Thermodynamic Constraints on Electromicrobial Protein Production

Abstract

Global consumption of protein is projected to double by the middle of the 21st century. However, protein production is one of the most energy intensive and environmentally damaging parts of the food supply system today. Electromicrobial production technologies that combine renewable electricity and CO2-fixing microbial metabolism could dramatically increase the energy efficiency of commodity chemical production. Here we present a molecular-scale model that sets an upper limit on the performance of any organism performing electromicrobial protein production. We show that engineered microbes that fix CO2 and N2 using reducing equivalents produced by H2-oxidation or extracellular electron uptake could produce amino acids with energy inputs as low as 64 MJ kg−1, approximately one order of magnitude higher than any previous estimate of the efficiency of electromicrobial protein production. This work provides a roadmap for development of engineered microbes that could significantly expand access to proteins produced with a low environmental footprint.

Practical and thermodynamic constraints on electromicrobially accelerated CO2 mineralization

“…EMP technologies use specialized microorganisms that can absorb electricity (preferably renewable) into their metabolism to power CO 2 fixation and the subsequent enzymatic production of chemicals. In theory, EMP could produce any compound that can be synthesized biologically, but we believe its most promising application is in the production of extremely high-volume, but low-cost chemicals such as biofuels ( Salimijazi et al., 2020 ) and proteins ( Leger et al., 2021 ; Wise et al., 2022 ).…”

“…However, at the time of writing EMP technologies are nascent, and difficult to implement even at lab scale. Our theoretical analyses of EMP ( Salimijazi et al., 2020 ; Wise et al., 2022 ) are allowing us to assess which opportunities are the most fruitful to pursue and build support for pursuing them.…”

Efficiency Estimates for Electromicrobial Production of Branched-chain Hydrocarbons

“…In this work we extend our earlier predictions of electromicrobial production efficiency 4,8,25,26 to make minimum energy cost and upper-limit production efficiency estimates of single-and multi-branched hydrocarbons powered by H2-oxidation 18,19 or EEU 8,21,22 , with carbon supplied by in vivo CO2-fixation with the Calvin cycle. We then calculate the production efficiency of drop-in fuel blends of increasing branchedchain content.…”

“…Meanwhile, theoretical predictions indicate that the efficiency of EMP could exceed all forms of photosynthesis 7,8,[24][25][26] . This high efficiency mitigates many of the concerns about competition for land created by first-and second-generation biofuels 27,28 .…”

Living electronics: A catalogue of engineered living electronic components

“…In the case of electrofermentation, cells are grown in the presence of an anode to facilitate the recycling of intracellular reduced cofactors resulting in shifts in the fermentative products generated and allowing for unbalanced fermentation pathways (Askitosari et al, 2019 ; Bursac et al, 2017 ; Förster et al, 2017 ; Tejedor‐Sanz et al, 2022 ; TerAvest et al, 2014 ). Recently, there has also been an interest in both electrosynthesis and electrofermentation to control microbial‐based food production (Tejedor‐Sanz et al, 2022 ; Wise et al, 2022 ). The extensive use of microbes in both chemical and food production makes this particular type of electrical bioactuation particularly exciting.…”