51
|
Steigedal M, Sletta H, Moreno S, Mærk M, Christensen BE, Bjerkan T, Ellingsen TE, Espìn G, Ertesvåg H, Valla S. The Azotobacter vinelandii AlgE mannuronan C-5-epimerase family is essential for the in vivo control of alginate monomer composition and for functional cyst formation. Environ Microbiol 2008; 10:1760-70. [DOI: 10.1111/j.1462-2920.2008.01597.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
52
|
Usov AI. Alginic acids and alginates: analytical methods used for their estimation and characterisation of composition and primary structure. RUSSIAN CHEMICAL REVIEWS 2007. [DOI: 10.1070/rc1999v068n11abeh000532] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
53
|
|
54
|
Kuo HH, Chan C, Burrows LL, Deber CM. Hydrophobic Interactions in Complexes of Antimicrobial Peptides with Bacterial Polysaccharides. Chem Biol Drug Des 2007; 69:405-12. [PMID: 17581234 DOI: 10.1111/j.1747-0285.2007.00518.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biofilms of Pseudomonas aeruginosa are responsible for chronic lung infections in cystic fibrosis patients, where they are characterized by overproduction of the exopolysaccharide alginate and are recalcitrant to treatment with conventional antibiotics. Cationic antimicrobial peptides (CAPs) are potential alternatives for the treatment of multi-drug-resistant P. aeruginosa. However, alginate in P. aeruginosa biofilms has been proposed to bind these peptides through hydrophobic interactions, consequently reducing their activity [Chan et al., J Biol Chem 2004; 279: 38749-38754]. Here we perform biophysical analyses of the interactions of alginate with a series of novel peptide antibiotics (alpha-CAPs) of prototypic sequence KK-AAAXAAAAAXAAWAAXAAA-KKKK (where X = Phe, Trp or Leu). The hydrophobic interaction interface in alginate was investigated by examining (i) the effects of polysaccharide composition with respect to D-mannuronate and L-guluronate content; (ii) glycan chain length; (iii) alpha-CAP Trp fluorescence; and (iv) 1-anilinonaphthalene-8-sulfonate fluorescence. The results show that, while M and G residues produce equivalent effects, hydrophobic interactions between alginate and alpha-CAPs require a minimal glycan chain length. Peptide interactions with alginate are deduced to be mediated by hydrophobic microdomains comprised of pyranosyl C-H groups that are inducible upon formation of alpha-CAP-alginate complexes due to charge neutralization between the two species.
Collapse
Affiliation(s)
- Hsin H Kuo
- Division of Molecular Structure & Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada M5G 1X8
| | | | | | | |
Collapse
|
55
|
Crognale S, Bruno M, Fidaleo M, Moresi M, Petruccioli M. Production of ?-glucan and related glucan-hydrolases by Botryosphaeria rhodina. J Appl Microbiol 2007; 102:860-71. [PMID: 17309637 DOI: 10.1111/j.1365-2672.2006.03116.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS Characterization of beta-glucan production from Botryosphaeria rhodina DABAC-P82 by detecting simultaneously glucan-hydrolytic enzymes and their localization, culture medium rheology and oxygen transfer. METHODS AND RESULTS Mycelium growth, beta-glucan production, substrate consumption and glucan-hydrolytic enzymes were monitored both in shaken flasks and in a 3-l stirred-tank bioreactor. Glucan production (19.7 and 15.2 g l(-1), in flask and bioreactor, respectively) was accompanied by extra-cellular and cell-bound beta-glucanase and beta-glucosidase activities. In the bioreactor scale, in the time interval of 0-78 h the apparent viscosity of the culture broth exhibited a general increase; thereafter, it began to reduce, probably because of the above glucan-hydrolytic activities. Moreover, the culture media collected after 45 h behaved as solid-like materials at shear rates smaller than 0.001 s(-1), as pseudo-plastic liquids in the middle shear rate range and as Newtonian ones at shear rates greater than 1000 s(-1). CONCLUSION The greatest beta-glucan accumulation in the bioreactor was found to be associated with nitrogen and dissolved oxygen concentrations smaller than 0.15 g l(-1) and 25%, respectively, and with the peak points of the glucan-degrading enzymes. SIGNIFICANCE AND IMPACT OF THE STUDY A careful analysis of the critical factors (such as, culture broth rheology, oxygen mass transfer and glucan-hydrolytic enzymes) limiting the beta-glucan production by B. rhodina is a prerequisite to maximize beta-glucan yield and production, as well as to define the process flow sheet capable of maximizing biopolymer recovery, solvent re-utilization and glucose consumption.
