Limits...
Production of L-carnitine by secondary metabolism of bacteria.

Bernal V, Sevilla A, Cánovas M, Iborra JL - Microb. Cell Fact. (2007)

Bottom Line: The use of different cell environments, such as growing, resting, permeabilized, dried, osmotically stressed, freely suspended and immobilized cells, to maintain enzymes sufficiently active for L-carnitine production is discussed in the text.Moreover, the combined application of both bioprocess and metabolic engineering has allowed a deeper understanding of the main factors controlling the production process, such as energy depletion and the alteration of the acetyl-CoA/CoA ratio which are coupled to the end of the biotransformation.Furthermore, the profiles of key central metabolic activities such as the TCA cycle, the glyoxylate shunt and the acetate metabolism are seen to be closely interrelated and affect the biotransformation efficiency.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry and Molecular Biology B and Immunology, Campus of Espinardo, University of Murcia, E-30100, Spain. jliborra@um.es.

ABSTRACT
The increasing commercial demand for L-carnitine has led to a multiplication of efforts to improve its production with bacteria. The use of different cell environments, such as growing, resting, permeabilized, dried, osmotically stressed, freely suspended and immobilized cells, to maintain enzymes sufficiently active for L-carnitine production is discussed in the text. The different cell states of enterobacteria, such as Escherichia coli and Proteus sp., which can be used to produce L-carnitine from crotonobetaine or D-carnitine as substrate, are analyzed. Moreover, the combined application of both bioprocess and metabolic engineering has allowed a deeper understanding of the main factors controlling the production process, such as energy depletion and the alteration of the acetyl-CoA/CoA ratio which are coupled to the end of the biotransformation. Furthermore, the profiles of key central metabolic activities such as the TCA cycle, the glyoxylate shunt and the acetate metabolism are seen to be closely interrelated and affect the biotransformation efficiency. Although genetically modified strains have been obtained, new strain improvement strategies are still needed, especially in Escherichia coli as a model organism for molecular biology studies. This review aims to summarize and update the state of the art in L-carnitine production using E. coli and Proteus sp, emphasizing the importance of proper reactor design and operation strategies, together with metabolic engineering aspects and the need for feed-back between wet and in silico work to optimize this biotransformation.

No MeSH data available.


Related in: MedlinePlus

L-carnitine metabolism in bacteria. A) Schematic representation of the main pathways for L(-)-carnitine metabolization in bacteria. Shaded and striped reactions correspond to the pathways observed in Enterobacteria and Acinetobacter strains, respectively. Reactions in the dashed box correspond to Pseudomonas strains. Enzymes or "systems" involved: 1, γ-butyrobetaine hydroxylase; 2, L-carnitine dehydrogenase; 3, L-carnitine dehydratase; 3a, "carnitinyl-CoA hydrolase"; 4, crotonobetaine reductase; 4a, "γ-butyrobetaine dehydrogenase"; 5, monooxygenase; 6, "carnitine racemase"; 7, D-carnitine dehydrogenase. Adapted from [4]. B) Complete anaerobic biotransformation pathway for trimethylammonium compounds in E. coli. Adapted from [30]. Abbreviations: Crot, crotonobetaine; γ-BB, γ-butyrobetaine, L-Car, L-carnitine; D-Car, D-carnitine; Gly, glycine; 3-dehydro-Car, 3-dehydrocarnitine; Me3N, trimethylamine; Mal, malate; Suc, succinate; CaiT, L-carnitine/γ-butyrobetaine/crotonobetaine protein transporter; CaiA, CaiB, crotonobetaine reduction reaction; CaiB, CoA transferase; CaiC, L-carnitine/γ-butyrobetaine/crotonobetaine CoA ligase; CaiD, enoyl-CoA hydratase or carnitine racemase activity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2131755&req=5

