Optimal conditions for alginate production by Azotobacter vinelandii

Clementi, Francesca; Fantozzi, Paolo; Mancini, Francesca; Moresi, Mauro

doi:10.1016/0141-0229(95)00007-0

Cited by 60 publications

(50 citation statements)

References 10 publications

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“…Alginate is an extracellular polysaccharide produced by a variety of gram-negative bacteria, including Azotobacter vinelandii, Pseudomonas fluorescens, and P. aeruginosa (32). Structurally, alginate is a linear glycoronan composed of (1 3 4)-linked residues of ␤-D-mannuronic acid and its C-(5)-epimer ␣-L-guluronic acid, and physically it has the property of forming viscous solutions and gels (8). Learn et al (24) have investigated hypochlorite scavenging by P. aeruginosa alginate, and apparently the uronic acid core and the O-acetyl groups of pseudomonal alginate have the ability to scavenge hypochlorite.…”

Section: Discussionmentioning

confidence: 99%

Curvularia Haloperoxidase: Antimicrobial Activity and Potential Application as a Surface Disinfectant

Hansen

Albertsen

Schäfer

et al. 2003

Appl Environ Microbiol

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A presumed antimicrobial enzyme system, the Curvularia haloperoxidase system, was examined with the aim of evaluating its potential as a sanitizing agent. In the presence of hydrogen peroxide, Curvularia haloperoxidase facilitates the oxidation of halides, such as chloride, bromide, and iodide, to antimicrobial compounds. The Curvularia haloperoxidase system caused several-log-unit reductions in counts of bacteria (Pseudomonas spp., Escherichia coli, Serratia marcescens, Aeromonas salmonicida, Shewanella putrefaciens, Staphylococcus epidermidis, and Listeria monocytogenes), yeasts (Candida sp. and Rhodotorula sp.), and filamentous fungi (Aspergillus niger, Aspergillus tubigensis, Aspergillus versicolor, Fusarium oxysporum, Penicillium chrysogenum, and Penicillium paxilli) cultured in suspension. Also, bacteria adhering to the surfaces of contact lenses were killed. The numbers of S. marcescens and S. epidermidis cells adhering to contact lenses were reduced from 4.0 and 4.9 log CFU to 1.2 and 2.7 log CFU, respectively, after treatment with the Curvularia haloperoxidase system. The killing effect of the Curvularia haloperoxidase system was rapid, and 10 6 CFU of E. coli cells/ml were eliminated within 10 min of treatment. Furthermore, the antimicrobial effect was short lived, causing no antibacterial effect against E. coli 10 min after the system was mixed. Bovine serum albumin (1%) and alginate (1%) inhibited the antimicrobial activity of the Curvularia haloperoxidase system, whereas glucose and Tween 20 did not affect its activity. In conclusion, the Curvularia haloperoxidase system is an effective sanitizing system and has the potential for a vast range of applications, for instance, for disinfection of contact lenses or medical devices.

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Section: Discussionmentioning

confidence: 99%

Curvularia Haloperoxidase: Antimicrobial Activity and Potential Application as a Surface Disinfectant

Hansen

Albertsen

Schäfer

et al. 2003

Appl Environ Microbiol

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“…Under favorable growth conditions, the coat swells and the cyst germinates, divides, and releases a vegetative cell. However, the formation of a cyst in A. vinelandii does not explain the formation of alginate by vegetative cells under conditions not favoring encystment (7,41).…”

mentioning

confidence: 99%

“…vinelandii is known to produce alginate under aerobic conditions (1,2,7,8,16,19). The formation of alginate is strongly affected by oxygen tension, especially in nitrogen-free medium and with limited phosphate (17,38).…”

mentioning

confidence: 99%

Effect of Oxygen on Formation and Structure of Azotobacter vinelandii Alginate and Its Role in Protecting Nitrogenase

