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Jack Legrand - One of the best experts on this subject based on the ideXlab platform.
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a new process for extracting Alginates from laminaria digitata reactive extrusion
Food and Bioprocess Technology, 2008Co-Authors: Peggy Vauchel, Abdellah Arhaliass, Regis Baron, Raymond Kaas, Jack LegrandAbstract:Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The main step in the extraction protocol used in the alginate industry is that of alkaline extraction. A batch process is used for this step, which is time-, water-, and reactant-consuming. The possibility of extracting by reactive extrusion was investigated. The reactive extrusion process appeared to be more efficient than the batch process for the alkaline extraction of Alginates from Laminaria digitata in several key ways: Time demand is reduced from about an hour to only few minutes, water and reactant requirements are divided by more than a factor 2, extraction yield is 15% higher (relative enhancement), and the rheological properties of the product were all enhanced. Hence, reactive extrusion could be an interesting alternative process for the alginate industry to produce high rheological properties Alginates.
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A new process for the extraction of Alginates from Laminaria digitata : reactive extrusion
Food and Bioprocess Technology, 2008Co-Authors: Peggy Vauchel, Abdellah Arhaliass, Regis Baron, Raymond Kaas, Jack LegrandAbstract:Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The main step in the extraction protocol used in the alginate industry is that of alkaline extraction. A batch process is used for this step, which is time-, water-, and reactant-consuming. The possibility of extracting by reactive extrusion was investigated. The reactive extrusion process appeared to be more efficient than the batch process for the alkaline extraction of Alginates from Laminaria digitata in several key ways: Time demand is reduced from about an hour to only few minutes, water and reactant requirements are divided by more than a factor 2, extraction yield is 15% higher (relative enhancement), and the rheological properties of the product were all enhanced. Hence, reactive extrusion could be an interesting alternative process for the alginate industry to produce high rheological properties Alginates.
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Decrease in dynamic viscosity and average molecular weight of alginate from Laminaria digitata during alkaline extraction
Journal of Phycology, 2008Co-Authors: Peggy Vauchel, Abdellah Arhaliass, Raymond Kaas, Jack Legrand, Regis BaronAbstract:Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The central step in the extraction protocol used in the alginate industry is the alkaline extraction, which requires several hours. In this study, a significant decrease in alginate dynamic viscosity was observed after 2 h of alkaline treatment. Intrinsic viscosity and average molecular weight of Alginates from alkaline extractions 1–4 h in duration were determined, indicating depolymerization of Alginates: average molecular weight decreased significantly during the extraction, falling by a factor of 5 between 1 and 4 h of extraction. These results suggested that reducing extraction time could enable preserving the rheological properties of the extracted Alginates.
Kijung Paeng - One of the best experts on this subject based on the ideXlab platform.
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effect of calcium ion cross linker concentration on porosity surface morphology and thermal behavior of calcium Alginates prepared from algae undaria pinnatifida
Carbohydrate Polymers, 2010Co-Authors: Tara Sankar Pathak, Kijung PaengAbstract:Abstract Alginic acid and metal (sodium) Alginates was prepared from fresh algae using hot extraction method. Calcium Alginates are also prepared from sodium alginate by varying calcium ion (calcium chloride) concentrations. FTIR spectra indicate that alginic acid is converted into metal alginate. Surface morphology as well as total intrusion volume, porosity (%) and pore size distribution changes by changing calcium ion (cross-linker) concentrations. Thermal degradation of calcium Alginates showed a stepwise weight loss during thermal sweep, indicating different types of reactions during degradation. Calcium alginate (Calg0.6) prepared at low calcium ion concentration is least stable whereas at highest calcium ion concentration, the alginate sample (Calg20) is most stable at final degradation temperature (800 °C). Kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered as four consecutive 1st order reactions.
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effect of cross linker and cross linker concentration on porosity surface morphology and thermal behavior of metal Alginates prepared from algae undaria pinnatifida
Carbohydrate Polymers, 2009Co-Authors: Tara Sankar Pathak, Daejin Baek, Kijung PaengAbstract:Abstract Alginic acid and metal Alginates are prepared from fresh algae using extraction method. FTIR spectra indicate that alginic acid is converted into metal alginate. Asymmetric stretching of free carboxyl group of zinc alginate at 1596 cm −1 is shifted to 1582 cm −1 in cadmium alginate, due to the change of charge density, radius and atomic weight of the cation. Surface morphology changes by changing the cross-linker and cross-linker concentration at same magnification. Total intrusion volume, porosity (%) and pore size distribution also changes by changing cross-linker and cross-linker concentration. Thermal degradation results reveals that zinc and cadmium Alginates started decomposing at 100 °C, but rapid degradation started around 300 °C and showed a stepwise weight loss during thermal sweep, indicating different types of reactions during degradation. Kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered as two or three consecutive 1st order reactions.
