The lack of a nitrogen source and/or the C/N ratio affects the molecular weight of alginate and its productivity in submerged cultures of Azotobacter vinelandii

2010 ◽  
Vol 60 (4) ◽  
pp. 661-668 ◽  
Author(s):  
Ana M. Zapata-Vélez ◽  
Mauricio A. Trujillo-Roldán
Keyword(s):  
Molecular Weight ◽  
Nitrogen Source ◽  
Azotobacter Vinelandii ◽  
Submerged Cultures

Partial repression of siderophore-mediated iron transport in Azotobacter vinelandii grown with mineral iron

1988 ◽  
Vol 34 (5) ◽  
pp. 675-679 ◽  
Author(s):  
William J. Page ◽  
Gregory A. Grant
Keyword(s):  
Molecular Weight ◽  
Outer Membrane ◽  
Iron Transport ◽  
Mineral Content ◽  
Azotobacter Vinelandii ◽  
Outer Membrane Proteins ◽  
Additional Component ◽  
Transport Activity ◽  
Fe Uptake ◽  
Mineral Concentrations

Azotobacter vinelandii grown in iron-limited medium containing increased amounts of the minerals olivine or glauconite produced decreased amounts of siderophores and iron-repressible outer membrane proteins. These minerals caused a relatively rapid repression of the pyoverdin-type siderophore, azotobactin, and a slower repression of the catechol siderophores, azotochelin and aminochelin. A 77 000 molecular weight outer membrane protein also was repressed with increased mineral content of the medium, but coordinate repression with any one siderophore was not evident. Cells grown with increased mineral concentrations progressively lost siderophore-mediated iron-transport activity. This loss in activity had the greatest effect on azotobactin-mediated 55Fe uptake, but catechol siderophore mediated 55Fe uptake also was depressed. These results suggested that an additional component was required for maximal iron-transport activity promoted by all the siderophores of A. vinelandii.

Effect of nitrogen source on carbon metabolism by Azotobacter vinelandii OP grown in chemostat and batch culture

1975 ◽  
Vol 21 (6) ◽  
pp. 738-741 ◽  
Author(s):  
W. G. W. Kurz ◽  
T. A. LaRue
Keyword(s):  
Nitrogen Source ◽  
Batch Culture ◽  
Carbon Metabolism ◽  
Azotobacter Vinelandii ◽  
Nitrogen Fixing ◽  
Malic Dehydrogenase ◽  
Specific Activities

Azotobacter vinelandii growing under nitrogen-fixing conditions has higher specific activities of isocitric and malic dehydrogenase than do cells growing on nitrate or ammonia. Results show that the source of nitrogen has an effect on carbon metabolism.

The URE2 gene product of Saccharomyces cerevisiae plays an important role in the cellular response to the nitrogen source and has homology to glutathione s-transferases

1991 ◽  
Vol 11 (2) ◽  
pp. 822-832 ◽  
Author(s):  
P W Coschigano ◽  
B Magasanik
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Molecular Weight ◽  
Glutamine Synthetase ◽  
Nitrogen Source ◽  
Gene Product ◽  
Cellular Response ◽  
Transcriptional Level ◽  
Structural Genes ◽  
Glutathione S Transferases

The URE2 gene of Saccharomyces cerevisiae has been cloned and sequenced. It encodes a predicted polypeptide of 354 amino acids with a molecular weight of 40,226. Deletion of the first 63 amino acids does not have any effect on the function of the protein. Studies with disruption alleles of the URE2 and GLN3 genes showed that both genes regulate GLN1 and GDH2, the structural genes for glutamine synthetase and NAD-linked glutamate dehydrogenase, respectively, at the transcriptional level, but expression of the regulatory genes does not appear to be regulated. Active URE2 gene product was required for the inactivation of glutamine synthetase upon addition of glutamine to cells growing with glutamate as the source of nitrogen. The predicted URE2 gene product has homology to glutathione S-transferases. The gene has been mapped to chromosome XIV, 5.9 map units from petX and 3.4 map units from kex2.

