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1. Electrohydrodimerization of biomass-derived furfural generates a jet fuel precursor

   https://doi.org/10.1039/d0gc01720e  

   Shang, Xiao ; Yang, Yang ; Sun, Yujie ( August 2020 , Green Chemistry)

   null (Ed.)

   Despite the increasing interest in upgrading biomass-derived molecules to value-added products, the electrochemical conversion of biomass platform chemicals to highly valuable biofuels, such as jet fuel, has not yet received wide attention. Herein, we report a catalyst-free electrochemical route for the production of a jet fuel precursor, hydrofuroin, from the electrohydrodimerization of furfural, which can be readily derived from lignocellulose and already has an industrial production of 300 000 tons per year. Detailed electrochemical studies using carbon and copper electrodes at various pH values enabled us to probe the reduction mechanism of furfural and obtain the kinetic details, such as the diffusion constant and electron transfer rate. Preparative electrolysis in a batch electrolyzer achieved a high yield of hydrofuroin (94%) with an excellent faradaic efficiency of 93%. Finally, a flow electrolyzer was employed to demonstrate the great promise of large-scale production of hydrofuroin from the electrohydrodimerization of furfural. 

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2. Electrosynthesis of amino acids from biomass-derived α-hydroxyl acids

   https://doi.org/10.1039/d2gc01779b  

   Yan, Kaili ; Huddleston, Morgan L. ; Gerdes, Brett A. ; Sun, Yujie ( July 2022 , Green Chemistry)

   Electrochemical conversion of biomass-derived intermediate compounds to high-value products has emerged as a promising approach in the field of biorefinery. Biomass upgrading allows for the production of chemicals from non-fossil-based carbon sources and capitalization on electricity as a green energy input. Amino acids, as products of biomass upgrading, have received relatively little attention. Pharmaceutical and food industries will benefit from an alternative strategy for the production of amino acids that does not rely on inefficient fermentation processes. The use of renewable biomass resources as starting materials makes this proposed strategy more desirable. Herein, we report an electrochemical approach for the selective oxidation of biomass-derived α-hydroxyl acids to α-keto acids, followed by electrochemical reductive amination to yield amino acids as the final products. Such a strategy takes advantage of both reactions at the anode and cathode and produces amino acids under ambient conditions with high energy efficiency. A flow electrolyzer was also successfully employed for the conversion of α-hydroxyl acids to amino acids, highlighting its great potential for large-scale application. 

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3. Photoelectrochemical approaches for the conversion of lignin at room temperature

   https://doi.org/10.1039/d2cc05491d  

   Li, Shuya ; Park, Seongsu ; Sherman, Benjamin D. ; Yoo, Chang Geun ; Leem, Gyu ( January 2023 , Chemical Communications)

   The selective cleavage of C–C/C–O linkages represents a key step toward achieving the chemical conversion of biomass to targeted value-added chemical products under ambient conditions. Using photoelectrosynthetic solar cells is a promising method to address the energy intensive depolymerization of lignin for the production of biofuels and valuable chemicals. This feature article gives an in-depth overview of recent progress using dye-sensitized photoelectrosynthetic solar cells (DSPECs) to initiate the cleavage of C–C/C–O bonds in lignin and related model compounds. This approach takes advantage of N -oxyl mediated catalysis in organic electrolytes and presents a promising direction for the sustainable production of chemicals currently derived from fossil fuels. 

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4. Hydrolysis of lignocellulose by anaerobic fungi produces free sugars and organic acids for two‐stage fine chemical production with Kluyveromyces marxianus

   https://doi.org/10.1002/btpr.3172  

   Hillman, Ethan T. ; Li, Mengwan ; Hooker, Casey A. ; Englaender, Jacob A. ; Wheeldon, Ian ; Solomon, Kevin V. ( May 2021 , Biotechnology Progress)

   Development of the bioeconomy is driven by our ability to access the energy‐rich carbon trapped in recalcitrant plant materials. Current strategies to release this carbon rely on expensive enzyme cocktails and physicochemical pretreatment, producing inhibitory compounds that hinder subsequent microbial bioproduction. Anaerobic fungi are an appealing solution as they hydrolyze crude, untreated biomass at ambient conditions into sugars that can be converted into value‐added products by partner organisms. However, some carbon is lost to anaerobic fungal fermentation products. To improve efficiency and recapture this lost carbon, we built a two‐stage bioprocessing system pairing the anaerobic fungusPiromyces indianaewith the yeastKluyveromyces marxianus, which grows on a wide range of sugars and fermentation products. In doing so we produce fine and commodity chemicals directly from untreated lignocellulose.P.indianaeefficiently hydrolyzed substrates such as corn stover and poplar to generate sugars, fermentation acids, and ethanol, whichK.marxianusconsumed while producing 2.4 g/L ethyl acetate. An engineered strain ofK.marxianuswas also able to produce 550 mg/L 2‐phenylethanol and 150 mg/L isoamyl alcohol fromP.indianaehydrolyzed lignocellulosic biomass. Despite the use of crude untreated plant material, production yields were comparable to optimized rich yeast media due to the use of all available carbon including organic acids, which formed up to 97% of free carbon in the fungal hydrolysate. This work demonstrates that anaerobic fungal pretreatment of lignocellulose can sustain the production of fine chemicals at high efficiency by partnering organisms with broad substrate versatility.

    

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5. A Perspective in Future Biomanufacturing: Challenges in Industrial Fermentation—Understanding and Controlling Microbial Lifespan and Aging

   https://doi.org/10.35534/sbe.2023.10019  

   Yang, Shang-Tian ; Wang, Geng ; Qin, Zhen ( December 2023 , Synthetic Biology and Engineering)

   Zeng, A ; Yang, ST (Ed.)

   Biomanufacturing with broad applications in various industries is projected to reach a market value of ~30 trillion USD by 2030, accounting for more than one third of the global manufacturing output. Future biomanufacturing of industrial products will use novel synthetic biology tools and advanced bioprocesses to convert abundant biomass and waste resources into value-added products with comparable or superior properties to replace current petroleum-based products, thus enabling circular bioeconomy with affordable energy, economic growth, and innovation in renewable energy and chemicals production. However, biomanufacturing faces many challenges in its development that requires fundamental research in synthetic biology and novel bioprocesses involving multidisciplinary teams and academic-industry partnerships. In particular, aging and lifespan of microbial cells have been largely overlooked in industrial fermentation. Only recently have microbiologists realized that many microorganisms including yeasts (e.g., Saccharomyces cerevisiae) and bacteria (e.g., Escherichia coli) have chronological and replicative life spans which dramatically impact cell viability and longevity. In this article, we will give our perspective on how synthetic biology may contribute to overcoming some challenges facing industrial biotechnology for fuels and chemicals production from renewable sources, highlighting the importance of understanding and regulating microorganism’s lifespan and aging. 

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