor performance and bacterial community were achieved regardless of the operation history.
AB - Syngas fermentation allows for the conversion of wastes into useful commodity chemicals. To target higher value products, the conditions can be tuned to be favourable for both acetogenic and reverse beta-oxidation pathways and produce, in one stage, butyric and caproic acid. Studies in CSTR have shown the crucial role of pH, which must be low enough to allow for ethanol generation in the acetogenic step while avoiding the inhibition of reverse β-oxidation in acidic conditions. However, no studies have investigated the effect of pH in reactor configurations suitable for syngas fermentation (i.e., allowing for cell retention and exhibiting high mass transfer rates at low operating costs), such as Trickle Bed Reactors, TBR. In this study, two TBR were used to study the pH effect on the fermentation of syngas to produce C4 and C6 acids, using undefined mixed cultures. Five pH values were tested in the range 4.5–7.5, and pH 6 was found to be the most favourable for simultaneous production of C4 & C6 acids from syngas, which agrees with what was found in suspended growth systems. In addition, the highest titers in literature so far were achieved in the TRB. 16S rRNA analysis was performed showing Clostridium and Rummenliibacillus to be the key genus for the efficient process at pH 6. Finally, the experimental methodology followed, and data collected proved the robustness of mixed culture biofilm reactors in respect to pH changes, as the same reactor performance and bacterial community were achieved regardless of the operation history.
KW - Butyric acid
KW - Caproic acid
KW - Chain elongation
KW - Reverse beta oxidation
KW - Syngas fermentation
KW - Trickle bed reactor
U2 - 10.1016/j.biombioe.2024.107292
DO - 10.1016/j.biombioe.2024.107292
M3 - Journal article
AN - SCOPUS:85197061686
SN - 0961-9534
VL - 187
JO - Biomass and Bioenergy
JF - Biomass and Bioenergy
M1 - 107292
ER -