Manipulating the molecular weight of alginate produced by Azotobacter vinelandii in continuous cultures

2010 ◽  
Vol 101 (23) ◽  
pp. 9405-9408 ◽  
Author(s):  
Alvaro Díaz-Barrera ◽  
Paulina Silva ◽  
Julio Berrios ◽  
Fernando Acevedo
Keyword(s):  
Molecular Weight ◽  
Azotobacter Vinelandii ◽  
Continuous Cultures

scholarly journals Mechanistic basis for understanding the dual activities of the bifunctional Azotobacter vinelandii mannuronan C-5 epimerase and alginate lyase AlgE7

2021 ◽  
Author(s):  
Margrethe Gaardløs ◽  
Tonje Marita Bjerkan Heggeset ◽  
Anne Tøndervik ◽  
David Tezé ◽  
Birte Svensson ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Functional Properties ◽  
Catalytic Mechanism ◽  
Azotobacter Vinelandii ◽  
Brown Seaweed ◽  
Alginate Lyase ◽  
High Sequence Identity ◽  
Monomer Composition ◽  
Lyase Activity ◽  
Mechanistic Basis

The structure and functional properties of alginates are dictated by the monomer composition and molecular weight distribution. Mannuronan C-5 epimerases determine the monomer composition by catalysing the epimerization of β- d -mannuronic acid residues (M) into α- l -guluronic acid residues (G). The molecular weight is affected by alginate lyases, which catalyse a β-elimination mechanism that cleaves alginate chains. The reaction mechanisms for the epimerization and lyase reactions are similar and some enzymes can perform both reactions. These dualistic enzymes share high sequence identity with mannuronan C-5 epimerases without lyase activity. The mechanism behind their activity and the amino acid residues responsible for it are still unknown. We investigate mechanistic determinants involved in the bifunctional epimerase and lyase activity of AlgE7 from Azotobacter vinelandii . Based on sequence analyses, a range of AlgE7 variants were constructed and subjected to activity assays and product characterization by NMR. Our results show that calcium promotes lyase activity whereas NaCl reduces the lyase activity of AlgE7. By using defined poly-M and poly-MG substrates, the preferred cleavage sites of AlgE7 were found to be M|XM and G|XM, where X can be either M or G. From the study of AlgE7 mutants, R148 was identified as an important residue for the lyase activity, and the point mutant R148G resulted in an enzyme with only epimerase activity. Based on the results obtained in the present study we suggest a unified catalytic reaction mechanism for both epimerase and lyase activity where H154 functions as the catalytic base and Y149 as the catalytic acid. Importance Post-harvest valorisation and upgrading of algal constituents is a promising strategy in the development of a sustainable bioeconomy based on algal biomass. In this respect, alginate epimerases and lyases are valuable enzymes for tailoring of the functional properties of alginate, a polysaccharide extracted from brown seaweed with numerous applications in food, medicine, and material industries. By providing a better understanding of the catalytic mechanism and of how the two enzyme actions can be altered by changes in reaction conditions, this study opens for further applications of bacterial epimerases and lyases in enzymatic tailoring of alginate polymers.

scholarly journals The production, molecular weight and viscosifying power of alginate produced by Azotobacter vinelandii is affected by the carbon source in submerged cultures

DYNA ◽  
2015 ◽  
Vol 82 (194) ◽  
pp. 21-26 ◽  
Author(s):  
Mauricio A. Trujillo-Roldán ◽  
John Fredy Monsalve-Gil ◽  
Angélica Maria Cuesta-Álvarez ◽  
Norma A. Valdez-Cruz
Keyword(s):  
Molecular Weight ◽  
Carbon Source ◽  
Biomass Concentration ◽  
Sugarcane Juice ◽  
Added Value ◽  
Specific Productivity ◽  
Molecular Characteristics ◽  
Submerged Cultures ◽  
Alginate Production ◽  
The Impact

Alginate is a linear polymer composed of <span style="font-family: symbol;">b</span>-1,4 linked mannuronic acid and its epimer, <span style="font-family: symbol;">a</span>-L-guluronic acid, and frequently extracted from marine algae, as from bacteria such as Azotobacter and Pseudomonas. Here, we show the impact of conventional and unconventional carbon sources on A. vinelandii growth, alginate production, its mean molecular weight (MMW) and its viscosifying power. Starting with 20 g/L of sugars, the highest biomass concentration was obtained using deproteinized and hydrolyzed whey (6.67±0.72 g/L), and sugarcane juice (6.68±0.45 g/L). However, the maximum alginate production was achieved using sucrose (5.11±0.37 g/L), as well the highest alginate yield and specific productivity. Otherwise, the higher alginate MMW was obtained using sugarcane juice (1203±120 kDa), and the higher viscosifying power was obtained using deproteinized/ hydrolyzed whey (23.8±2.6 cps L/galg). This information suggests that it is possible to manipulate the productivity and molecular characteristics of alginates, as a function of the carbon source used. All this, together with the knowledge of the effects of environmental conditions will allow for high yields of high added value biopolymers.

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