Peggy Vauchel - One of the best experts on this subject based on the ideXlab platform.
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a new process for extracting Alginates from laminaria digitata reactive extrusion
Food and Bioprocess Technology, 2008Co-Authors: Peggy Vauchel, Abdellah Arhaliass, Regis Baron, Raymond Kaas, Jack LegrandAbstract:Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The main step in the extraction protocol used in the alginate industry is that of alkaline extraction. A batch process is used for this step, which is time-, water-, and reactant-consuming. The possibility of extracting by reactive extrusion was investigated. The reactive extrusion process appeared to be more efficient than the batch process for the alkaline extraction of Alginates from Laminaria digitata in several key ways: Time demand is reduced from about an hour to only few minutes, water and reactant requirements are divided by more than a factor 2, extraction yield is 15% higher (relative enhancement), and the rheological properties of the product were all enhanced. Hence, reactive extrusion could be an interesting alternative process for the alginate industry to produce high rheological properties Alginates.
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A new process for the extraction of Alginates from Laminaria digitata : reactive extrusion
Food and Bioprocess Technology, 2008Co-Authors: Peggy Vauchel, Abdellah Arhaliass, Regis Baron, Raymond Kaas, Jack LegrandAbstract:Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The main step in the extraction protocol used in the alginate industry is that of alkaline extraction. A batch process is used for this step, which is time-, water-, and reactant-consuming. The possibility of extracting by reactive extrusion was investigated. The reactive extrusion process appeared to be more efficient than the batch process for the alkaline extraction of Alginates from Laminaria digitata in several key ways: Time demand is reduced from about an hour to only few minutes, water and reactant requirements are divided by more than a factor 2, extraction yield is 15% higher (relative enhancement), and the rheological properties of the product were all enhanced. Hence, reactive extrusion could be an interesting alternative process for the alginate industry to produce high rheological properties Alginates.
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Decrease in dynamic viscosity and average molecular weight of alginate from Laminaria digitata during alkaline extraction
Journal of Phycology, 2008Co-Authors: Peggy Vauchel, Abdellah Arhaliass, Raymond Kaas, Jack Legrand, Regis BaronAbstract:Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The central step in the extraction protocol used in the alginate industry is the alkaline extraction, which requires several hours. In this study, a significant decrease in alginate dynamic viscosity was observed after 2 h of alkaline treatment. Intrinsic viscosity and average molecular weight of Alginates from alkaline extractions 1–4 h in duration were determined, indicating depolymerization of Alginates: average molecular weight decreased significantly during the extraction, falling by a factor of 5 between 1 and 4 h of extraction. These results suggested that reducing extraction time could enable preserving the rheological properties of the extracted Alginates.
Enrique Galindo - One of the best experts on this subject based on the ideXlab platform.
