ACETOGENS AND C1 BIOREFINERY
Acetogens are obligately anaerobic bacteria capable of synthesizing acetyl-CoA, cell carbon and energy from CO2 by the Wood-Ljungdahl pathway (WLP). Most acetogens can utilize a wide range of substrates from heterotrophic substrates (e.g., glucose and fructose) to lithotrophic C1 compounds (e.g., CO and methanol) as well as hydrogen, enabling their growth on various industrial waste gases, including those produced from steel manufacturing, oil refining, natural gas and coal. They are commonly referred to as "homoacetogens", since the majority of acetogens produce only acetate as a result of C1 gas and hydrogen utilization (Kim et al. Acetogens and acetogenesis for biological syngas valorization, Bioresour Technol, 2023, 129368).
C1 biorefinery refers to "biocatalytic reaction" using microorganisms which has an ability converting C1 gases (CO, CO2) and hydrogen (H2) to multi-carbon chemicals and products. The reaction is mainly conducted by microorganisms called "acetogens" due to their metabolic features on multi-carbon chemicals production ability. These microorganisms are generally recognized as "very hard to be genetically manipulated" because of that these organisms are strict anaerobic, physiologically thick cell wall possessed, less genetic toolbox studied and developed. There are a few cases of acetogens' metabolic engineering and successful studies reported. This strain development and use as biocatalyst are the issue of "upstream" of C1 biorefinery, and there are also midstream and downstream reactions and processes to study and develop.
Selected recent publications related to metabolic engineering of acetogens
Kang B et al (2023) Regulatory transcription factor (CooA)-driven carbon monoxide partial pressure sensing whole-cell biosensor. Heliyon, 9(6):e17391
Kim J-Y et al (2023) Acetogen and acetogenesis for biological syngas valorization. Bioresource Technology, 384:129368
Kang H et al (2021) Metabolism perturbation caused by the overexpression of carbon monoxide dehydrogenase/acetyl-CoA synthase gene complex accelerated gas to acetate conversion rate of Eubacterium limosum KIST612. Bioresource Technology, 125879
Kim J-Y et al (2021) Methanol supply speeds up synthesis gas fermentation by methylotrophic-acetogenic bacterium, Eubacterium limosum KIST612. Bioresource Technology, 321:124521
Kang H et al (2019) Gene-centric metagenome analysis reveals gene clusters for carbon monoxide conversion and validates isolation of a Clostridial acetogen for C2 chemical production. Biotechnology Journal, 14(6)
Selected recent publications related to process engineering for C1 refinery
Kim J-H et al (2023) Recycling of minerals with acetate separation in biological syngas fermentation with an electrodialysis system. Chemical Engineering Journal, 459:141555
Jang N et al (2020) Gas circulation rate and medium exchange ratio as influential factors affecting ethanol production in carbon monoxide fermentation using a packed-bed reactor. Sustainable Energy & Feuls, 4(4):1693-1973
Lee M et al (2020) A simultaneous gas feeding and cell-recycled reaction (SGCR) system to achieve biomass boosting and high acetate titer in microbial carbon monoxide fermentation. Bioresource Technology, 298:122549
Jang N et al (2020) Behavior of CO-water mass transfer coefficient in membrane sparger-integrated bubble column for synthesis gas fermentation. Bioresource Technology, 311:123594
Yasin M et al (2019) Bioreactors, gas delivery systems and supporting technologies for microbial synthesis gas conversion process. Bioresource Technology Reports, 7:100207
Jang N et al (2018) Bubble coalescence suppression driven carbon monoxide (CO)-water mass transfer increase by electrolyte addition in a hollow fiber membrane bioreactor (HFMBR) for microbial CO conversion to ethanol. Bioresource Technology, 263:375-384