Collapse
Affiliation(s)
- S Crognale
- Dipartimento di Agrobiologia ed Agrochimica, University of Tuscia, Viterbo, Italy
| | | | | | | | | |
Collapse
|
56
|
Galindo E, Peña C, Núñez C, Segura D, Espín G. Molecular and bioengineering strategies to improve alginate and polydydroxyalkanoate production by Azotobacter vinelandii. Microb Cell Fact 2007; 6:7. [PMID: 17306024 PMCID: PMC1805506 DOI: 10.1186/1475-2859-6-7] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2006] [Accepted: 02/16/2007] [Indexed: 12/01/2022] Open
Abstract
Several aspects of alginate and PHB synthesis in Azotobacter vinelandii at a molecular level have been elucidated in articles published during the last ten years. It is now clear that alginate and PHB synthesis are under a very complex genetic control. Genetic modification of A. vinelandii has produced a number of very interesting mutants which have particular traits for alginate production. One of these mutants has been shown to produce the alginate with the highest mean molecular mass so far reported. Recent work has also shed light on the factors determining molecular mass distribution; the most important of these being identified as; dissolved oxygen tension and specific growth rate. The use of specific mutants has been very useful for the correct analysis and interpretation of the factors affecting polymerization. Recent scale-up/down work on alginate production has shown that oxygen limitation is crucial for producing alginate of high molecular mass, a condition which is optimized in shake flasks and which can now be reproduced in stirred fermenters. It is clear that the phenotypes of mutants grown on plates are not necessarily reproducible when the strains are tested in lab or bench scale fermenters. In the case of PHB, A. vinelandii has shown itself able to produce relatively large amounts of this polymer of high molecular weight on cheap substrates, even allowing for simple extraction processes. The development of fermentation strategies has also shown promising results in terms of improving productivity. The understanding of the regulatory mechanisms involved in the control of PHB synthesis, and of its metabolic relationships, has increased considerably, making way for new potential strategies for the further improvement of PHB production. Overall, the use of a multidisciplinary approach, integrating molecular and bioengineering aspects is a necessity for optimizing alginate and PHB production in A. vinelandii.
Collapse
Affiliation(s)
- Enrique Galindo
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional, Autónoma de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Carlos Peña
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional, Autónoma de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Cinthia Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma, de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Daniel Segura
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma, de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| | - Guadalupe Espín
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma, de México, Apdo. Post. 510-3 Cuernavaca, 62250, Morelos, México
| |
Collapse
|
57
|
Sabra W, Deckwer WD. Alginate—A Polysaccharide of Industrial Interest and Diverse Biological Functions. POLYSACCHARIDES 2004. [DOI: 10.1201/9781420030822.ch21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
58
|
Parente E, Piraino P, Fidaleo M, Moresi M. Overall volumetric oxygen transfer coefficient in an aerated bench-top stirred fermenter in aqueous dispersions of sodium alginate. Biotechnol Appl Biochem 2004; 40:133-43. [PMID: 15015940 DOI: 10.1042/ba20030213] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2003] [Revised: 03/05/2004] [Accepted: 03/12/2004] [Indexed: 11/17/2022]
Abstract
The dynamic gassing-out method was used to assess the effect of stirrer speed, air flow rate and alginate concentration on the overall volumetric oxygen mass transfer coefficient (K(L)a) in a bench-top stirred fermenter equipped with two Rushton-type turbines. As the alginate concentration in the medium was increased from 0 to 2% (w/v), the liquid film time constant (tau(F)) increased from approx. 30 to 300% of the electrode time constant (tau(E)), clearly showing that the liquid-probe diffusion film affected the oxygen-electrode response. By accounting for delayed probe response, liquid film time constant and gas residence time, the corrected values of K(L)a were empirically correlated with the above independent variables as converted into gassed power input and aeration number per unit liquid volume and the effective liquid/water shear viscosity ratio. Despite an average error of 19%, such a correlation might be useful to adjust the oxygen transfer in bench-top stirred reactors during viscous aerobic fermentations.
