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This study examines the latest advancements in the field of Microbial ElectroSynthesis (MES) and reports a unique sustainability and economic assessment for the production of five alternative compounds (formic, acetic, propionic acids; methanol and ethanol). Different chemical production conditions were compared by modelling a 1000 t per year produ...
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Context 1
... further assess the sustainability of using MES technology two indicators were used, namely EG and GWR. Fig. 5 represents the EG and GWR from MES for the production of formic, acetic or propionic acids, methanol or ethanol compared to conventional routes. Industrially, acetic acid is produced by methanol carbonylation [74], formic acid through hydrolysis of methyl formate [75], propionic acid by carbonylation of ethylene [76], ethanol from ...
Context 2
... suggesting that MES processes used more carbon emissions than it produced. On the contrary, conventional methods for methanol, ethanol and formic acid production yielded positive carbon emissions. The amount of CO 2 emissions from the conventional methanol production process was twice the amount of carbon consumed when using the MES process Fig. 5. Regarding ethanol, DeCicco et al. [79] showed that using a fermentation production process emitted more CO 2 than the one used. It was shown that for a 7 year period this would result to 27% more carbon emissions than gasoline [79]. This study suggested that producing ethanol from CO 2 using MES could be more beneficial as there was ...
Citations
... These molecules can then serve as substrates in separate, intensive aerobic fermentation processes [1]. In addition to microbial fermentation of lignocellulosic residues from agriculture and forestry [3], such small molecules can be produced by gas fermentation [4], electrochemical production from CO 2 [1,5] and, potentially, from microbial electrosynthesis [6,7]. The resulting organic molecules include C 1 compounds such as formic acid and methanol as well as the C 2 compounds acetic acid and ethanol [1]. ...
Background
Elimination of greenhouse gas emissions in industrial biotechnology requires replacement of carbohydrates by alternative carbon substrates, produced from CO2 and waste streams. Ethanol is already industrially produced from agricultural residues and waste gas and is miscible with water, self-sterilizing and energy-dense. The yeast C. jadinii can grow on ethanol and has a history in the production of single-cell protein (SCP) for feed and food applications. To address a knowledge gap in quantitative physiology of C. jadinii during growth on ethanol, this study investigates growth kinetics, growth energetics, nutritional requirements, and biomass composition of C. jadinii strains in batch, chemostat and fed-batch cultures.
Results
In aerobic, ethanol-limited chemostat cultures, C. jadinii CBS 621 exhibited a maximum biomass yield on ethanol () of 0.83 gbiomass (gethanol)⁻¹ and an estimated maintenance requirement for ATP (mATP) of 2.7 mmolATP (gbiomass)⁻¹ h⁻¹. Even at specific growth rates below 0.05 h⁻¹, a stable protein content of approximately 0.54 gprotein (gbiomass)⁻¹ was observed. At low specific growth rates, up to 17% of the proteome consisted of alcohol dehydrogenase proteins, followed by aldehyde dehydrogenases and acetyl-CoA synthetase. Of 13 C. jadinii strains evaluated, 11 displayed fast growth on ethanol (μmax > 0.4 h⁻¹) in mineral medium without vitamins, and CBS 621 was found to be a thiamine auxotroph. The prototrophic strain C. jadinii CBS 5947 was grown on an inorganic salts medium in fed-batch cultures (10-L scale) fed with pure ethanol. Biomass concentrations in these cultures increased up to 100 gbiomass (kgbroth)⁻¹, with a biomass yield of 0.65 gbiomass (gethanol)⁻¹. Model-based simulation, based on quantitative parameters determined in chemostat cultures, adequately predicted biomass production. A different protein content of chemostat- and fed-batch-grown biomass (54 and 42%, respectively) may reflect the more dynamic conditions in fed-batch cultures.
Conclusions
Analysis of ethanol-grown batch, chemostat and fed-batch cultures provided a quantitative physiology baseline for fundamental and applied research on C. jadinii. Its high maximum growth rate, high energetic efficiency of ethanol dissimilation, simple nutritional requirements and high protein content, make C. jadinii a highly interesting platform for production of SCP and other products from ethanol.
