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Biology Articles » Bioengineering » Molecular and bioengineering strategies to improve alginate and polydydroxyalkanoate production by Azotobacter vinelandii » Figures

Figures
- Molecular and bioengineering strategies to improve alginate and polydydroxyalkanoate production by Azotobacter vinelandii

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Figure 1 Pathways for alginate and poly-β-hydroxybutyrate (PHB) biosynthesis and their metabolic relations in Azotobacter vinelandii. Dashed arrows indicate multi-enzyme pathways; the enzyme names and their abreviations are indicated in green and the corresponding genes are in red. PMI, phosphomannose isomerase; GMP, guanosine diphosphomannose pyrophosphorylase; PMM, phosphomannomutase; GMD, GDP-mannose dehydrogenase; MP, mannuronate polymerase; ME, mannuronate epimerase AlgG; MEs, mannuronate epimerases AlgE1 to 7.

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Figure 2 Organization of the A. vinelandii alginate and PHB biosynthetic genes. A model for the regulation of the synthesis of these polymers is presented. Green lines: positive regulation; red lines negative regulation; dashed lines indicate unknown intermediates or unknown mechanism of regulation. Promoters are indicated as colored rectangles.

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Figure 3 Alginate production (mucoidy; A, B) and PHB accumulation (opacity; C. D) of A. vinelandii wild type ATCC 9046 and mutant strains grown on plates containing sucrose as carbon source. The higher mucoid phenotype of strain AT6 (A) compared to ATCC9046 (B), shows the alginate overproducing phenotype of this strain unable to produce PHB. The absence of PHB granules in AT6 is shown in (F), as compared to ATCC9046 wild type (E). The increased opacity phenotype of the non-mucoid strain AT41 (C) when compared to ATCC 9046 (D), is due to the overproduction of PHB. The high content of PHB granules can be observed in the bright AT41 cells (G).

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Figure 4 Influence of the dissolved oxygen tension (DOT) on the molecular weight distribution of the alginate obtained with A. vinelandii SML2 strain. Dotted line 7 h, dashed line 13 h, solid line 21 h y 16 h (for 1% and 3–5 % of DOT respectively). Taken with permission from Trujillo-Roldán et al. [69].

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Figure 5 Effect of the scale of production on the mean molecular mass and polidispersity of the alginate obtained with the parental strain (ATCC9046) and various mutant strains. Circles: DM; Triangles: SML2.

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