Medium-chain carboxylic acids production using consortia from winery wastewater, ruminal fluid and granular sludge

Environmental pressures caused by population growth and consumerism require the development of resource recovery from waste, hence a circular economy approach. The production of chemicals and fuels from organic waste using mixed microbial cultures (MMC) has become promising. MMC use the synergy of bio-catalytic activities from different microorganisms to transform complex organic feedstock, such as by-products from food production and food waste. In the absence of oxygen, the feedstock can be converted into biogas through the established anaerobic digestion (AD) approach. The potential of MMC has shifted to production of intermediate AD compounds as precursors for renewable chemicals. A particular set of anaerobic pathways in MMC fermentation, known as chain elongation, can occur under specific conditions producing medium chain carboxylic acids (MCCAs) with higher value than biogas and broader applicability. This review introduces the chain elongation pathway and other bio-reactions occurring during MMC fermentation. We present an overview of the complex feedstocks used, and pinpoint the main operational parameters for MCCAs production such as temperature, pH, loading rates, inoculum, head space composition, and reactor design. The review evaluates the key findings of MCCA production using MMC, and concludes by identifying critical research targets to drive forward this promising technology as a valorisation method for complex organic waste.

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Insights into the microbiomes for medium-chain carboxylic acids production from biowastes through chain elongation

Critical Reviews in Environmental Science and Technology ◽

10.1080/10643389.2021.1957342 ◽

2021 ◽

pp. 1-26

Author(s):

Xingdong Shi ◽

Lan Wu ◽

Wei Wei ◽

Bing-Jie Ni

Keyword(s):

Carboxylic Acids ◽

Chain Elongation ◽

Medium Chain

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Machine learning-assisted identification of bioindicators predicts medium-chain carboxylate production performance of an anaerobic mixed culture

International Chain Elongation Conference 2020 ◽

10.18174/icec2020.18013 ◽

2020 ◽

Author(s):

Bin Liu

Keyword(s):

Machine Learning ◽

Mixed Culture ◽

Production Performance ◽

Chain Elongation ◽

Medium Chain ◽

The Right

Contribution to the International Chain Elongation Conference 2020 | ICEC 2020. An abstract can be found in the right column.

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Long-Term Continuous Extraction of Medium-Chain Carboxylates by Pertraction With Submerged Hollow-Fiber Membranes

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2021.726946 ◽

2021 ◽

Vol 9 ◽

Author(s):

Jiajie Xu ◽

Bin Bian ◽

Largus T. Angenent ◽

Pascal E. Saikaly

Keyword(s):

Partial Pressure ◽

Carboxylic Acids ◽

Hollow Fiber ◽

Operating Conditions ◽

Extraction Rate ◽

Chain Elongation ◽

Hollow Fiber Membranes ◽

Small Surface ◽

Medium Chain ◽

Fiber Membranes

Medium-chain carboxylic acids (MCCAs), which can be generated from organic waste and agro-industrial side streams through microbial chain elongation, are valuable chemicals with numerous industrial applications. Membrane-based liquid-liquid extraction (pertraction) as a downstream separation process to extract MCCAs has been applied successfully. Here, a novel pertraction system with submerged hollow-fiber membranes in the fermentation bioreactor was applied to increase the MCCA extraction rate and reduce the footprint. The highest average surface-corrected MCCA extraction rate of 655.2 ± 86.4 mmol C m−2 d−1 was obtained, which was higher than any other previous reports, albeit the relatively small surface area removed only 11.6% of the introduced carbon via pertraction. This submerged extraction system was able to continuously extract MCCAs with a high extraction rate for more than 8 months. The average extraction rate of MCCA by internal membrane was 3.0- to 4.7-fold higher than the external pertraction (traditional pertraction) in the same bioreactor. A broth upflow velocity of 7.6 m h−1 was more efficient to extract MCCAs when compared to periodic biogas recirculation operation as a means to prevent membrane fouling. An even higher broth upflow velocity of 40.5 m h−1 resulted in a significant increase in methane production, losing more than 30% of carbon conversion to methane due to a loss of H2, and a subsequent drop in the H2 partial pressure. This resulted in the shift from a microbial community with chain elongators as the key functional group to methanogens, because the drop in H2 partial pressure led to thermodynamic conditions that oxidizes ethanol and carboxylic acids to acetate and H2 with methanogens as the syntrophic partner. Thus, operators of chain elongating systems should monitor the H2 partial pressure when changes in operating conditions are made.

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Direct medium-chain carboxylic-acid oil separation by an Electrodialysis/phase separation

International Chain Elongation Conference 2020 ◽

10.18174/icec2020.18005 ◽

2020 ◽

Author(s):

Jiajie Xu

Keyword(s):

Phase Separation ◽

Carboxylic Acid ◽

Chain Elongation ◽

Oil Separation ◽

Acid Oil ◽

Medium Chain ◽

The Right

Contribution to the International Chain Elongation Conference 2020 | ICEC 2020. An abstract can be found in the right column.

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