Syngas-aided anaerobic fermentation for medium-chain carboxylate and alcohol production: the case for microbial communities

Baleeiro, Flávio C. F.; Kleinsteuber, Sabine; Neumann, Anke; Sträuber, Heike

doi:10.1007/s00253-019-10086-9

Cited by 45 publications

(42 citation statements)

References 128 publications

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“…During the upscaling process, lessons learned from syngas fermentation research can be useful to tackle the challenges of feeding H 2 as a substrate, such as micro-sparging to overcome low gas-mass transfer rates and using bubble-column reactors to keep power input low (Takors et al, 2018). Moreover, at industrial scale, renewable H 2 is ideally sourced from water hydrolysis fueled by renewable energy or from lignocellulose gasification (Baleeiro et al, 2019).…”

Section: Enhancing Caproate Productionmentioning

confidence: 99%

“…Among the proposed solutions to overcome ED scarcity in MCC production, integration of CE with syngas fermentation has been proposed in several different configurations (Baleeiro et al, 2019), thus applying H 2 and CO as alternative EDs for CE. Syngas (H 2 /CO 2 /CO) and water-gas shifted syngas (H 2 /CO 2 ) can be produced by gasification of lignocellulosic biomass, making even the most recalcitrant fractions of lignocellulose bioavailable to anaerobic bacteria via the Wood-Ljungdahl pathway.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities

Baleeiro

Kleinsteuber

Sträuber

2021

Front. Bioeng. Biotechnol.

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Electron donor scarcity is seen as one of the major issues limiting economic production of medium-chain carboxylates from waste streams. Previous studies suggest that co-fermentation of hydrogen in microbial communities that realize chain elongation relieves this limitation. To better understand how hydrogen co-feeding can support chain elongation, we enriched three different microbial communities from anaerobic reactors (A, B, and C with ascending levels of diversity) for their ability to produce medium-chain carboxylates from conventional electron donors (lactate or ethanol) or from hydrogen. In the presence of abundant acetate and CO2, the effects of different abiotic parameters (pH values in acidic to neutral range, initial acetate concentration, and presence of chemical methanogenesis inhibitors) were tested along with the enrichment. The presence of hydrogen facilitated production of butyrate by all communities and improved production of i-butyrate and caproate by the two most diverse communities (B and C), accompanied by consumption of acetate, hydrogen, and lactate/ethanol (when available). Under optimal conditions, hydrogen increased the selectivity of conventional electron donors to caproate from 0.23 ± 0.01 mol e–/mol e– to 0.67 ± 0.15 mol e–/mol e– with a peak caproate concentration of 4.0 g L–1. As a trade-off, the best-performing communities also showed hydrogenotrophic methanogenesis activity by Methanobacterium even at high concentrations of undissociated acetic acid of 2.9 g L–1 and at low pH of 4.8. According to 16S rRNA amplicon sequencing, the suspected caproate producers were assigned to the family Anaerovoracaceae (Peptostreptococcales) and the genera Megasphaera (99.8% similarity to M. elsdenii), Caproiciproducens, and Clostridium sensu stricto 12 (97–100% similarity to C. luticellarii). Non-methanogenic hydrogen consumption correlated to the abundance of Clostridium sensu stricto 12 taxa (p < 0.01). If a robust methanogenesis inhibition strategy can be found, hydrogen co-feeding along with conventional electron donors can greatly improve selectivity to caproate in complex communities. The lessons learned can help design continuous hydrogen-aided chain elongation bioprocesses.

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Section: Enhancing Caproate Productionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities

Baleeiro

Kleinsteuber

Sträuber

2021

Front. Bioeng. Biotechnol.

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“…To estimate costs for acquiring ethylene, an approximate price of 1 US$ kg −1 was considered 26 and a continuous loss of 1% of the flow of ethylene was assumed. For electricity consumption by gas recirculation, an efficiency of 90% of an isentropic compressor with an inlet gas pressure of 1.0 bar a and an electricity price of 0.12 US$ kWh −1 was assumed 5 . For the mixture of H 2 /CO 2 /ethylene, a gas mixture with 78.5% H 2 , 20% CO 2 , and 1.5% ethylene was considered.…”

Section: Methodsmentioning

confidence: 99%

“…An HRT of 14 days was considered. For the range of values of the carboxylate broth, an average price of carboxylates of 2 US$ kg −1 and an extractable amount of carboxylates between 4 g L −1 (lowest broth value) and 20 g L −1 (highest broth value) 5 was assumed. Other operating costs of the process, such as power input for stirring, consumption of other chemicals, and downstream processing, were not considered.…”

