Formate-induced CO tolerance and methanogenesis inhibition in fermentation of syngas and plant biomass for carboxylate production

Biotechnology for Biofuels and Bioproducts

Research

Heike Sträuber¹  Sabine Kleinsteuber¹  Flávio C. F. Baleeiro²  Anke Neumann³  Lukas Varchmin³ 

[1] Department of Environmental Microbiology, Helmholtz Centre for Environmental Research – UFZ, Leipzig, Germany;Department of Environmental Microbiology, Helmholtz Centre for Environmental Research – UFZ, Leipzig, Germany;Technical Biology, Institute of Process Engineering in Life Science, Karlsruhe Institute of Technology – KIT, Karlsruhe, Germany;Technical Biology, Institute of Process Engineering in Life Science, Karlsruhe Institute of Technology – KIT, Karlsruhe, Germany;

关键词: Mixotrophy;    Volatile fatty acids;    Medium-chain carboxylic acids;    Formic acid;    Chain elongation;    Microbiome;    Carbon monoxide;    Ethene;    Hexanoic acid;    Lactic acid bacteria;   

DOI  :  10.1186/s13068-023-02271-w

 received in 2022-07-01, accepted in 2023-01-29,  发布年份 2023

来源: Springer

【 摘 要 】

BackgroundProduction of monocarboxylates using microbial communities is highly dependent on local and degradable biomass feedstocks. Syngas or different mixtures of H2, CO, and CO2 can be sourced from biomass gasification, excess renewable electricity, industrial off-gases, and carbon capture plants and co-fed to a fermenter to alleviate dependence on local biomass. To understand the effects of adding these gases during anaerobic fermentation of plant biomass, a series of batch experiments was carried out with different syngas compositions and corn silage (pH 6.0, 32 °C).ResultsCo-fermentation of syngas with corn silage increased the overall carboxylate yield per gram of volatile solids (VS) by up to 29% (0.47 ± 0.07 g gVS−1; in comparison to 0.37 ± 0.02 g gVS−1 with a N2/CO2 headspace), despite slowing down biomass degradation. Ethylene and CO exerted a synergistic effect in preventing methanogenesis, leading to net carbon fixation. Less than 12% of the electrons were misrouted to CH4 when either 15 kPa CO or 5 kPa CO + 1.5 kPa ethylene was used. CO increased the selectivity to acetate and propionate, which accounted for 85% (electron equivalents) of all products at 49 kPa CO, by favoring lactic acid bacteria and actinobacteria over n-butyrate and n-caproate producers. Inhibition of n-butyrate and n-caproate production by CO happened even when an inoculum preacclimatized to syngas and lactate was used. Intriguingly, the effect of CO on n-butyrate and n-caproate production was reversed when formate was present in the broth.ConclusionsThe concept of co-fermenting syngas and plant biomass shows promise in three aspects: by making anaerobic fermentation a carbon-fixing process, by increasing the yields of short-chain carboxylates (propionate and acetate), and by minimizing electron losses to CH4. Moreover, a model was proposed for how formate can alleviate CO inhibition in certain acidogenic bacteria. Testing the fermentation of syngas and plant biomass in a continuous process could potentially improve selectivity to n-butyrate and n-caproate by enriching chain-elongating bacteria adapted to CO and complex biomass.

【 授权许可】

CC BY   
© The Author(s) 2023

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