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Bioreactor Controls-III01:22

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Strain improvement is a foundational strategy in industrial microbiology aimed at maximizing microbial productivity, particularly because natural isolates typically yield commercially valuable products in very low concentrations. Although optimizing the culture medium and environmental conditions can improve yields, these adjustments are inherently limited by the organism’s genetic potential. As a result, the focus shifts toward genetic modifications to enhance biosynthetic capacity. The...
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Characterizing Mediated Extracellular Electron Transfer in Lactic Acid Bacteria with a Three-Electrode, Two-Chamber Bioelectrochemical System
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Enabling unbalanced fermentations by using engineered electrode-interfaced bacteria.

Jeffrey M Flynn1, Daniel E Ross, Kristopher A Hunt

  • 1BioTechnology Institute, University of Minnesota Twin Cities, St. Paul, Minnesota, USA.

Mbio
|November 10, 2010
PubMed
Summary
This summary is machine-generated.

Engineered bacteria can now convert glycerol to ethanol using electrodes to balance cellular redox reactions. This novel biocatalysis platform overcomes metabolic constraints for efficient bioproduction.

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Light-Controlled Fermentations for Microbial Chemical and Protein Production
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Light-Controlled Fermentations for Microbial Chemical and Protein Production

Published on: March 22, 2022

Area of Science:

  • Microbial Engineering
  • Metabolic Engineering
  • Electromicrobiology

Background:

  • Cellular metabolism requires balanced oxidation-reduction (redox) reactions.
  • Fermentation and respiration face limitations in recycling electron carriers and electron acceptors.
  • Electrode-based electron acceptors offer a potential solution to overcome these metabolic constraints.

Purpose of the Study:

  • To engineer the bacterium Shewanella oneidensis for glycerol-to-ethanol conversion.
  • To demonstrate the use of electrode reduction as an external electron acceptor to balance biotransformations.
  • To establish a new platform for next-generation bioproduction strategies.

Main Methods:

  • Genetic engineering of Shewanella oneidensis by introducing glycerol and ethanol metabolic modules on a single plasmid.
  • Incorporation of genes (glpF, glpK, glpD, tpiA) for glycerol metabolism from Escherichia coli.
  • Introduction of genes (pdc, adh) for ethanol production from Zymomonas mobilis.
  • Disruption of the pta gene to eliminate acetate production and enhance ethanol yield.
  • Utilizing an electrode as an external electron acceptor to facilitate the biotransformation.

Main Results:

  • Successful stoichiometric conversion of glycerol to ethanol was achieved in engineered Shewanella oneidensis.
  • The biotransformation required the presence of an electrode to balance the reaction by accepting electrons.
  • Electrode-linked conversion rates were comparable to those observed in engineered E. coli.
  • Knocking out the pta gene shifted metabolic flux towards ethanol production, increasing product yields.

Conclusions:

  • Electrode-based electron acceptors can effectively balance microbial redox reactions, overcoming limitations of traditional fermentation and respiration.
  • Engineered Shewanella oneidensis provides a viable platform for glycerol-to-ethanol bioproduction, demonstrating a new approach to microbial biocatalysis.
  • Linking microbial biocatalysis to current production offers a versatile strategy for producing pure products and advancing bioproduction technologies.