The Experts below are selected from a list of 3291 Experts worldwide ranked by ideXlab platform
Carmen M Villaran - One of the best experts on this subject based on the ideXlab platform.
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high yield production of monomer free chitosan oligosaccharides by pepsin catalyzed hydrolysis of a high Deacetylation Degree chitosan
Carbohydrate Research, 2007Co-Authors: Tomas Roncal, Alberto Oviedo, Iratxe Lopez De Armentia, Laura Fernandez, Carmen M VillaranAbstract:Abstract The high molecular weight of chitosan, which results in a poor solubility at neutral pH values and high viscosity aqueous solutions, limits its potential uses in the fields of food, health and agriculture. However, most of these limitations are overcome by chitosan oligosaccharides obtained by enzymatic hydrolysis of the polymer. Several commercial enzymes with different original specificities were assayed for their ability to hydrolyze a 93% Deacetylation Degree chitosan and compared with a chitosanase. According to the patterns of viscosity decrease and reducing end formation, three enzymes—cellulase, pepsin and lipase A—were found to be particularly suitable for hydrolyzing chitosan at a level comparable to that achieved by chitosanase. Unlike the appreciable levels of both 2-amino-2-deoxy- d -glucose and 2-acetamido-2-deoxy- d -glucose monomers released from chitosan by the other enzymes after a 20 h-hydrolysis (4.6–9.1% of the total product weight), no monomer could be detected following pepsin cleavage. As a result, pepsin produced a higher yield of chitosan oligosaccharides than the other enzymes: 52% versus as much as 46%, respectively. Low molecular weight chitosans accounted for the remaining 48% of hydrolysis products. The calculated average polymerization Degree of the products released by pepsin was around 16 units after 20 h of hydrolysis. This product pattern and yield are proposed to be related to the bond cleavage specificity of pepsin and the high Deacetylation Degree of chitosan used as substrate. The optimal reaction conditions for hydrolysis of chitosan by pepsin were 40 °C and pH 4.5, and an enzyme/substrate ratio of 1:100 (w/w) for reactions longer than 1 h.
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high yield production of monomer free chitosan oligosaccharides by pepsin catalyzed hydrolysis of a high Deacetylation Degree chitosan
Carbohydrate Research, 2007Co-Authors: Tomas Roncal, Alberto Oviedo, Iratxe Lopez De Armentia, Laura Fernandez, Carmen M VillaranAbstract:The high molecular weight of chitosan, which results in a poor solubility at neutral pH values and high viscosity aqueous solutions, limits its potential uses in the fields of food, health and agriculture. However, most of these limitations are overcome by chitosan oligosaccharides obtained by enzymatic hydrolysis of the polymer. Several commercial enzymes with different original specificities were assayed for their ability to hydrolyze a 93% Deacetylation Degree chitosan and compared with a chitosanase. According to the patterns of viscosity decrease and reducing end formation, three enzymes--cellulase, pepsin and lipase A--were found to be particularly suitable for hydrolyzing chitosan at a level comparable to that achieved by chitosanase. Unlike the appreciable levels of both 2-amino-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-glucose monomers released from chitosan by the other enzymes after a 20h-hydrolysis (4.6-9.1% of the total product weight), no monomer could be detected following pepsin cleavage. As a result, pepsin produced a higher yield of chitosan oligosaccharides than the other enzymes: 52% versus as much as 46%, respectively. Low molecular weight chitosans accounted for the remaining 48% of hydrolysis products. The calculated average polymerization Degree of the products released by pepsin was around 16 units after 20h of hydrolysis. This product pattern and yield are proposed to be related to the bond cleavage specificity of pepsin and the high Deacetylation Degree of chitosan used as substrate. The optimal reaction conditions for hydrolysis of chitosan by pepsin were 40 Degrees C and pH 4.5, and an enzyme/substrate ratio of 1:100 (w/w) for reactions longer than 1h.
Rui L Reis - One of the best experts on this subject based on the ideXlab platform.
