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Metabolic Engineering of Escherichia coli for Production of Mixed-Acid Fermentation End Products.

Förster AH, Gescher J - Front Bioeng Biotechnol (2014)

Bottom Line: Mixed-acid fermentation end products have numerous applications in biotechnology.This is probably the main driving force for the development of multiple strains that are supposed to produce individual end products with high yields.The process of engineering Escherichia coli strains for applied production of ethanol, lactate, succinate, or acetate was initiated several decades ago and is still ongoing.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Biosciences, Karlsruhe Institute of Technology , Karlsruhe , Germany.

ABSTRACT
Mixed-acid fermentation end products have numerous applications in biotechnology. This is probably the main driving force for the development of multiple strains that are supposed to produce individual end products with high yields. The process of engineering Escherichia coli strains for applied production of ethanol, lactate, succinate, or acetate was initiated several decades ago and is still ongoing. This review follows the path of strain development from the general characteristics of aerobic versus anaerobic metabolism over the regulatory machinery that enables the different metabolic routes. Thereafter, major improvements for broadening the substrate spectrum of E. coli toward cheap carbon sources like molasses or lignocellulose are highlighted before major routes of strain development for the production of ethanol, acetate, lactate, and succinate are presented.

No MeSH data available.


Related in: MedlinePlus

(A) Overview of the activation of the ArcAB two-component system [according to and modified from Liu et al. (2009)]. An accumulation of lactate, pyruvate or NADH triggers a phosphorylation cascade in ArcB that finally leads to the phosphorylation of ArcA. ArcA is depicted as a two-component protein containing the secondary receiver domain D2 and a helix-turn-helix domain (HTH). Oxidized quinone molecules negatively modulate the ArcB activity. (B) Schematic overview of FNR-regulator activation (according to and modified from Tolla and Savageau, 2010). Oxygen inactivates the active dimeric form of FNR that contains one 4Fe-4S-cluster per monomer (4Fe-4S FNR). Continuous production of new FNR molecules and reactivation of the inactive 2Fe-2S-form (2Fe-2S FNR) or the apoenzyme (apo FNR) leads to constant cycling of the three FNR-forms. The absence of oxygen triggers a rapid accumulation of the 4Fe-4S-form, which dimerizes and thereby becomes an active transcription factor.
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Figure 2: (A) Overview of the activation of the ArcAB two-component system [according to and modified from Liu et al. (2009)]. An accumulation of lactate, pyruvate or NADH triggers a phosphorylation cascade in ArcB that finally leads to the phosphorylation of ArcA. ArcA is depicted as a two-component protein containing the secondary receiver domain D2 and a helix-turn-helix domain (HTH). Oxidized quinone molecules negatively modulate the ArcB activity. (B) Schematic overview of FNR-regulator activation (according to and modified from Tolla and Savageau, 2010). Oxygen inactivates the active dimeric form of FNR that contains one 4Fe-4S-cluster per monomer (4Fe-4S FNR). Continuous production of new FNR molecules and reactivation of the inactive 2Fe-2S-form (2Fe-2S FNR) or the apoenzyme (apo FNR) leads to constant cycling of the three FNR-forms. The absence of oxygen triggers a rapid accumulation of the 4Fe-4S-form, which dimerizes and thereby becomes an active transcription factor.

Mentions: The two-component ArcAB system consists of the membrane-associated sensor kinase ArcB and the cytoplasmic response regulator ArcA (Iuchi and Lin, 1988; Iuchi et al., 1990) (Figure 2A). ArcB has three cytoplasmic domains (H1, D1, and H2) and two transmembrane segments (Iuchi et al., 1990; Kwon et al., 2000). Phosphorylation of H1 is inhibited by oxidized quinones within the cytoplasmic membrane (Georgellis et al., 2001; Bekker et al., 2010) and stimulated by lactate, acetate, and pyruvate (Georgellis et al., 1999). Phosphorylation of H1 leads via several steps to formation of phosphorylated ArcA (Georgellis et al., 1997). This modified protein regulates the expression of numerous genes involved in energy metabolism. It represses genes contributing to respiration and activates those involved in fermentation (Malpica et al., 2006; Liu et al., 2009). For example, the TCA cycle, almost exclusively contributing to anabolic reactions under anoxic conditions, is upregulated in an arcA deletion strain during nitrate respiration (Prohl et al., 1998; Toya et al., 2012). Therefore, Pettinari et al. (2008) suggested that arcA deletion strains could be promising candidates for the production of reduced bioproducts like polyhydroxyalkanoates. The rationale behind this assumption is that the upregulation of citric acid cycle enzymes under anoxic conditions could potentially lead to elevated concentrations of NADH or NADPH. Beside the above described functions, the ArcAB system is also involved in aerobic hydrogen peroxide resistance (Loui et al., 2009) and microaerobic redox regulation (Alexeeva et al., 2003).


