Engineering topics
Publications and source records attributed to Lipscomb, Gina L..
Previously, the highest temperature for biological ethanol production was 85°C. Here, we have engineered ethanol production at 95°C by the hyperthermophilic archaeon Pyrococcus furiosus .
The bio-based production of organic chemicals provides a sustainable alternative to fossil-based production in the face of today’s climate challenges. In this work, we present a genome-scale metabolic reconstruction of Pyrococcus furiosus , a well-established platform organism that has been engineered to produce a variety of chemicals and fuels.
Microbial deconstruction of lignocellulose for the production of biofuels and chemicals requires the hydrolysis of heterogeneous hemicelluloses to access the microcrystalline cellulose portion. This work extends previous in vivo and in vitro efforts to characterize hemicellulose utilization by integrating genomic reconstruction, transcriptomic data, operon structures, and biochemical characteristics of key enzymes to understand the deployment and functionality of hemicellulases by the extreme thermophile Caldicellulosiruptor bescii .
Significance Electron bifurcation is a recently recognized mechanism of biological energy conservation that is widespread in anaerobic microorganisms and provides low-potential, high-energy electrons to drive otherwise nonspontaneous metabolic reactions. Here we describe the structure of a membrane-associated bifurcating enzyme from an aerobic microorganism. Termed Fix/EtfABCX, this enzyme is used by some nitrogen-fixing microbes to drive the low-potential reduction of nitrogen gas to ammonia. Fix/EtfABCX is a superdimer and a catalytic mechanism is proposed involving six flavins, two of which bifurcate, four iron-sulfur clusters, and two menaquinones. Fix/EtfABCX shares structural similarity with mammalian quinone oxidoreductase involved in mitochondrial fatty acid oxidation, suggesting an unexpected evolutionary link between bifurcating and nonbifurcating systems.
Abstract Caldicellulosiruptor bescii is the most thermophilic cellulolytic organism yet identified (Topt 78 °C). It grows on untreated plant biomass and has an established genetic system thereby making it a promising microbial platform for lignocellulose conversion to bio-products. Here, we investigated the ability of engineered C. bescii to generate alcohols from carboxylic acids. Expression of aldehyde ferredoxin oxidoreductase (aor from Pyrococcus furiosus) and alcohol dehydrogenase (adhA from Thermoanaerobacter sp. X514) enabled C. bescii to generate ethanol from crystalline cellulose and from biomass by reducing the acetate produced by fermentation. Deletion of lactate dehydrogenase in a strain expressing the AOR–Adh pathway increased ethanol production. Engineered strains also converted exogenously supplied organic acids (isobutyrate and n-caproate) to the corresponding alcohol (isobutanol and hexanol) using both crystalline cellulose and switchgrass as sources of reductant for alcohol production. This is the first instance of an acid to alcohol conversion pathway in a cellulolytic microbe.