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molecular weight and viscosifying power of Alginates produced in azotobacter vinelandii cultures in shake flasks under low power input
Journal of Chemical Technology & Biotechnology, 2016Co-Authors: Karen Gomezpazarin, Enrique Galindo, Celia Flores, Tania Castillo, Jochen Buchs, Carlos PenaAbstract:BACKGROUND The aim of this study was to evaluate the viscosifying power and mean molecular weight (MMW) of alginate synthesized by Azotobacter vinelandii in a region of very low power input; as well as to scale-up the process of alginate production in a 3 L fermenter using the power input profile (determined in shake flasks) as criterion. RESULTS In cultures developed at very low power input (P/V) (0.02 to 0.68 kW m−3) and maximal oxygen transfer rate (OTRmax) from to 0.85 to 2.8 mmol L-1 h-1, both the specific growth rate and alginate production were negatively affected. In contrast, the viscosifying power of the alginate increased significantly, with respect to that obtained at the highest power input (1.6 kW m−3). This behavior was related to the synthesis of Alginates with a high MMW (2240 kDa). When profiles of power input determined in shake flasks at very low P/V were reproduced in a stirred fermentor, it was possible to reproduce the same trends in both the alginate production and the polymer viscosifying power. CONCLUSION This study provides useful information in order to implement new scale-up strategies for alginate production, exhibiting chemical characteristics and viscosifying properties superior to commercial Alginates. © 2015 Society of Chemical Industry
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expression of alginases and alginate polymerase genes in response to oxygen and their relationship with the alginate molecular weight in azotobacter vinelandii
Enzyme and Microbial Technology, 2013Co-Authors: Celia Flores, Carlos Pena, Soledad Moreno, Guadalupe Espin, Enrique GalindoAbstract:Abstract The transcription of genes involved in alginate polymerization and depolymerization, as well as the alginase activity (extracellular and intracellular) under oxygen-limited and non oxygen-limited conditions in cultures of A. vinelandii , was studied. Two levels of dissolved oxygen tension (DOT) (1% and 5%, oxygen-limited and non-oxygen-limited, respectively) strictly controlled by gas blending, were evaluated in a wild type strain. In cultures at low DOT (1%), in which a high molecular weight alginate (1200 kDa) was synthesized, the transcription levels of alg8 and alg44 (genes encoding alginate polymerase complex), and algX (encoding a protein involved in polymer transport through periplasmic space) were considerably higher as compared to cultures conducted at 5% DOT, under which an alginate with a low MW (42 kDa) was produced. In the case of genes encoding for intracellular and extracellular alginases, the levels of these transcripts were higher at 1% DOT. However, intracellular and extracellular alginase activity were lower (0.017 and 0.01 U/mg protein, respectively) in cultures at 1% DOT, as compared with the activities measured at 5% DOT (0.027 and 0.052 U/mg protein for intracellular and extracellular maximum activity, respectively). The low alginase activity measured in cultures at 1% DOT and the high level of transcription of genes constituting alginate polymerase complex might be mechanisms by which oxygen regulates the production of Alginates with a high MW.
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the acetylation degree of Alginates in azotobacter vinelandii atcc9046 is determined by dissolved oxygen and specific growth rate studies in glucose limited chemostat cultivations
Journal of Industrial Microbiology & Biotechnology, 2013Co-Authors: Tania Castillo, Enrique Galindo, Carlos PenaAbstract:Alginates are polysaccharides that may be used as viscosifiers and gel or film-forming agents with a great diversity of applications. The Alginates produced by bacteria such as Azotobacter vinelandii are acetylated. The presence of acetyl groups in this type of alginate increases its solubility, viscosity, and swelling capability. The aim of this study was to evaluate, in glucose-limited chemostat cultivations of A. vinelandii ATCC9046, the influence of dissolved oxygen tension (DO) and specific growth rate (μ) on the degree of acetylation of Alginates produced by this bacterium. In glucose-limited chemostat cultivations, the degree of alginate acetylation was evaluated under two conditions of DO (1 and 9 %) and for a range of specific growth rates (0.02–0.15 h−1). In addition, the alginate yields and PHB production were evaluated. High DO in the culture resulted in a high degree of alginate acetylation, reaching a maximum acetylation degree of 6.88 % at 9 % DO. In contrast, the increment of μ had a negative effect on the production and acetylation of the polymer. It was found that at high DO (9 %) and low μ, there was a reduction of the respiration rate, and the PHB accumulation was negligible, suggesting that the flux of acetyl-CoA (the acetyl donor) was diverted to alginate acetylation.
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specific growth rate determines the molecular mass of the alginate produced by azotobacter vinelandii
Biochemical Engineering Journal, 2005Co-Authors: Ruben Priegojimenez, Carlos Pena, Octavio T Ramirez, Enrique GalindoAbstract:Abstract A mutant strain (SML2) of Azotobacter vinelandii , unable to produce alginases, was grown in exponentially fed-batch cultures under constant dissolved oxygen tension and using washed-cells inocula. Using this culture technique, a pseudo-stationary steady state was achieved at specific growth rates ( μ ) of 0.03 ± 0.009, 0.06 ± 0.013 and 0.09 ± 0.012 h −1 . A batch culture, which developed a μ of 0.21 h −1 , was also performed. The mean molecular mass (MMM) of the alginate increased as μ decreased, and this dependence was particularly pronounced at μ below 0.09 h −1 . The MMM obtained at 0.03 h −1 was 15 times higher (1300 ± 150 kDa) than in batch culture (95 ± 8 kDa). At the lowest μ tested (0.03 h −1 ± 0.009 h −1 ), the alginate yield on biomass (Yp/x) was about twice that observed at μ above 0.06 ± 0.013 h −1 . This study shows that the MMM of bacterial alginate can be maximized by a simple strategy of growth rate control. Furthermore, production of high MMM Alginates might be a bacterial response to cope with substrate shortages.
