Dataset Information

Propionate Production by Bioelectrochemically-Assisted Lactate Fermentation and Simultaneous CO₂ Recycling.

ABSTRACT: Production of volatile fatty acids (VFAs), fundamental building blocks for the chemical industry, depends on fossil fuels but organic waste is an emerging alternative substrate. Lactate produced from sugar-containing waste streams can be further processed to VFAs. In this study, electrofermentation (EF) in a two-chamber cell is proposed to enhance propionate production via lactate fermentation. At an initial pH of 5, an applied potential of -1 V vs. Ag/AgCl favored propionate production over butyrate from 20 mM lactate (with respect to non-electrochemical control incubations), due to the pH buffering effect of the cathode electrode, with production rates up to 5.9 mM d^-1 (0.44 g L^-1 d^-1). Microbial community analysis confirmed the enrichment of propionate-producing microorganisms, such as Tyzzerella sp. and Propionibacterium sp. Organisms commonly found in microbial electrosynthesis reactors, such as Desulfovibrio sp. and Acetobacterium sp., were also abundant at the cathode, indicating their involvement in recycling CO₂ produced by lactate fermentation into acetate, as confirmed by stoichiometric calculations. Propionate was the main product of lactate fermentation at substrate concentrations up to 150 mM, with a highest production rate of 12.9 mM d^-1 (0.96 g L^-1 d^-1) and a yield of 0.48 mol mol^-1 lactate consumed. Furthermore, as high as 81% of the lactate consumed (in terms of carbon) was recovered as soluble product, highlighting the potential for EF application with high-carbon waste streams, such as cheese whey or other food wastes. In summary, EF can be applied to control lactate fermentation toward propionate production and to recycle the resulting CO₂ into acetate, increasing the VFA yield and avoiding carbon emissions and addition of chemicals for pH control.

SUBMITTER: Isipato M

PROVIDER: S-EPMC7769879 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Propionate Production by Bioelectrochemically-Assisted Lactate Fermentation and Simultaneous CO<sub>2</sub> Recycling.

Isipato Marco M Dessì Paolo P Sánchez Carlos C Mills Simon S Ijaz Umer Z UZ Asunis Fabiano F Spiga Daniela D De Gioannis Giorgia G Mascia Michele M Collins Gavin G Muntoni Aldo A Lens Piet N L PNL

Frontiers in microbiology 20201215

Production of volatile fatty acids (VFAs), fundamental building blocks for the chemical industry, depends on fossil fuels but organic waste is an emerging alternative substrate. Lactate produced from sugar-containing waste streams can be further processed to VFAs. In this study, electrofermentation (EF) in a two-chamber cell is proposed to enhance propionate production <i>via</i> lactate fermentation. At an initial pH of 5, an applied potential of -1 V vs. Ag/AgCl favored propionate production o ...[more]

PMID: 33384675

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Project description:BackgroundConsiderable progress is being made in ethanol production from lignocellulosic feedstocks by fermentation, but negative effects of inhibitors on fermenting microorganisms are still challenging. Feeding preadapted cells has shown positive effects by sustaining fermentation in high-gravity simultaneous saccharification and co-fermentation (SSCF). Loss of cell viability has been reported in several SSCF studies on different substrates and seems to be the main reason for the declining ethanol production toward the end of the process. Here, we investigate how the combination of yeast preadaptation and feeding, cell flocculation, and temperature reduction improves the cell viability in SSCF of steam pretreated wheat straw.ResultsMore than 50% cell viability was lost during the first 24 h of high-gravity SSCF. No beneficial effects of adding selected nutrients were observed in shake flask SSCF. Ethanol concentrations greater than 50 g L-1 led to significant loss of viability and prevented further fermentation in SSCF. The benefits of feeding preadapted yeast cells were marginal at later stages of SSCF. Yeast flocculation did not improve the viability but simplified cell harvest and improved the feasibility of the cell feeding strategy in demo scale. Cultivation at 30 °C instead of 35 °C increased cell survival significantly on solid media containing ethanol and inhibitors. Similarly, in multifeed SSCF, cells maintained the viability and fermentation capacity when the temperature was reduced from 35 to 30 °C during the process, but hydrolysis yields were compromised. By combining the yeast feeding and temperature change, an ethanol concentration of 65 g L-1, equivalent to 70% of the theoretical yield, was obtained in multifeed SSCF on pretreated wheat straw. In demo scale, the process with flocculating yeast and temperature profile resulted in 5% (w/w) ethanol, equivalent to 53% of the theoretical yield.ConclusionsMultifeed SSCF was further developed by means of a flocculating yeast and a temperature-reduction profile. Ethanol toxicity is intensified in the presence of lignocellulosic inhibitors at temperatures that are beneficial to hydrolysis in high-gravity SSCF. The counteracting effects of temperature on cell viability and hydrolysis call for more tolerant microorganisms, enzyme systems with lower temperature optimum, or full optimization of the multifeed strategy with temperature profile.

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Propionate Production by Bioelectrochemically-Assisted Lactate Fermentation and Simultaneous CO₂ Recycling.

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Propionate Production by Bioelectrochemically-Assisted Lactate Fermentation and Simultaneous CO<sub>2</sub> Recycling.

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Propionate Production by Bioelectrochemically-Assisted Lactate Fermentation and Simultaneous CO2 Recycling.

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Propionate Production by Bioelectrochemically-Assisted Lactate Fermentation and Simultaneous CO<sub>2</sub> Recycling.

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OmicsDI is part of the ELIXIR infrastructure

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Propionate Production by Bioelectrochemically-Assisted Lactate Fermentation and Simultaneous CO₂ Recycling.