... (García Martínez, Egbejimba, et al., 2021) studied the potential of electrotrophs to convert CO 2 and water into acetic acid -typically consumed as the main component of vinegar, with a caloric content of 3.49 kcal/g (Greenfield & Southgate, 2003), comparable to sugars by mass. The overall reaction for acetic acid synthesis can be described by Equation 5 (Christodoulou et al., 2017). Despite its very high energy efficiency as a calorie generation method, between~15-20% in terms of power to food when using carbon capture (Alvarado et al., 2023), this technology is severely limited for the catastrophe response application, and is not recommended over alternatives. ...
... Other study conducted by Christodoulou et al. [90] concluded that MES utilizes more carbon for one year than it produced during the synthesis of methanol, ethanol, and formic acid. Also, TEA of this study showed the economic feasibility for ethanol and formic acid production with synthesis costs of 0.88 £/kg and 0.30 £/kg, respectively; which were lesser than the market price of 1.09 £/kg and 0.38 £/kg, for the above-mentioned chemicals, respectively [90]. ...
... Other study conducted by Christodoulou et al. [90] concluded that MES utilizes more carbon for one year than it produced during the synthesis of methanol, ethanol, and formic acid. Also, TEA of this study showed the economic feasibility for ethanol and formic acid production with synthesis costs of 0.88 £/kg and 0.30 £/kg, respectively; which were lesser than the market price of 1.09 £/kg and 0.38 £/kg, for the above-mentioned chemicals, respectively [90]. Furthermore, GWP and ozone layer depletion of integrated electrochemical constructed wetland (ECW) were reported to be 69.1% and 62.1% lower than CW, respectively. ...
The world today is experiencing adverse effects of climate change due to the escalated levels of greenhouse gases such as CO2 in the atmosphere. Consequently, there is an urgent need for minimizing the CO2 level to tackle climate change. Utilization of CO2 for synthesizing valuable commodities, such as biofuel and biochemical, is an effective strategy toward mitigating climate change as well as the energy crisis. Moreover, the conversion of CO2 into valuable products is also a promising step for achieving carbon neutrality and exemplifying a circular economy. In this regard, several methods, such as physical, chemical, and biological, are available for the utilization and conversion of CO2. However, biological methods for the conversion of CO2 into biofuels and biochemicals are more sustainable as they are environmentally friendly and cost-effective compared to the chemical methods. Thus, in this chapter, different CO2 bioconversion processes with their efficacy and their limitations have been discussed. Besides this, future developments in terms of CO2 bioconversion have also been presented for alleviating the limitations, so that the production of biocommodities from CO2 can be achieved at a large scale.
... (García Martínez, Egbejimba, et al., 2021) studied the potential of electrotrophs to convert CO 2 and water into acetic acid -typically consumed as the main component of vinegar, with a caloric content of 3.49 kcal/g (Greenfield & Southgate, 2003), comparable to sugars by mass. The overall reaction for acetic acid synthesis can be described by Equation 5 (Christodoulou et al., 2017). Despite its very high energy efficiency as a calorie generation method, between ~15-20% in terms of power to food when using carbon capture (Alvarado et al., 2023), this technology is severely limited for the catastrophe response application, and is not recommended over alternatives. ...
Background: The growing human population requires consistent access to nutritious and sustainable food to thrive. To this end, non-agricultural, closed-environment food production methods can complement agriculture while increasing the resilience of the global food system to climate shocks and other risks such as biological, environmental, and trade risks, including extreme scenarios such as abrupt sunlight reduction (e.g. from a volcanic winter or nuclear winter).
Scope and Approach: This review describes the existing production processes and recent developments in non-agricultural food production, including the activities of companies carrying out established processes and of those developing innovative production processes. The potential of fermentation for production of single cell foods and for biosynthesis of key nutrients, and the nonbiological synthesis of food compounds such as from CO 2 are reviewed in depth. The study has a special focus on potential response to global catastrophic food shocks that disrupt agricultural production.
Findings and conclusions: The enormous potential for food production via key non-agricultural pathways was described and quantified. All macronutrients can be produced by both fermentation and chemical synthesis, independently from agriculture, even from CO 2. These technologies are capable of synthesizing all amino acids, as well as the essential fatty acids and multiple vitamins and micronutrients of interest. Many of these pathways are relevant industrially and resilience-wise compared to agricultural pathways due to their potential to produce at either lower cost, improved sustainability, in more extreme conditions and environments (e.g. outer space), or a combination of these. More research and resilience work is urgently needed to realize their potential.