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marine collagen chitosan fucoidan cryogels as cell laden biocomposites envisaging tissue engineering
Biomedical Materials, 2020Co-Authors: Duarte Nuno Carvalho, L L Reys, Simone S Silva, Rui L Reis, Rita Lopezcebral, Rita O Sousa, Ana Luisa Alves, Miguel J Oliveira, Tiago H SilvaAbstract:The combination of marine origin biopolymers for tissue engineering (TE) applications is of high interest, due to their similarities with the proteins and polysaccharides present in the extracellular matrix of different human tissues. This manuscript reports on innovative collagen-chitosan-fucoidan cryogels formed by the simultaneous blending of these three marine polymers in a chemical-free crosslinking approach. The physicochemical characterization of marine biopolymers comprised FTIR, amino acid analysis, circular dichroism and SDS-PAGE, and suggested that the jellyfish collagen used in the cryogels was not denatured (preserved the triple helical structure) and had similarities with type II collagen. The chitosan presented a high Deacetylation Degree (90.1%) that can strongly influence the polymer physicochemical properties and biomaterial formation. By its turn, rheology, and SEM studies confirmed that these novel cryogels present interesting properties for TE purposes, such as effective blending of biopolymers without visible material segregation, mechanical stability (strong viscoelastic character), as well as adequate porosity to support cell proliferation and exchange of nutrients and waste products. Additionally, in vitro cellular assessments of all cryogel formulations revealed a non-cytotoxic behavior. The MTS test, live/dead assay and cell morphology assessment (phalloidin DAPI) showed that cryogels can provide a proper microenvironment for cell culturing, supporting cell viability and promoting cell proliferation. Overall, the obtained results suggest that the novel collagen-chitosan-fucoidan cryogels herein presented are promising scaffolds envisaging tissue engineering purposes, as both acellular biomaterials or cell-laden cryogels.
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influence of freezing temperature and Deacetylation Degree on the performance of freeze dried chitosan scaffolds towards cartilage tissue engineering
European Polymer Journal, 2017Co-Authors: L L Reys, Simone S Silva, Rogerio P Pirraco, Alexandra P Marques, Joao F Mano, Tiago H Silva, Rui L ReisAbstract:Abstract Chitosan-based porous structures have been significantly studied across the world as potential tissue engineering scaffolds. Despite the differences in chitosan produced from squid pens or crustacean shells, with the former being more reactive and easily available with a higher Degree of Deacetylation (DD), most of the studies report the use of crab or shrimp chitosan as they are readily available commercial sources. The aim of this work was to highlight the great potential of chitosan produced from squid pens for biomedical application. From freeze-dried scaffolds for soft tissue engineering, we investigated the influence of the DD of chitosan and the freezing temperature during processing on their performance. Chitosan was obtained by Deacetylation of β-chitin previously isolated from endoskeleton of giant squid Dosidicus gigas (DD 91.2%) and compared with a commercially available batch obtained from crab shells (DD 76.6%). Chitosan solutions were frozen at −80° C or −196° C and further freeze-dried to obtain 3D porous structures (scaffolds). Scaffolds prepared at −196° C have a compact structure with smaller pores, while those prepared at −80° C showed a lamellar structure with larger pores. The compressive modulus varied from 0.7 up to 8.8 MPa. Both types of scaffolds were stable on PBS, including in the presence of lysozyme, up to 4 weeks. Furthermore, the squid chitosan scaffolds processed at −80° C promoted ATDC5 chondrocyte-like cells adhesion and proliferation. The results suggest that the developed squid chitosan scaffolds might be further exploited for applications in cartilage tissue engineering.
Luiz Antonio De Almeida Pinto - One of the best experts on this subject based on the ideXlab platform.
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drying of chitosan in a spouted bed the influences of temperature and equipment geometry in powder quality
Lwt - Food Science and Technology, 2011Co-Authors: Guilherme Luiz Dotto, Vanderlei C Souza, Luiz Antonio De Almeida PintoAbstract:Abstract The influence of temperature and spouted bed geometry in drying chitosan with relation to powder quality (molecular weight, Deacetylation Degree, particle size, color) and operation characteristics (product recovery and mass accumulated) were investigated. Chitosan paste was obtained from shrimp wastes and dried in a spouted bed (slot-rectangular and conical-cylindrical geometries) with different inlet air temperatures (90, 100 and 110 °C). Thermogravimetric curves, infra-red analysis and scanning electron microscopy were carried out in order to verify powder quality. Chitosan paste used in drying experiments showed solid content 4%, molecular weight 140 kDa and Deacetylation Degree 85%. In all drying experiments Deacetylation Degree was not modified and final moisture content was in the commercial range (10%). Temperature increase caused an increase in molecular weight, powder darkening and increased particle size. The best powder quality was obtained in slot-rectangular spouted bed at 90 °C. In this condition product recovery was 65%, accumulated mass was 20% and the powder presented faint yellow coloration, high thermal stability and porous heterogeneous surface.