Figure 1: L-carnitine metabolism in bacteria. A) Schematic representation of the main pathways for L(-)-carnitine metabolization in bacteria. Shaded and striped reactions correspond to the pathways observed in Enterobacteria and Acinetobacter strains, respectively. Reactions in the dashed box correspond to Pseudomonas strains. Enzymes or "systems" involved: 1, γ-butyrobetaine hydroxylase; 2, L-carnitine dehydrogenase; 3, L-carnitine dehydratase; 3a, "carnitinyl-CoA hydrolase"; 4, crotonobetaine reductase; 4a, "γ-butyrobetaine dehydrogenase"; 5, monooxygenase; 6, "carnitine racemase"; 7, D-carnitine dehydrogenase. Adapted from [4]. B) Complete anaerobic biotransformation pathway for trimethylammonium compounds in E. coli. Adapted from [30]. Abbreviations: Crot, crotonobetaine; γ-BB, γ-butyrobetaine, L-Car, L-carnitine; D-Car, D-carnitine; Gly, glycine; 3-dehydro-Car, 3-dehydrocarnitine; Me3N, trimethylamine; Mal, malate; Suc, succinate; CaiT, L-carnitine/γ-butyrobetaine/crotonobetaine protein transporter; CaiA, CaiB, crotonobetaine reduction reaction; CaiB, CoA transferase; CaiC, L-carnitine/γ-butyrobetaine/crotonobetaine CoA ligase; CaiD, enoyl-CoA hydratase or carnitine racemase activity.

Mentions: In addition to the protective roles exhibited after accumulating betaines, some bacterial species are also able to metabolize these trimethylammonium compounds under different conditions [4]. Depending on the species and the cultivation conditions (carbon and nitrogen sources, aerobic or anaerobic conditions), different pathways are involved in L-carnitine catabolism. The initial enzymes of the various catabolic pathways are induced by L-carnitine, but also partly by other trimethylammonium compounds. Different genera are able to degrade L-carnitine under aerobic conditions, assimilating both carbon and nitrogen in the molecule backbone. Some Pseudomonas species (like Pseudomonas aeruginosa A7244 and Pseudomonas sp. AK1) are able to grow aerobically on L-carnitine as the sole source of carbon and nitrogen (Fig. 1A). In these species, L-carnitine degradation starts by oxidation of the hydroxyl group with the concomitant formation of 3-dehydrocarnitine by an L-carnitine dehydrogenase (EC 1.1.1.108) [10]. Pseudomonas sp. AK1 is also able to grow on γ-butyrobetaine, which is an intermediate in the degradation pathway [11]. This pathway has similarities with the biosynthetic pathway of L-carnitine in eukaryotes (Fig. 1A).


Production of L-carnitine by secondary metabolism of bacteria.

Bernal V, Sevilla A, Cánovas M, Iborra JL - Microb. Cell Fact. (2007)

L-carnitine metabolism in bacteria. A) Schematic representation of the main pathways for L(-)-carnitine metabolization in bacteria. Shaded and striped reactions correspond to the pathways observed in Enterobacteria and Acinetobacter strains, respectively. Reactions in the dashed box correspond to Pseudomonas strains. Enzymes or "systems" involved: 1, γ-butyrobetaine hydroxylase; 2, L-carnitine dehydrogenase; 3, L-carnitine dehydratase; 3a, "carnitinyl-CoA hydrolase"; 4, crotonobetaine reductase; 4a, "γ-butyrobetaine dehydrogenase"; 5, monooxygenase; 6, "carnitine racemase"; 7, D-carnitine dehydrogenase. Adapted from [4]. B) Complete anaerobic biotransformation pathway for trimethylammonium compounds in E. coli. Adapted from [30]. Abbreviations: Crot, crotonobetaine; γ-BB, γ-butyrobetaine, L-Car, L-carnitine; D-Car, D-carnitine; Gly, glycine; 3-dehydro-Car, 3-dehydrocarnitine; Me3N, trimethylamine; Mal, malate; Suc, succinate; CaiT, L-carnitine/γ-butyrobetaine/crotonobetaine protein transporter; CaiA, CaiB, crotonobetaine reduction reaction; CaiB, CoA transferase; CaiC, L-carnitine/γ-butyrobetaine/crotonobetaine CoA ligase; CaiD, enoyl-CoA hydratase or carnitine racemase activity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2131755&req=5