Collapse
Affiliation(s)
- Eugenio Parente
- Dipartimento di Biologia, Difesa e Biotecnologie Agro-Forestali, University of Basilicata, Campus di Macchia Romana, 85100 Potenza, Italy
| | | | | | | |
Collapse
|
59
|
Moresi M, Bruno M, Parente E. Viscoelastic properties of microbial alginate gels by oscillatory dynamic tests. J FOOD ENG 2004. [DOI: 10.1016/j.jfoodeng.2003.09.030] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
60
|
Selbmann L, Crognale S, Petruccioli M. Beta-glucan production by Botryosphaeria rhodina in different bench-top bioreactors. J Appl Microbiol 2004; 96:1074-81. [PMID: 15078524 DOI: 10.1111/j.1365-2672.2004.02241.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
AIMS Evaluation of the technical feasibility of transferring beta-glucan production by Botryosphaeria rhodina DABAC-P82 from shaken flasks to bench-top bioreactors. METHODS AND RESULTS Three different bioreactors were used: 3 l stirred tank reactor (STR-1) equipped with two different six-blade turbines; STR as above but equipped with a three-blade marine propeller plus draft-tube (STR-2); 2 l air-lift column reactor (ALR) equipped with an external loop. STR-1, tested at three different stirrer speeds (300, 500 and 700 rev min(-1)) appeared to be less suitable for beta-glucan production by the fungus, being maximum production (19.4 g l(-1)), productivity (0.42 g l(-1) h(-1)) and yield (0.48 g g(-1) of glucose consumed) markedly lower than those obtained in shaken culture (29.7 g l(-1), 1.23 g l(-1) h(-1) and 0.61 g g(-1), respectively). Better performances were obtained with both STR-2 and ALR. With the latter, in particular, the increase of production was accompanied by reduced fermentation time (25.7 g l(-1) after only 22 h); productivity and yield were highest (1.17 g l(-1) h(-1) and 0.62 g g(-1) of glucose consumed, respectively). CONCLUSION Using an air-lift reactor with external loop, the scaling up from shaken flasks to bench-top bioreactor of the beta-glucan production by B. rhodina DABAC-P82 is technically feasible. SIGNIFICANCE AND IMPACT OF THE STUDY Although culture conditions are still to be optimized, the results obtained using the ARL are highly promising.
Collapse
Affiliation(s)
- L Selbmann
- Dipartimento di Scienze Ambientali, University of Tuscia, Piazza dell'Università, Viterbo, Italy
| | | | | |
Collapse
|
61
|
Aquilanti L, Mannazzu I, Papa R, Cavalca L, Clementi F. Amplified ribosomal DNA restriction analysis for the characterization of Azotobacteraceae: a contribution to the study of these free-living nitrogen-fixing bacteria. J Microbiol Methods 2004; 57:197-206. [PMID: 15063060 DOI: 10.1016/j.mimet.2004.01.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Revised: 01/08/2004] [Accepted: 01/08/2004] [Indexed: 11/18/2022]
Abstract
A 16S rRNA gene-based fingerprinting method was developed for the identification of Azotobacteraceae and tested onto 48 soil isolates and 28 reference strains belonging to the free-living nitrogen-fixing bacterial group and to the most common species found in soil samples. According to this method, the 16S rRNA gene was amplified using universal primers for Eubacteria and PCR products were subsequently digested with RsaI, HhaI, HpaII, FnuDII, and AluI. The analysis of the restriction profiles obtained showed that the method is able to define a unique species-specific phylotype (SSP) for each of the eight Azotobacteraceae species tested. Cluster analysis was successfully employed for the identification of members of the family Azotobacteraceae, being assignation into species of the isolates confirmed by means of partial 16S rRNA gene sequencing.