... These limitations of physicochemical and traditional biological carbon fixation processes can be overcome by employing microbial electrosynthesis (MES), an emerging interdisciplinary technology that combines microbiology, electrochemistry, and engineering [22] . This technology has remarkable advantages in efficiently synthesizing high-value products from CO 2 or organic waste by utilizing the microbial internal metabolic pathways coupled with external energy or bioelectricity [23][24][25][26] . Therefore, MES is an efficient, environmentally friendly, and sustainable bioenergy regeneration strategy. ...
The consumption of non-renewable fossil fuels has directly contributed to a dramatic rise in global carbon dioxide (CO2) emissions, posing an ongoing threat to the ecological security of the Earth. Microbial electrosynthesis (MES) is an innovative energy regeneration strategy that offers a gentle and efficient approach to converting CO2 into high-value products. The cathode chamber is a vital component of an MES system and its internal factors play crucial roles in improving the performance of the MES system. Therefore, this review aimed to provide a detailed analysis of the key factors related to the cathode chamber in the MES system. The topics covered include inward extracellular electron transfer pathways, cathode materials, applied cathode potentials, catholyte pH, and reactor configuration. In addition, this review analyzes and discusses the challenges and promising avenues for improving the conversion of CO2 into high-value products via MES.
... Examples of PCET reactions for several alcohols and MCFAs are shown in equations 3-7 below. [143] Acetic acid : ...
Bioelectrocatalytic synthesis is the conversion of electrical energy into value‐added products using biocatalysts. These methods merge the specificity and selectivity of biocatalysis and energy‐related electrocatalysis to address challenges in the sustainable synthesis of pharmaceuticals, commodity chemicals, fuels, feedstocks and fertilizers. However, the specialized experimental setups and domain knowledge for bioelectrocatalysis pose a significant barrier to adoption. This review introduces key concepts of bioelectrosynthetic systems. We provide a tutorial on the methods of biocatalyst utilization, the setup of bioelectrosynthetic cells, and the analytical methods for assessing bioelectrocatalysts. Key applications of bioelectrosynthesis in ammonia production and small‐molecule synthesis are outlined for both enzymatic and microbial systems. This review serves as a necessary introduction and resource for the non‐specialist interested in bioelectrosynthetic research.
... Examples of PCET reactions for several alcohols and MCFAs are shown in equations 3-7 below. [143] Acetic acid : ...
Bioelectrocatalytic synthesis is the conversion of electrical energy into value-added chemicals via a biocatalyst. Bioelectrosynthetic methods utilize the specificity and selectivity of biocatalytic enzymatic or microbial species to carry out chemical redox transformations while utilizing electricity as a stoichiometric redox equivalent. As a merging of biocatalysis and electrocatalysis, these methods directly address challenges in green and sustainable synthesis of pharmaceuticals, commodity chemicals, fuels, feedstocks and fertilizers. Despite the rising importance of bioelectrochemical transformations across these industries, there remains a high barrier for adoption due to the specialized experimental setups and domain knowledge for bioelectrocatalysis. This review aims to introduce the key concepts and design features of bioelectrosynthetic systems. A tutorial on the methods of biocatalyst utilization and the setup of bioelectrosynthetic cells is provided, as well as an overview of the analytical methods used for assessing bioelectrocatalysts. Key studies illustrating the vital applications of bioelectrosynthesis are outlined, such as ammonia production, small-molecule synthesis, and multi-carbon product formation. Finally, we address future directions for both microbial and enzymatic electrosynthetic methods. In summary, this review provides a critically necessary introduction to the field and a collection of resources for the non-specialist interested in pursuing a research program in bioelectrosynthesis.
... In MECs, biological waste transforms into hydrogen gas [3]. MES systems use anaerobic bacteria as biocatalysts to convert substrates such as carbon dioxide into valuable compounds [4]. Although recycling CO 2 into organic chemicals via MES has received increased attention [4,5], in the MES system, electrons are exclusively supplied by an external power source because CO 2 reduction at the cathode is coupled to water oxidation at the anode [3], so, high potentials or costly catalysts are required to obtain the oxygen evolution reaction (OER) [6]. ...