Figure 1: L-carnitine metabolism in bacteria. A) Schematic representation of the main pathways for L(-)-carnitine metabolization in bacteria. Shaded and striped reactions correspond to the pathways observed in Enterobacteria and Acinetobacter strains, respectively. Reactions in the dashed box correspond to Pseudomonas strains. Enzymes or "systems" involved: 1, γ-butyrobetaine hydroxylase; 2, L-carnitine dehydrogenase; 3, L-carnitine dehydratase; 3a, "carnitinyl-CoA hydrolase"; 4, crotonobetaine reductase; 4a, "γ-butyrobetaine dehydrogenase"; 5, monooxygenase; 6, "carnitine racemase"; 7, D-carnitine dehydrogenase. Adapted from [4]. B) Complete anaerobic biotransformation pathway for trimethylammonium compounds in E. coli. Adapted from [30]. Abbreviations: Crot, crotonobetaine; γ-BB, γ-butyrobetaine, L-Car, L-carnitine; D-Car, D-carnitine; Gly, glycine; 3-dehydro-Car, 3-dehydrocarnitine; Me3N, trimethylamine; Mal, malate; Suc, succinate; CaiT, L-carnitine/γ-butyrobetaine/crotonobetaine protein transporter; CaiA, CaiB, crotonobetaine reduction reaction; CaiB, CoA transferase; CaiC, L-carnitine/γ-butyrobetaine/crotonobetaine CoA ligase; CaiD, enoyl-CoA hydratase or carnitine racemase activity.
Mentions: In addition to the protective roles exhibited after accumulating betaines, some bacterial species are also able to metabolize these trimethylammonium compounds under different conditions [4]. Depending on the species and the cultivation conditions (carbon and nitrogen sources, aerobic or anaerobic conditions), different pathways are involved in L-carnitine catabolism. The initial enzymes of the various catabolic pathways are induced by L-carnitine, but also partly by other trimethylammonium compounds. Different genera are able to degrade L-carnitine under aerobic conditions, assimilating both carbon and nitrogen in the molecule backbone. Some Pseudomonas species (like Pseudomonas aeruginosa A7244 and Pseudomonas sp. AK1) are able to grow aerobically on L-carnitine as the sole source of carbon and nitrogen (Fig. 1A). In these species, L-carnitine degradation starts by oxidation of the hydroxyl group with the concomitant formation of 3-dehydrocarnitine by an L-carnitine dehydrogenase (EC 1.1.1.108) [10]. Pseudomonas sp. AK1 is also able to grow on γ-butyrobetaine, which is an intermediate in the degradation pathway [11]. This pathway has similarities with the biosynthetic pathway of L-carnitine in eukaryotes (Fig. 1A).

Bottom Line: The use of different cell environments, such as growing, resting, permeabilized, dried, osmotically stressed, freely suspended and immobilized cells, to maintain enzymes sufficiently active for L-carnitine production is discussed in the text.Moreover, the combined application of both bioprocess and metabolic engineering has allowed a deeper understanding of the main factors controlling the production process, such as energy depletion and the alteration of the acetyl-CoA/CoA ratio which are coupled to the end of the biotransformation.Furthermore, the profiles of key central metabolic activities such as the TCA cycle, the glyoxylate shunt and the acetate metabolism are seen to be closely interrelated and affect the biotransformation efficiency.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry and Molecular Biology B and Immunology, Campus of Espinardo, University of Murcia, E-30100, Spain. jliborra@um.es.

ABSTRACT
The increasing commercial demand for L-carnitine has led to a multiplication of efforts to improve its production with bacteria. The use of different cell environments, such as growing, resting, permeabilized, dried, osmotically stressed, freely suspended and immobilized cells, to maintain enzymes sufficiently active for L-carnitine production is discussed in the text. The different cell states of enterobacteria, such as Escherichia coli and Proteus sp., which can be used to produce L-carnitine from crotonobetaine or D-carnitine as substrate, are analyzed. Moreover, the combined application of both bioprocess and metabolic engineering has allowed a deeper understanding of the main factors controlling the production process, such as energy depletion and the alteration of the acetyl-CoA/CoA ratio which are coupled to the end of the biotransformation. Furthermore, the profiles of key central metabolic activities such as the TCA cycle, the glyoxylate shunt and the acetate metabolism are seen to be closely interrelated and affect the biotransformation efficiency. Although genetically modified strains have been obtained, new strain improvement strategies are still needed, especially in Escherichia coli as a model organism for molecular biology studies. This review aims to summarize and update the state of the art in L-carnitine production using E. coli and Proteus sp, emphasizing the importance of proper reactor design and operation strategies, together with metabolic engineering aspects and the need for feed-back between wet and in silico work to optimize this biotransformation.

No MeSH data available.


Related in: MedlinePlus