One-step production of C6–C8 carboxylates by mixed culture solely grown on CO

Abstract

BackgroundThis study aimed at producing C6–C8 medium-chain carboxylates (MCCAs) directly from gaseous CO using mixed culture. The yield and C2–C8 product composition were investigated when CO was continuously fed with gradually increasing partial pressure.ResultsThe maximal concentrations of n-caproate, n-heptylate, and n-caprylate were 1.892, 1.635, and 1.033 mmol L−1, which were achieved at the maximal production rates of 0.276, 0.442, and 0.112 mmol L−1 day−1, respectively. Microbial analysis revealed that long-term acclimation and high CO partial pressure were important to establish a CO-tolerant and CO-utilizing chain-elongating microbiome, rich in Acinetobacter, Alcaligenes, and Rhodobacteraceae and capable of forming MCCAs solely from CO.ConclusionsThese results demonstrated that carboxylate and syngas platform could be integrated in a shared growth vessel, and could be a promising one-step technique to convert gaseous syngas to preferable liquid biochemicals, thereby avoiding the necessity to coordinate syngas fermentation to short-chain carboxylates and short-to-medium-chain elongation. Thus, this method could provide an alternative solution for the utilization of waste-derived syngas and expand the resource of promising biofuels.Electronic supplementary materialThe online version of this article (10.1186/s13068-017-1005-8) contains supplementary material, which is available to authorized users.

Metabolic Interactions of a Chain Elongation Microbiome

“…Coma et al (18) found phylotypes related to Bacteroidaceae and microorganisms or unclassified bacteria directly or indirectly involved in CCE, except for C. kluyveri. Our previous research identified one-step MCCA production from CO, which is likely realized by CO-utilizing chain-elongating microorganisms such as Alcaligenes, Acinetobacter, and Rhodobacteraceae (19). Therefore, the relationship between these unexpected, highly abundant organisms and chain elongation remains ambiguous.…”

Microbial insights of enhanced anaerobic conversion of syngas into volatile fatty acids by co-fermentation with carbohydrate-rich synthetic wastewater

“…It is worth noting that n-butyrate was detected in GS5 compared to G5 which might be related with the change of glucose/syngas metabolism pathway due to the selection of bacteria by the co-fermentation of syngas with glucose and previous studies showed that butyrate could be produced from electron donor and acetate [42][43][44]. For examples, both H 2 and CO had been reported to be as electron donors to upgrade acetate to n-butyrate [26,40]. The acetate conversion efficiency from syngas in GS5 achieved 90%, which indicated that the consumed syngas was stoichiometrically converted to acetate (Table 1).…”

“…In GS15, the acetate conversion efficiency from syngas was only 69% (Table 1), which indicated that around 30% of the consumed syngas was not converted to acetate but to other products. It was possible that high concentration of propionate compared with acetate resulted in n-valerate production by propionate with syngas in GS15, but not in GS5 [26,27]. As shown in Table 1, there was no significant difference in the glucose concentrations in the effluent of G5 and GS5 as well as G15 and GS15.…”

Modeling a co-culture ofClostridium autoethanogenumandClostridium kluyverito increase syngas conversion to medium-chain fatty-acids

“…We observe an increase of CO 2 uptake by C. kluyveri in cases where hexanoate is more abundant (see figure 4 and (see figure 7). Table 1, shows a comparison of electron yields for the hexanoate production predicted in this study compared to hexanoate production in other studies with similar culture systems [51,52,11]. Electron yield is calculated based on the amount of electrons going to hexanoate per the total amount of electrons going into the system as carbon and energy sources.…”