... MES systems use anaerobic bacteria as biocatalysts to convert substrates such as carbon dioxide into valuable compounds [4]. Although recycling CO 2 into organic chemicals via MES has received increased attention [4,5], in the MES system, electrons are exclusively supplied by an external power source because CO 2 reduction at the cathode is coupled to water oxidation at the anode [3], so, high potentials or costly catalysts are required to obtain the oxygen evolution reaction (OER) [6]. ...
... Then, the prepared anode was transferred to the anodic chamber of the MFC. To prepare the anolyte (phosphate buffer 0.1 M, pH = 7), 4.3 g of KH 2 PO 4 , 4.4 g of K 2 HPO 4 , 0.5 g of NaCl, 0.38 g of NH 4 Cl, and 0.0198 g of CaCl 2 .2H 2 O, 0.2 g of MgSO 4 .7 H 2 O, and 2 g of NaHCO 3 were weighed correctly and dissolved in 1000 ml of distilled water [34]. Also, 141.8 g KH 2 PO 4 and 0.44 g KH 2 HPO 4 were measured and diluted in 500 ml of distilled water to form the catholyte solution (phosphate buffer 0.1 M). ...
... The operating cell voltage is inversely correlated with energy efficiency and directly correlated with the electrical energy cost per unit of synthesized product at constant coulombic efficiency (Spurgeon and Kumar, 2018). Since electricity input is the major operational expense impeding the commercial viability of electrochemical or MES processes, energy efficiency estimation is a key process parameter that cannot be ignored (Christodoulou et al., 2017). In this study, the conductive catholyte decreased the ohmic resistance, and as a result, a high process energy efficiency of up to 46 % was achieved in organic acid and hydrogen products. ...
Using saline electrolytes in combination with halophilic CO2-fixing lithotrophic microbial catalysts has been envisioned as a promising strategy to develop an energy-efficient microbial electrosynthesis (MES) process for CO2 utilization. Here, an enriched marine CO2-fixing lithotrophic microbial community dominated by Vibrio and Clostridium spp. was tested for MES of organic acids from CO2. At an applied Ecathode of -1V (vs Ag/AgCl) with 3.5 % salinity (78 mScm-1), it produced 379 ± 53 mg/L (6.31 ± 0.89 mM) acetic acid and 187 ± 43 mg/L (4.05 ± 0.94 mM) formic acid at 2.1 ± 0.30 and 1.35 ± 0.31 mM day-1, respectively production rates. Most electrons were recovered in acetate (68.3 ± 3 %), formate (9.6 ± 1.2 %) besides hydrogen (11 ± 1.4 %) and biomass (8.9 ± 1.65 %). Notably, the bioproduction of organic acids occurred at a high energetic efficiency (EE) of ∼ 46 % and low Ecell of 2.3 V in saline conditions compared to the commonly used non-saline electrolytes (0.5-1 mScm-1) in the reported MES studies with CO2 (Ecell: >2.5 V and EE: <34 %).
... Thus, with current materials used in the construction of the cells, the cost of using BES for wastewater treatment is still significantly higher than activated sludge or anaerobic digestion (Rozendal et al., 2008). According to a study performed by Christodoulou et al. (2017), formic acid is the product that can be produced by means of a MES with the lowest production cost (0.49 £/kg), which is a competitive cost with respect to traditional production systems. ...
Bioelectrochemistry has gained importance in recent years for some of its applications on waste valorization, such as wastewater treatment and carbon dioxide conversion, among others. The aim of this review is to provide an updated overview of the applications of bioelectrochemical systems (BESs) for waste valorization in the industry, identifying current limitations and future perspectives of this technology. BESs are classified according to biorefinery concepts into three different categories: (i) waste to power, (ii) waste to fuel and (iii) waste to chemicals. The main issues related to the scalability of bioelectrochemical systems are discussed, such as electrode construction, the addition of redox mediators and the design parameters of the cells. Among the existing BESs, microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) stand out as the more advanced technologies in terms of implementation and R&D investment. However, there has been little transfer of such achievements to enzymatic electrochemical systems. It is necessary that enzymatic systems learn from the knowledge reached with MFC and MEC to accelerate their development to achieve competitiveness in the short term.