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the roles of oxygen and alginate lyase in determining the molecular weight of alginate produced by azotobacter vinelandii
Applied Microbiology and Biotechnology, 2004Co-Authors: Mauricio A Trujilloroldan, Soledad Moreno, Guadalupe Espin, Enrique GalindoAbstract:An Azotobacter vinelandii mutant lacking alginate-lyase (SML2) and the wild type (ATCC 9046) were used to discriminate between the roles of the polymerase complex and alginate-lyase in the synthesis of alginate in cultures conducted under controlled dissolved oxygen tension (DOT). To avoid the presence of pre-synthesized Alginates, all cultures were inoculated with washed cells. For cultures carried out at 3% DOT using the mutant, a well defined family of Alginates of high mean molecular weight (MMW) were obtained (985 kDa). Under 1% and 5% DOT, the mutant produced unique families of Alginates with lower MMW (150 and 388 kDa). A similar behavior was observed using the wild type: a production of well defined families of Alginates of high MMW at 3% DOT (1,250 kDa) and lower MMW at 1% and 5% DOT (370 and 350 kDa). At the end of the ATCC 9046 fermentations, alginate was depolymerized by the action of lyases. Overall, the evidence indicated that polymerization of alginate is carried out by producing families of polysaccharide in a narrow MMW range, and that it is highly dependent on DOT. The role of alginate-lyase (present in the wild type) is restricted to a post-polymerization step.
Regis Baron - One of the best experts on this subject based on the ideXlab platform.
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a new process for extracting Alginates from laminaria digitata reactive extrusion
Food and Bioprocess Technology, 2008Co-Authors: Peggy Vauchel, Abdellah Arhaliass, Regis Baron, Raymond Kaas, Jack LegrandAbstract:Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The main step in the extraction protocol used in the alginate industry is that of alkaline extraction. A batch process is used for this step, which is time-, water-, and reactant-consuming. The possibility of extracting by reactive extrusion was investigated. The reactive extrusion process appeared to be more efficient than the batch process for the alkaline extraction of Alginates from Laminaria digitata in several key ways: Time demand is reduced from about an hour to only few minutes, water and reactant requirements are divided by more than a factor 2, extraction yield is 15% higher (relative enhancement), and the rheological properties of the product were all enhanced. Hence, reactive extrusion could be an interesting alternative process for the alginate industry to produce high rheological properties Alginates.
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A new process for the extraction of Alginates from Laminaria digitata : reactive extrusion
Food and Bioprocess Technology, 2008Co-Authors: Peggy Vauchel, Abdellah Arhaliass, Regis Baron, Raymond Kaas, Jack LegrandAbstract:Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The main step in the extraction protocol used in the alginate industry is that of alkaline extraction. A batch process is used for this step, which is time-, water-, and reactant-consuming. The possibility of extracting by reactive extrusion was investigated. The reactive extrusion process appeared to be more efficient than the batch process for the alkaline extraction of Alginates from Laminaria digitata in several key ways: Time demand is reduced from about an hour to only few minutes, water and reactant requirements are divided by more than a factor 2, extraction yield is 15% higher (relative enhancement), and the rheological properties of the product were all enhanced. Hence, reactive extrusion could be an interesting alternative process for the alginate industry to produce high rheological properties Alginates.
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Decrease in dynamic viscosity and average molecular weight of alginate from Laminaria digitata during alkaline extraction
Journal of Phycology, 2008Co-Authors: Peggy Vauchel, Abdellah Arhaliass, Raymond Kaas, Jack Legrand, Regis BaronAbstract:Alginates are natural polysaccharides that are extracted from brown seaweeds and widely used for their rheological properties. The central step in the extraction protocol used in the alginate industry is the alkaline extraction, which requires several hours. In this study, a significant decrease in alginate dynamic viscosity was observed after 2 h of alkaline treatment. Intrinsic viscosity and average molecular weight of Alginates from alkaline extractions 1–4 h in duration were determined, indicating depolymerization of Alginates: average molecular weight decreased significantly during the extraction, falling by a factor of 5 between 1 and 4 h of extraction. These results suggested that reducing extraction time could enable preserving the rheological properties of the extracted Alginates.