Metabolic Engineering of Escherichia coli for Production of Mixed-Acid Fermentation End Products.

Förster AH, Gescher J - Front Bioeng Biotechnol (2014)

(A) Overview of the activation of the ArcAB two-component system [according to and modified from Liu et al. (2009)]. An accumulation of lactate, pyruvate or NADH triggers a phosphorylation cascade in ArcB that finally leads to the phosphorylation of ArcA. ArcA is depicted as a two-component protein containing the secondary receiver domain D2 and a helix-turn-helix domain (HTH). Oxidized quinone molecules negatively modulate the ArcB activity. (B) Schematic overview of FNR-regulator activation (according to and modified from Tolla and Savageau, 2010). Oxygen inactivates the active dimeric form of FNR that contains one 4Fe-4S-cluster per monomer (4Fe-4S FNR). Continuous production of new FNR molecules and reactivation of the inactive 2Fe-2S-form (2Fe-2S FNR) or the apoenzyme (apo FNR) leads to constant cycling of the three FNR-forms. The absence of oxygen triggers a rapid accumulation of the 4Fe-4S-form, which dimerizes and thereby becomes an active transcription factor.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4126452&req=5

Figure 2: (A) Overview of the activation of the ArcAB two-component system [according to and modified from Liu et al. (2009)]. An accumulation of lactate, pyruvate or NADH triggers a phosphorylation cascade in ArcB that finally leads to the phosphorylation of ArcA. ArcA is depicted as a two-component protein containing the secondary receiver domain D2 and a helix-turn-helix domain (HTH). Oxidized quinone molecules negatively modulate the ArcB activity. (B) Schematic overview of FNR-regulator activation (according to and modified from Tolla and Savageau, 2010). Oxygen inactivates the active dimeric form of FNR that contains one 4Fe-4S-cluster per monomer (4Fe-4S FNR). Continuous production of new FNR molecules and reactivation of the inactive 2Fe-2S-form (2Fe-2S FNR) or the apoenzyme (apo FNR) leads to constant cycling of the three FNR-forms. The absence of oxygen triggers a rapid accumulation of the 4Fe-4S-form, which dimerizes and thereby becomes an active transcription factor.
Mentions: The two-component ArcAB system consists of the membrane-associated sensor kinase ArcB and the cytoplasmic response regulator ArcA (Iuchi and Lin, 1988; Iuchi et al., 1990) (Figure 2A). ArcB has three cytoplasmic domains (H1, D1, and H2) and two transmembrane segments (Iuchi et al., 1990; Kwon et al., 2000). Phosphorylation of H1 is inhibited by oxidized quinones within the cytoplasmic membrane (Georgellis et al., 2001; Bekker et al., 2010) and stimulated by lactate, acetate, and pyruvate (Georgellis et al., 1999). Phosphorylation of H1 leads via several steps to formation of phosphorylated ArcA (Georgellis et al., 1997). This modified protein regulates the expression of numerous genes involved in energy metabolism. It represses genes contributing to respiration and activates those involved in fermentation (Malpica et al., 2006; Liu et al., 2009). For example, the TCA cycle, almost exclusively contributing to anabolic reactions under anoxic conditions, is upregulated in an arcA deletion strain during nitrate respiration (Prohl et al., 1998; Toya et al., 2012). Therefore, Pettinari et al. (2008) suggested that arcA deletion strains could be promising candidates for the production of reduced bioproducts like polyhydroxyalkanoates. The rationale behind this assumption is that the upregulation of citric acid cycle enzymes under anoxic conditions could potentially lead to elevated concentrations of NADH or NADPH. Beside the above described functions, the ArcAB system is also involved in aerobic hydrogen peroxide resistance (Loui et al., 2009) and microaerobic redox regulation (Alexeeva et al., 2003).

Bottom Line: Mixed-acid fermentation end products have numerous applications in biotechnology.This is probably the main driving force for the development of multiple strains that are supposed to produce individual end products with high yields.The process of engineering Escherichia coli strains for applied production of ethanol, lactate, succinate, or acetate was initiated several decades ago and is still ongoing.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Biosciences, Karlsruhe Institute of Technology , Karlsruhe , Germany.

ABSTRACT
Mixed-acid fermentation end products have numerous applications in biotechnology. This is probably the main driving force for the development of multiple strains that are supposed to produce individual end products with high yields. The process of engineering Escherichia coli strains for applied production of ethanol, lactate, succinate, or acetate was initiated several decades ago and is still ongoing. This review follows the path of strain development from the general characteristics of aerobic versus anaerobic metabolism over the regulatory machinery that enables the different metabolic routes. Thereafter, major improvements for broadening the substrate spectrum of E. coli toward cheap carbon sources like molasses or lignocellulose are highlighted before major routes of strain development for the production of ethanol, acetate, lactate, and succinate are presented.

No MeSH data available.


Related in: MedlinePlus