Sabra

Zeng

Lünsdorf

et al. 2000

Appl Environ Microbiol

183

139

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The activity of nitrogenase in the nitrogen-fixing bacterium Azotobacter vinelandii grown diazotrophically under aerobic conditions is generally considered to be protected against O 2 by a high respiration rate. In this work, we have shown that a high rate of respiration is not the prevailing mechanism for nitrogenase protection in A. vinelandii grown in phosphate-limited nitrogen-free chemostat culture. Instead, the formation of alginate appeared to play a decisive role in protecting the nitrogenase that is required for cell growth in this culture. Depending on the O 2 tension and cell growth rate, the formation rate and composition of alginate released into the culture broth varied significantly. Furthermore, transmission electron microscopic analysis of cell morphology and the cell surface revealed the existence of an alginate capsule on the surface of A. vinelandii. The composition, thickness, and compactness of this alginate capsule also varied significantly. In general, increasing O 2 tension led to the formation of alginate with a higher molecular weight and a greater L-guluronic acid content. The alginate capsule was accordingly thicker and more compact. In addition, the formation of the alginate capsule was found to be strongly affected by the shear rate in a bioreactor. Based on these experimental results, it is suggested that the production of alginate, especially the formation of an alginate capsule on the cell surface, forms an effective barrier for O 2 transfer into the cell. It is obviously the quality, not the quantity, of alginate that is decisive for the protection of nitrogenase.

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“…The ability of bacteria to produce exopolysaccharide was determined by increase of broth apparent viscosity or presence of gel or pellicle in fermentation broth (Schwartz and Bodie, 1985). 428 and pharmaceutical fields (Clementi, 1997). All alginates produced by bacteria were, in all cases, reported to be rich in mannuronic acid (Dekwer and Hempel, 1999).…”

Section: Exopolysaccharide Productionmentioning

confidence: 99%

Alginate biopolymer production by Azotobacter chroococcum from whey degradation

Khanafari

Sepahei

2007

Int. J. Environ. Sci. Technol.

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ABSTRACT:The potential of three Azotobacter chroococcum strains for whey degradation and alginate production were investigated. After dilution, samples were spread plated on isolation agar and Manitol agar and incubated at 30 °C for 24 h. Microorganisms were screened for their ability to whey degradation and alginate production based on colony morphology, negative and capsule staining, ability to decrease the apparent turbidity of the fermentation broths in batch and semi continuous culture by spectrophotometer assay at 400 nanometer and tensiometer assay. Of the three strains tested for whey degradation, only Azotobacter chroococcum 1723 produced significant apparent growth on whey broth and could decrease about 70 % of turbidity in fermentation broth during 6 days in batch culture. Colonies of this strain was characteristically yellow, large, moucoid and slimy on whey agar than Manitol agar after 24 h at 30 °C. Transmission electron microscopy assay and Carbazole reagent were used to recognize the alginate biopolymer. After optimizing environmental factors such as pH, salt concentration and temperature, this strain was able to produce exopolysaccharide greater than 5 mg/mL. Optimum results were obtained when using whey broth as a fermentation medium without extra salt, temperature at 35 °C and pH 7. Increasing inorganic and organic nitrogen sources (yeast extract and NH 4 NO 3 ) reduced whey degradation at least 30%. Transmission electron microscopy assay showed a net-structured polysaccharide capsule around the cells. Semi-continuous culture results demonstrated that, alginate production as well as whey degradation was decreased (1 mg/mL and 30 %).

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Optimal conditions for alginate production by Azotobacter vinelandii

Cited by 60 publications

References 10 publications

Curvularia Haloperoxidase: Antimicrobial Activity and Potential Application as a Surface Disinfectant

Curvularia Haloperoxidase: Antimicrobial Activity and Potential Application as a Surface Disinfectant

Effect of Oxygen on Formation and Structure of Azotobacter vinelandii Alginate and Its Role in Protecting Nitrogenase

Alginate biopolymer production by Azotobacter chroococcum from whey degradation

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