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Evaluation of molar weight and Deacetylation Degree of chitosan during chitin Deacetylation reaction: Used to produce biofilm
Chemical Engineering and Processing: Process Intensification, 2011Co-Authors: Catarina Motta De Moura, Jaqueline Motta De Moura, Niege Madeira Soares, Luiz Antonio De Almeida PintoAbstract:Abstract Chitosan is a polysaccharide derived from chitin, mainly of crustacean shells and shrimp wastes. The utilization of chitosan is related to the molar weight and Deacetylation Degree of the biopolymer. The aim of this work is to study the chitin Deacetylation reaction, by the viscosity average molar weight and Deacetylation Degree of chitosan as a function of reaction time. Deacetylation was carried out in concentrated alkaline solution, 421 g L −1 , at 130 °C and the reaction occurred during 4 h. Chitosan paste obtained after 20, 90 and 240 min was used to produce biofilms, which were characterized according water vapor permeability and mechanical properties (tensile strength and percentage tensile elongation at break). During the reaction time Deacetylation Degree reached 93%, and a 50% reduction in the viscosity average molar weight value in relation to the value of the first 20 min of reaction was found Both reactions presented a kinetic behavior of the pseudo-first order. Biofilm produced from the paste of chitosan with high Deacetylation Degree showed higher water vapor permeability (WVP), tensile strength (TS) and elongation ( E ) when compared to films with a low Deacetylation.
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adsorption of fd c red no 40 by chitosan isotherms analysis
Journal of Food Engineering, 2009Co-Authors: Jeferson Steffanello Piccin, Mery L G Vieira, Guilherme Luiz Dotto, Janaina Oliveira Goncalves, Luiz Antonio De Almeida PintoAbstract:The adsorption of azobenzene FD&C Red No. 40 (C.I. 16035) from aqueous solutions by chitosan was studied through adsorption isotherms. The effects of pH (5.7, 6.6 and 7.5), particle size ranges (0.10 ± 0.02, 0.18 ± 0.02 and 0.26 ± 0.02 mm), Deacetylation Degree (42 ± 5%, 64 ± 3% and 84 ± 3%) and temperature (25, 35 and 45 °C) were investigated. Langmuir, Freundlich and Redlich–Peterson (R–P) adsorption models were applied in order to describe the experimental isotherms and isotherm constants. Coefficients of determination (R2 > 0.95) and mean relative error (MRE < 0.10) values showed that Langmuir and R–P models presented better fit with the experimental data. The maximum monolayer adsorption value has been found to be 529 mg g−1, at pH 6.6, temperature 35 °C, particle size range 0.10 ± 0.02 mm, and Deacetylation Degree 84 ± 3%.
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optimization of Deacetylation in the production of chitosan from shrimp wastes use of response surface methodology
Journal of Food Engineering, 2007Co-Authors: Raquel Farias Weska, Jaqueline De Motta Moura, Lucia M Batista, Jaques Rizzi, Luiz Antonio De Almeida PintoAbstract:The use of chitosan in diverse areas is directly related to the polymer's molecular weight and Degree of Deacetylation, which depends on the conditions of chitin Deacetylation. The aim of the present study consisted of optimization of the Deacetylation stage in the production of chitosan, using the response surface methodology for the polymer's molecular weight. Chitin was obtained from shrimp wastes and the study of Deacetylation made through a factorial experimental design, where temperature and time were varied. The estimate of chitosan's intrinsic viscosity was made by linear regression with the values of reduced viscosity and concentration, using Huggins equation for polymers. The viscosity average molecular weight of chitosan was calculated for each experiment by the equation by Mark-Houwink-Sakurada that relates the intrinsic viscosity to the polymer's molecular weight. The optimum condition for the Deacetylation reaction for molecular weight was observed at a temperature of 130 °C and in 90 min, and corresponded to a molecular weight of chitosan of about 150 kDa, and a Deacetylation Degree of 90%.
Tomas Roncal - One of the best experts on this subject based on the ideXlab platform.
