Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate

Abstract

Volatile fatty acids (VFAs) can be readily produced from many anaerobic microbes and subsequently utilized as precursors to renewable biofuels and biochemicals. Megasphaera elsdenii represents a promising host for production of VFAs, butyric acid (BA) and hexanoic acid (HA). However, due to the toxicity of these acids, product removal via an extractive fermentation system is required to achieve high titers and productivities. Here, we examine multiple aspects of extractive separations to produce BA and HA from glucose and lignocellulosic hydrolysate with M. elsdenii. A mixture of oleyl alcohol and 10% (v/v) trioctylamine was selected as an extraction solvent due to its insignificant inhibitory effect on the bacteria. Batch extractive fermentations were conducted in the pH range of 5.0 to 6.5 to select the best cell growth rate and extraction efficiency combination. Subsequently, fed-batch pertractive fermentations were run over 230 h, demonstrating high BA and HA concentrations in the extracted fraction (57.2 g/L from~190 g/L glucose) and productivity (0.26 g/L/h). To our knowledge, these are the highest combined acid titers and productivity values reported for M. elsdenii and bacterial mono-cultures from sugars. Lastly, the production of BA and HA (up to 17 g/L) from lignocellulosic sugars was demonstrated.

Biochemical Production and Separation of Carboxylic Acids for Biorefinery Applications

“…This study showed that in the absence of pertraction but with amines included, the extraction efficiency only increased by 1.4-fold, while with pertraction the increase was significantly higher. In another study with in situ separation using pertraction, butyric acid and hexanoic acid productivity was found to increase by at least 3-fold while using pertractive fermentation when compared to batch fermentation [141]. These studies indicated that oleyl alcohol with trioctylamine as the extractant was found to be less inhibitory to the microbial culture during pertractive fermentation when compared to octanol-trihexylamine extractant.…”

Multi-omic analysis of medium-chain fatty acid synthesis byCandidatusWeimerbacter bifidus, gen. nov., sp. nov., andCandidatusPseudoramibacter fermentans, sp. nov.

“…P. fermentans LDH clusters with proteins from organisms that consume lactate anaerobically ( Fig. 11 ), including two bacteria known to convert lactate to MCFA, Ruminococcaeae CPB6 and Megasphaera elsdenii (5, 7), and with the LDH from A. woodii that uses electron confurcation to couple lactate and ferredoxin oxidation with NAD + reduction to overcome the thermodynamic bottleneck of lactate oxidation (27). Pairwise correlation analyses of transcript abundance ( Fig.…”

Organic phase screening for in‐stream reactive extraction of bio‐based 3‐hydroxypropionic acid: biocompatibility and extraction performances

“…In situ extraction occurs with a direct contact between the cells and the extraction phase: (a) two‐phase partitioning bioreactors or (b) solvent‐impregnated particles dispersed in bioconversion medium or with an indirect contact: (c) using immobilized cells in the bioconversion broth; or (d) using membrane‐based extraction inside the bioreactor . In‐stream extraction occurs with direct contact: (e) pumping bioconversion broth to a column packed with solvent‐impregnated particles or indirect contact: (f) membrane‐based extraction outside the bioreactor; or (g) introducing a microfiltration unit to separate the biocatalyst from broth before contact …”

“…18,19 In-stream extraction occurs with direct contact: (e) pumping bioconversion broth to a column packed with solvent-impregnated particles 20 or indirect contact: (f ) membrane-based extraction outside the bioreactor 21,22 ; or (g) introducing a microfiltration unit to separate the biocatalyst from broth before contact. 23,24 accumulation in the medium can be avoided by progressively supplying glycerol. 7 This pathway has the advantage that no other by-products are present, which simplifies further purification of the desired product.…”