Browsing by Author "Antoniewicz,Maciek R."
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Item CO2 fixation by anaerobic non-photosynthetic mixotrophy for improved carbon conversion(Nature Publishing Group, 9/30/16) Jones,Shawn W.; Fast,Alan G.; Carlson,Ellinor D.; Wiedel,Carrissa A.; Au,Jennifer; Antoniewicz,Maciek R.; Papoutsakis,Eleftherios T.; Tracy,Bryan P.; Shawn W. Jones, Alan G. Fast, Ellinor D. Carlson, Carrissa A. Wiedel, Jennifer Au, Maciek R. Antoniewicz, Eleftherios T. Papoutsakis & Bryan P. Tracy; Antoniewicz, Maciej Robert; Papoutsakis, EleftheriosMaximizing the conversion of biogenic carbon feedstocks into chemicals and fuels is essential for fermentation processes as feedstock costs and processing is commonly the greatest operating expense. Unfortunately, for most fermentations, over one-third of sugar carbon is lost to CO2 due to the decarboxylation of pyruvate to acetyl-CoA and limitations in the reducing power of the bio-feedstock. Here we show that anaerobic, non-photosynthetic mixotrophy, defined as the concurrent utilization of organic (for example, sugars) and inorganic (for example, CO2) substrates in a single organism, can overcome these constraints to increase product yields and reduce overall CO2 emissions. As a proof-of-concept, Clostridium ljungdahlii was engineered to produce acetone and achieved a mass yield 138% of the previous theoretical maximum using a high cell density continuous fermentation process. In addition, when enough reductant (that is, H-2) is provided, the fermentation emits no CO2. Finally, we show that mixotrophy is a general trait among acetogens.Item Evolution of E. coli on [U-C-13] Glucose Reveals a Negligible Isotopic Influence on Metabolism and Physiology(Public Library Science, 3/10/16) Sandberg,Troy E.; Long,Christopher P.; Gonzalez,Jacqueline E.; Feist,Adam M.; Antoniewicz,Maciek R.; Palsson,Bernhard O.; Troy E. Sandberg, Christopher P. Long, Jacqueline E. Gonzalez, Adam M. Feist, Maciek R. Antoniewicz, Bernhard O. Palsson; Antoniewicz, Maciej RobertC-13-Metabolic flux analysis (C-13-MFA) traditionally assumes that kinetic isotope effects from isotopically labeled compounds do not appreciably alter cellular growth or metabolism, despite indications that some biochemical reactions can be non-negligibly impacted. Here, populations of Escherichia coli were adaptively evolved for similar to 1000 generations on uniformly labeled C-13-glucose, a commonly used isotope for C-13-MFA. Phenotypic characterization of these evolved strains revealed similar to 40% increases in growth rate, with no significant difference in fitness when grown on either labeled (C-13) or unlabeled (C-12) glucose. The evolved strains displayed decreased biomass yields, increased glucose and oxygen uptake, and increased acetate production, mimicking what is observed after adaptive evolution on unlabeled glucose. Furthermore, full genome re-sequencing revealed that the key genetic changes underlying these phenotypic alterations were essentially the same as those acquired during adaptive evolution on unlabeled glucose. Additionally, glucose competition experiments demonstrated that the wild-type exhibits no isotopic preference for unlabeled glucose, and the evolved strains have no preference for labeled glucose. Overall, the results of this study indicate that there are no significant differences between C-12 and C-13-glucose as a carbon source for E. coli growth.