• Breakthrough bioprocess turns CO<sub>2 </sub>and electricity into high-protein food
    A hybrid bioreactor integrating anaerobic and aerobic processes for converting CO2 and electricity into single-cell protein. Picture: Courtesy of the authors

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Breakthrough bioprocess turns CO2 and electricity into high-protein food

A pioneering study published in Environmental Science and Ecotechnology has unveiled a novel bioprocess that transforms carbon dioxide (CO2) and electricity into single-cell protein (SCP), a sustainable and nutrient-rich food source. Developed by researchers from Xi’an Jiaotong University and the Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, this innovative system combines anaerobic and aerobic microbial processes to efficiently produce SCP using acetate as a key intermediate.

The system consists of two interconnected reactors: the first uses microbial electrosynthesis (MES) to convert CO2 into acetate, while the second employs aerobic bacteria – alcaligenes – to upgrade acetate into SCP. By recirculating the medium between the reactors, the team achieved a remarkable cell dry weight of 17.4 g/L, with a protein content of 74% – surpassing traditional protein sources like fish and soybean meal. The process also minimizes pH adjustment, reduces wastewater generation, and alleviates product inhibition, enhancing both sustainability and efficiency.

This breakthrough offers a promising solution to global food security and climate challenges by converting CO2 into valuable protein. The SCP produced is rich in essential amino acids, making it an excellent supplement for animal feed and a potential candidate for human nutrition.

As global food demand rises and climate change intensifies, this technology represents a significant step toward a circular carbon economy, turning greenhouse gases into nutritious food while reducing environmental impact. The study underscores the potential of biohybrid systems to revolutionize sustainable food production and address pressing environmental issues.



The full article has been made available by its authors, Kun Guo et al, as open access under a Creative Commons license.

Single-Cell Protein Production from CO2 and Electricity with A Recirculating Anaerobic-Aerobic Bioprocess

Highlights

  • A hybrid bioreactor integrating anaerobic and aerobic processes is developed for converting CO2 and electricity into single-cell protein (SCP).
  • The system facilitates collaboration between anaerobic Acetobacterium and aerobic Alcaligenes.
  • Efficient SCP production from CO2 is achieved using acetate as the intermediate metabolite.
  • The reactor design mitigates product inhibition, reduces base consumption, and minimizes wastewater generation.

Abstract

Microbial electrosynthesis (MES) represents a promising approach for converting CO2 into organic chemicals. However, its industrial application is hindered by low-value products, such as acetate and methane, and insufficient productivity. To address these limitations, coupling acetate production via MES with microbial upgrading to higher-value compounds offers a viable solution. Here we show an integrated reactor that recirculates a cell-free medium between an MES reactor, hosting anaerobic homoacetogens (Acetobacterium), and a continuously stirred tank bioreactor, hosting aerobic acetate-utilizing bacteria (Alcaligenes), for efficient single-cell protein (SCP) production from CO₂ and electricity. The reactor achieved a maximum cell dry weight (CDW) of 17.4 g L-1, with an average production rate of 1.5 g L-1 d-1. The protein content of the biomass reached 74% of the dry weight. Moreover, the integrated design significantly reduced wastewater generation, mitigated product inhibition, and enhanced SCP production. These results demonstrate the potential of this integrated reactor for the efficient and sustainable production of high value bioproducts from CO2 and electricity using acetate as a key intermediate.

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