Collapse
MESH Headings
- Cluster Analysis
- DNA, Bacterial/analysis
- DNA, Bacterial/chemistry
- DNA, Bacterial/isolation & purification
- DNA, Ribosomal/analysis
- DNA, Ribosomal/chemistry
- DNA, Ribosomal/isolation & purification
- Deoxyribonuclease HpaII/metabolism
- Deoxyribonucleases, Type II Site-Specific/metabolism
- Genes, rRNA
- Molecular Sequence Data
- Nitrogen Fixation
- Phylogeny
- Pseudomonadaceae/classification
- Pseudomonadaceae/genetics
- Pseudomonadaceae/isolation & purification
- Pseudomonadaceae/metabolism
- RNA, Ribosomal, 16S/analysis
- RNA, Ribosomal, 16S/genetics
- Ribotyping
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
- Soil Microbiology
Collapse
Affiliation(s)
- Lucia Aquilanti
- Dipartimento di Scienze degli Alimenti, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
| | | | | | | | | |
Collapse
|
62
|
Hansen EH, Albertsen L, Schäfer T, Johansen C, Frisvad JC, Molin S, Gram L. Curvularia haloperoxidase: antimicrobial activity and potential application as a surface disinfectant. Appl Environ Microbiol 2003; 69:4611-7. [PMID: 12902249 PMCID: PMC169116 DOI: 10.1128/aem.69.8.4611-4617.2003] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2002] [Accepted: 05/23/2003] [Indexed: 11/20/2022] Open
Abstract
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.
Collapse
|
63
|
Saude N, Chèze-Lange H, Beunard D, Dhulster P, Guillochon D, Cazé AM, Morcellet M, Junter GA. Alginate production by Azotobacter vinelandii in a membrane bioreactor. Process Biochem 2002. [DOI: 10.1016/s0032-9592(02)00090-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
64
|
Influence of Alginate Concentration and Molecular Weight on Functional Properties of Mayonnaise. Lebensm Wiss Technol 2002. [DOI: 10.1006/fstl.2002.0899] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
65
|
Selbmann L, Crognale S, Petruccioli M. Exopolysaccharide production from Sclerotium glucanicum NRRL 3006 and Botryosphaeria rhodina DABAC-P82 on raw and hydrolysed starchy materials. Lett Appl Microbiol 2002; 34:51-5. [PMID: 11849493 DOI: 10.1046/j.1472-765x.2002.01042.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIMS Evaluation of fermentative usage of raw starchy materials for exopolysaccharide (EPS) production by Sclerotium glucanicum NRRL 3006 and Botryosphaeria rhodina DABAC-P82. METHODS AND RESULTS Non-hydrolysed corn starch, soft wheat flour, potato flour, cassava flour, sweet and industrial potato flours, and corn starch hydrolysed to different dextrose equivalent (DE) were tested in shaken culture for EPS production. Both fungal strains produced EPS on all tested materials but the production was maximum on hydrolysed corn starch (30.5 and 19.8 g l(-1) by B. rhodina and S. glucanicum on corn starch at 100 and 62 DE, respectively). CONCLUSIONS Raw starchy materials as such and, in particular, partially or totally hydrolysed corn starch could be used profitably for EPS production by S. glucanicum and B. rhodina. SIGNIFICANCE AND IMPACT OF THE STUDY The excellent EPS production, productivity and yield of B. rhodina DABAC-P82 when grown on 60 g l(-1) of totally hydrolysed corn starch.
