Effect of phosphate and oxygen concentrations on alginate production and stoichiometry of metabolism of Azotobacter vinelandii under microaerobic conditions

Sabra, Wael; Zeng, An; Sabry, Soraya A.; Omar, Sanaa H.; Deckwer, Wolf‐Dieter

doi:10.1007/s002530051590

Cited by 40 publications

(34 citation statements)

References 25 publications

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“…On the other hand, q alg increased with increasing growth rate. The effect of pO 2 on the formation rate of alginate in continuous culture is in agreement with the results from pO 2 -controlled batch cultures with the same strain (38). Taken together, these results are useful for the optimization of the alginate production process.…”

supporting

confidence: 78%

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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

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181

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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supporting

confidence: 78%

“…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). A possible link between alginate formation and protection of nitrogenase in this organism has not been examined so far in the literature.…”

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

Self Cite

181

139

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show abstract

“…It is known that if M-blocks formed by consecutive mannuronic acid residues are dominant, soft and more flexible gels are formed; whereas if stretches of consecutive guluronic acid residues (G-blocks) are dominant, strong gels that are mostly resembled by an "egg-box structure" are formed (Grant et al 1973). Production of alginate from Azotobacter vinelandii has been widely studied by using shake flasks and fermenters (Clementi et al 1999;Diaz-Barrera et al 2010;Mejia et al 2010;Peña et al 1997;Savalgi and Savalgi 1992), and by differing the growth conditions, it is possible to reproducibly produce alginates with different content of G-blocks (Moral and Sanin 2012;Sabra et al 2000;Sabra et al 1999). A. vinelandii encode seven different secreted mannuronan C-5-epimerases (AlgE1-7) which introduce G residues in the polymer, and these may be used to increase the amount of G and G-blocks in vitro (Ertesvåg 2009).…”

Section: Introductionmentioning

confidence: 99%

Guluronic acid content as a factor affecting turbidity removal potential of alginate

Moral

Ertesvåg

Sanin

2016

Environ Sci Pollut Res

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Alginates are natural polymers composed of mannuronic and guluronic acid residues.They are currently extracted from brown algae, however, alginate can also be synthesized by some species of Azotobacter and Pseudomonas. Alginates with different proportion of mannuronic and guluronic acids are known to have different characteristics and form gels at different extents in the presence of calcium ions. The aim of this work was to investigate the usefulness of alginate as a non-toxic coagulant used in purification of drinking water. This study utilized alginates from Azotobacter vinelandii having different guluronic acid levels. These were obtained partly by changing the cultivation parameters, partly by epimerizing a purified alginate sample in vitro using the A. vinelandii mannuronan-C-5-epimerase AlgE1. The different alginates were then used for coagulation together with calcium. The results showed that turbidity removal capability was dependent on the content of guluronic acid residues. For the best performing samples the turbidity decreased from 10 NTU to 1 NTU by the use of only 2 mg/L of alginate and 1.5 mM of calcium chloride.

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“…Nestes estudos, busca-se também entender melhor as rotas metabólicas utilizadas pelos microrganismos para controlar a regulação, formação e composição do material biossintetizado e a otimização de seu processo de produção [5,20] . Pesquisas relacionadas ao estudo da estrutura do biopolímero indicam que o alginato sintetizado pelos gêneros Pseudomonas e Azotobacter é parcialmente acetilado e que os grupos acetil estão exclusivamente associados aos resíduos manurônicos.…”

Section: Produção De Alginato Por Bactériasunclassified

“…Neste contexto, o uso de bactérias proporciona um campo de pesquisa crescente para produzir e projetar biopolímeros com propriedades específicas [42] . Azotobacter vinelandii DSMZ 93-541b [20] 4,9 0,12 0,2…”

Section: Perspectivas Futuras Para Produção De Alginato Bacterianounclassified

Produção de alginato por microrganismos

2011

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Resumo: O alginato é um copolímero linear constituído de unidades de ácidos a-L-gulurônicos e b-D-manurônicos e é extensamente utilizado devido as suas propriedades espessantes, estabilizantes e gelificantes. Estas características fazem com que este biopolímero encontre aplicações na indústria de alimentos, na indústria têxtil e de papel, em cosméticos e na área farmacêutica e médica. Atualmente para este conjunto de aplicações sua principal fonte são algas marrons, entretanto, o alginato pode ser obtido a partir de biossíntese, utilizando-se microrganismos do gênero Pseudomonas e Azotobacter. A produção bacteriana de alginato apresenta-se como uma alternativa interessante e sua produção por microrganismos, além de possibilitar a produção de biopolímeros de alta qualidade com características específicas e pré-determinadas, irá diminuir o impacto ambiental nas regiões em que as algas marinhas das quais é extraído são coletadas. Nos últimos anos, vários estudos relacionados à produção de alginato por microrganismos foram realizados com o objetivo de avaliar sua produção e rota metabólica de biossíntese, para caracterizar o material produzido e para determinar as potencialidades de aplicação deste novo material. O rápido desenvolvimento de aplicações do alginato na área médica e farmacêutica, bem como a descoberta de propriedades imunológicas únicas deste material tem aumentado o interesse no desenvolvimento de processos para produzi-lo. Neste artigo são abordados aspectos relacionados à produção e as características do alginato bacteriano e também reportadas às potencialidades e aplicações inovadoras nas quais este material vem sendo utilizado. Palavras-chave: Azotobacter, Pseudomonas, alginato, alginato bacteriano, biopolímero. Alginate Production by MicroorganismsAbstract: Alginate is a linear copolymer consisting of units of a-L-guluronic and b-D-mannuronic acid which is widely used due to its thickening, stabilizing and gelling properties. These characteristics mean that it has many applications in the food, textile, paper, cosmetics and pharmaceutical industries, as well as in the medical area. Currently, the main source of alginate for such applications is brown algae; however, this biopolymer can be obtained through biosynthesis, using micro-organisms of the genera Pseudomonas and Azotobacter. The bacterial production of alginate represents an interesting alternative since, in addition to enabling the production of high quality polymers with predetermined and specific characteristics, it can reduce the environmental impact in areas from which the seaweed is collected. In recent years, several studies related to the production of alginate by microorganisms have been performed to evaluate the production process and metabolic pathway of biosynthesis, to characterize the material produced and to determine the potential applications of this new material. The rapid development of new applications of alginate in the medical and pharmaceutical areas, as well as the discovery of the unique immunological properties o...

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Effect of phosphate and oxygen concentrations on alginate production and stoichiometry of metabolism of Azotobacter vinelandii under microaerobic conditions

Cited by 40 publications

References 25 publications

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

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

Guluronic acid content as a factor affecting turbidity removal potential of alginate

Produção de alginato por microrganismos

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