Section: Methodsmentioning

confidence: 99%

Recirculation of H₂, CO₂, and ethylene improves carbon fixation and carboxylate yields in anaerobic fermentation

Baleeiro

Kleinsteuber

Sträuber

2021

Preprint

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Anaerobic fermentation with mixed cultures has gained momentum as a bioprocess for its promise to produce platform carboxylates from low-value biomass feedstocks. Anaerobic fermenters are net carbon emitters and their carboxylate yields are limited by electron donor availability. In a new approach to tackle these two disadvantages, we operated two bioreactors fed with acetate and lactate as a model feedstock while recirculating H2/CO2 to stimulate concomitant autotrophic activity. After 42 days of operation, hydrogenotrophic methanogenesis was predominant and ethylene (≥1.3 kPa) was added to one of the reactors, inhibiting methanogenesis completely and recovering net carbon fixation (0.20 g CO2 L-1 d-1). When methanogenesis was inhibited, exogenous H2 accounted for 17% of the consumed electron donors. Lactate-to-butyrate selectivity was 101% (88% in the control without ethylene) and lactate-to-caproate selectivity was 17% (2.3% in the control). Community analysis revealed that ethylene caused Methanobacterium to be washed out, giving room to acetogenic bacteria. In contrast to 2-bromoethanosulfonate, ethylene is a scalable methanogenesis inhibition strategy that did not collaterally block i-butyrate formation. By favoring the bacterial share of the community to become mixotrophic, the concept offers a way to simultaneously increase selectivity to medium-chain carboxylates and to develop a carbon-fixing chain elongation process.

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“…By merging the syngas platform with the carboxylate platform, i.e., combining syngas fermentation with fermentation of organic substrate, dry and moist or liquid biomass can be integrated in an optimal way. Thereby, MCC product yields and productivities are increased and product portfolios can even be expanded to bioalcohols (Baleeiro et al, 2019;Chowdhury et al, 2019).…”

Section: Cascading Use Of Organic Residues For Carboxylates Bioplastmentioning

confidence: 99%

Beyond Sugar and Ethanol Production: Value Generation Opportunities Through Sugarcane Residues

et al. 2020

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Sugarcane is the most produced agricultural commodity in tropical and subtropical regions, where it is primarily used for the production of sugar and ethanol. The latter is mostly used to produce alcoholic beverages as well as low carbon biofuel. Despite well-established production chains, their respective residues and by-products present unexploited potentials for further product portfolio diversification. These fully or partially untapped product streams are a) sugarcane trash or straw that usually remain on the fields after mechanized harvest, b) ashes derived from bagasse combustion in cogeneration plants, c) filter cake from clarification of the sugarcane juice, d) vinasse which is the liquid residue after distillation of ethanol, and e) biogenic CO2 emitted during bagasse combustion and ethanol fermentation. The development of innovative cascading processes using these residual biomass fractions could significantly reduce final disposal costs, improve the energy output, reduce greenhouse gas emissions, and extend the product portfolio of sugarcane mills. This study reviews not only the state-of-the-art sugarcane biorefinery concepts, but also proposes innovative ways for further valorizing residual biomass. This study is therefore structured in four main areas, namely: i) Cascading use of organic residues for carboxylates, bioplastic, and bio-fertilizer production, ii) recovery of unexploited organic residues via anaerobic digestion to produce biogas, iii) valorization of biogenic CO2 sources, and iv) recovery of silicon from bagasse ashes.

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Syngas-aided anaerobic fermentation for medium-chain carboxylate and alcohol production: the case for microbial communities

Cited by 45 publications

References 128 publications

Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities

Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities

Recirculation of H₂, CO₂, and ethylene improves carbon fixation and carboxylate yields in anaerobic fermentation

Beyond Sugar and Ethanol Production: Value Generation Opportunities Through Sugarcane Residues

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Syngas-aided anaerobic fermentation for medium-chain carboxylate and alcohol production: the case for microbial communities

Cited by 45 publications

References 128 publications

Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities

Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities

Recirculation of H2, CO2, and ethylene improves carbon fixation and carboxylate yields in anaerobic fermentation

Beyond Sugar and Ethanol Production: Value Generation Opportunities Through Sugarcane Residues

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Recirculation of H₂, CO₂, and ethylene improves carbon fixation and carboxylate yields in anaerobic fermentation