Collapse
Affiliation(s)
- L Selbmann
- Dipartimento di Agrobiologia e Agrochimica, University of Tuscia, Via San Camillo de Lellis, I-01100 Viterbo, Italy
| | | | | |
Collapse
|
66
|
Saude N, Junter GA. Production and molecular weight characteristics of alginate from free and immobilized-cell cultures of Azotobacter vinelandii. Process Biochem 2002. [DOI: 10.1016/s0032-9592(01)00298-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
67
|
High CO2 affects alginate production and prevents polymer degradation in cultures of Azotobacter vinelandii. Enzyme Microb Technol 2001. [DOI: 10.1016/s0141-0229(01)00435-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
68
|
Svanem BI, Strand WI, Ertesvag H, Skjåk-Braek G, Hartmann M, Barbeyron T, Valla S. The catalytic activities of the bifunctional Azotobacter vinelandii mannuronan C-5-epimerase and alginate lyase AlgE7 probably originate from the same active site in the enzyme. J Biol Chem 2001; 276:31542-50. [PMID: 11390391 DOI: 10.1074/jbc.m102562200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Azotobacter vinelandii genome encodes a family of seven secreted Ca(2+)-dependent epimerases (AlgE1--7) catalyzing the polymer level epimerization of beta-D-mannuronic acid (M) to alpha-L-guluronic acid (G) in the commercially important polysaccharide alginate. AlgE1--7 are composed of two types of protein modules, A and R, and the A-modules have previously been found to be sufficient for epimerization. AlgE7 is both an epimerase and an alginase, and here we show that the lyase activity is Ca(2+)-dependent and also responds similarly to the epimerases in the presence of other divalent cations. The AlgE7 lyase degraded M-rich alginates and a relatively G-rich alginate from the brown algae Macrocystis pyrifera most effectively, producing oligomers of 4 (mannuronan) to 7 units. The sequences cleaved were mainly G/MM and/or G/GM. Since G-moieties dominated at the reducing ends even when mannuronan was used as substrate, the AlgE7 epimerase probably stimulates the lyase pathway, indicating a complex interplay between the two activities. A truncated form of AlgE1 (AlgE1-1) was converted to a combined epimerase and lyase by replacing the 5'-798 base pairs in the algE1-1 gene with the corresponding A-module-encoding DNA sequence from algE7. Furthermore, substitution of an aspartic acid residue at position 152 with glycine in AlgE7A eliminated almost all of both the lyase and epimerase activities. Epimerization and lyase activity are believed to be mechanistically related, and the results reported here strongly support this hypothesis by suggesting that the same enzymatic site can catalyze both reactions.
Collapse
Affiliation(s)
- B I Svanem
- Department of Biotechnology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
| | | | | | | | | | | | | |
Collapse
|
69
|
Sabra W, Zeng AP, Lünsdorf H, Deckwer WD. Effect of oxygen on formation and structure of Azotobacter vinelandii alginate and its role in protecting nitrogenase. Appl Environ Microbiol 2000; 66:4037-44. [PMID: 10966426 PMCID: PMC92256 DOI: 10.1128/aem.66.9.4037-4044.2000] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2000] [Accepted: 06/06/2000] [Indexed: 11/20/2022] Open
Abstract
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.
Collapse
Affiliation(s)
- W Sabra
- Biochemical Engineering Division, Gesellschaft für Biotechnologische Forschung mbH, 38124 Braunschweig, Germany
| | | | | | | |
Collapse
|
70
|
Peña C, Trujillo-Roldán MA, Galindo E. Influence of dissolved oxygen tension and agitation speed on alginate production and its molecular weight in cultures of Azotobacter vinelandii*. Enzyme Microb Technol 2000; 27:390-398. [PMID: 10938418 DOI: 10.1016/s0141-0229(00)00221-0] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The alginate production by Azotobacter vinelandii, as well as the molecular weight of the polymer, are strongly influenced by the dissolved oxygen tension (DOT) and stirring speed of the culture. Under high DOT (5% of air saturation), the bacteria produced more alginate (4.5 g/l) than that obtained at low (0.5%) oxygen tension (1.0 g/l) in cultures conducted at 300 rpm. On the other hand, under constant DOT (3%), the higher the stirring speed (from 300 to 700 rev./min), the higher the specific growth rate and the alginate production rate. However, low agitation speed (300 rev./min) lead the culture to produce a polymer of high molecular weight (680 000 g/g mol) whereas a low molecular weight (352 000 g/g mol) alginate was isolated from cultures conducted at high (700 rev./min) stirring speed. At 700 rev./min, the MMW increased to a plateau between 1 and 3% DOT and then decreased to a minimum of 0.11 x 10(6) g/g mol at 7%. Microscopic observations revealed the presence of cell aggregates (one order of magnitude larger than individual cells) when the culture was conducted at 300 rev./min. Oxygen gradients occurring within the aggregates could be responsible of this phenomenon. At high agitation rate, the MMW of the alginate dropped towards the end of the culture in all conditions evaluated. Alginase activity was detected, which would be responsible for this phenomenon.
Collapse
Affiliation(s)
- C Peña
- Departamento de Bioingeniería, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Post. 510-3, Cuernavaca, 62250, Morelos, Mexico
| | | | | |
Collapse
|