Isobutyrate biosynthesis via methanol chain elongation: converting organic wastes to platform chemicals

Abstract

BACKGROUND Isobutyrate is a platform chemical that is currently produced from a non‐renewable fossil‐based feedstock. This study aimed at developing a renewable isobutyrate production process by using methanol chain elongation, a novel bioprocess that uses organic waste as primary feedstocks and an undefined reactor microbiome as the catalyst. RESULTS A continuous anaerobic bioreactor experiment was first performed using a synthetic medium containing acetate, butyrate and methanol, all of which are common derivatives from organic residues. Continuous isobutyrate (2.0 g L−1 day−1) and caproate formation (0.2 g L−1 day−1) from methanol, acetate and butyrate were demonstrated. A batch test to synthesise isobutyrate from a real organic waste, i.e. acidified supermarket waste (ASW), was performed. Up to 6.2 g L−1 isobutyrate was formed which accounted for 63% of all identified products. CONCLUSION In this study, a proof‐of‐principle for isobutyrate production from organic waste via methanol chain elongation was demonstrated. The continuous accumulation or supply of butyrate, the suppression of methanogenic activity and methanol addition were shown to be of use to provide conditions for isobutyrate formation. © 2016 Society of Chemical Industry

Lactate-based microbial chain elongation for n-caproate and iso-butyrate production: genomic and metabolic features of three novel Clostridia isolates

“…As this isomerization step does not release any free energy, another possible explanation is that bacteria try to overcome inhibition effects of the accumulated nbutyrate, because the corresponding fatty acid of the unbranched form is more toxic than the branched form. As suggested for a methanol-based chain elongation system [3,12], the formation of iso-butyrate may facilitate bacteria to further obtain energy from the chain elongation process.…”

“…Currently, iso-butyrate is manufactured by acid-catalyzed Koch carbonylation of propylene, which is derived from fossil feedstock [2]. Microbial production of iso-butyrate from organic wastes or biomass residues is a more sustainable alternative, which has been demonstrated by recent studies [12,13].…”

“…However, insu cient knowledge has been generated yet on the physiology of lactate-based chain elongation from pure culture studies, and there is a lack of genome-level information to explore the genetic characteristics shared by chain-elongating bacteria. Previous studies have shown that iso-butyrate can be produced in methanol-based chain elongation [3,12,13]. The results suggested that Clostridium luticellarii might be responsible for the iso-butyrate formation during mixed culture fermentation, which was further tested by pure culture study of C. luticellarii, showing its ability to convert acetate and methanol to isobutyrate [16].…”

Control strategies for ethanol-based chain elongation processes

“…Hydrolysis and acidogenesis of food waste was executed in a batch reactor with a working volume of 20 L as described by [92]. A er loading 20 L diluted food waste into the reactor, the reactor content was sparged with N 2 for 10 min to remove oxygen.…”

“…Alternatively, syngas can be converted into methanol [120], ethanol and propanol [121] which are all suitable electron donors. However, although methanol-based chain elongation is not optimised and typically results in low MCFA production rates (≤ 0.23 g/L/d) and selectivities (≤ 8 % on an electron basis), it could be used for the production of isobutyrate [33] [92].…”