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high yield production of monomer free chitosan oligosaccharides by pepsin catalyzed hydrolysis of a high Deacetylation Degree chitosan
Carbohydrate Research, 2007Co-Authors: Tomas Roncal, Alberto Oviedo, Iratxe Lopez De Armentia, Laura Fernandez, Carmen M VillaranAbstract:Abstract The high molecular weight of chitosan, which results in a poor solubility at neutral pH values and high viscosity aqueous solutions, limits its potential uses in the fields of food, health and agriculture. However, most of these limitations are overcome by chitosan oligosaccharides obtained by enzymatic hydrolysis of the polymer. Several commercial enzymes with different original specificities were assayed for their ability to hydrolyze a 93% Deacetylation Degree chitosan and compared with a chitosanase. According to the patterns of viscosity decrease and reducing end formation, three enzymes—cellulase, pepsin and lipase A—were found to be particularly suitable for hydrolyzing chitosan at a level comparable to that achieved by chitosanase. Unlike the appreciable levels of both 2-amino-2-deoxy- d -glucose and 2-acetamido-2-deoxy- d -glucose monomers released from chitosan by the other enzymes after a 20 h-hydrolysis (4.6–9.1% of the total product weight), no monomer could be detected following pepsin cleavage. As a result, pepsin produced a higher yield of chitosan oligosaccharides than the other enzymes: 52% versus as much as 46%, respectively. Low molecular weight chitosans accounted for the remaining 48% of hydrolysis products. The calculated average polymerization Degree of the products released by pepsin was around 16 units after 20 h of hydrolysis. This product pattern and yield are proposed to be related to the bond cleavage specificity of pepsin and the high Deacetylation Degree of chitosan used as substrate. The optimal reaction conditions for hydrolysis of chitosan by pepsin were 40 °C and pH 4.5, and an enzyme/substrate ratio of 1:100 (w/w) for reactions longer than 1 h.
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high yield production of monomer free chitosan oligosaccharides by pepsin catalyzed hydrolysis of a high Deacetylation Degree chitosan
Carbohydrate Research, 2007Co-Authors: Tomas Roncal, Alberto Oviedo, Iratxe Lopez De Armentia, Laura Fernandez, Carmen M VillaranAbstract:The high molecular weight of chitosan, which results in a poor solubility at neutral pH values and high viscosity aqueous solutions, limits its potential uses in the fields of food, health and agriculture. However, most of these limitations are overcome by chitosan oligosaccharides obtained by enzymatic hydrolysis of the polymer. Several commercial enzymes with different original specificities were assayed for their ability to hydrolyze a 93% Deacetylation Degree chitosan and compared with a chitosanase. According to the patterns of viscosity decrease and reducing end formation, three enzymes--cellulase, pepsin and lipase A--were found to be particularly suitable for hydrolyzing chitosan at a level comparable to that achieved by chitosanase. Unlike the appreciable levels of both 2-amino-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-glucose monomers released from chitosan by the other enzymes after a 20h-hydrolysis (4.6-9.1% of the total product weight), no monomer could be detected following pepsin cleavage. As a result, pepsin produced a higher yield of chitosan oligosaccharides than the other enzymes: 52% versus as much as 46%, respectively. Low molecular weight chitosans accounted for the remaining 48% of hydrolysis products. The calculated average polymerization Degree of the products released by pepsin was around 16 units after 20h of hydrolysis. This product pattern and yield are proposed to be related to the bond cleavage specificity of pepsin and the high Deacetylation Degree of chitosan used as substrate. The optimal reaction conditions for hydrolysis of chitosan by pepsin were 40 Degrees C and pH 4.5, and an enzyme/substrate ratio of 1:100 (w/w) for reactions longer than 1h.
L L Reys - One of the best experts on this subject based on the ideXlab platform.
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marine collagen chitosan fucoidan cryogels as cell laden biocomposites envisaging tissue engineering
Biomedical Materials, 2020Co-Authors: Duarte Nuno Carvalho, L L Reys, Simone S Silva, Rui L Reis, Rita Lopezcebral, Rita O Sousa, Ana Luisa Alves, Miguel J Oliveira, Tiago H SilvaAbstract:The combination of marine origin biopolymers for tissue engineering (TE) applications is of high interest, due to their similarities with the proteins and polysaccharides present in the extracellular matrix of different human tissues. This manuscript reports on innovative collagen-chitosan-fucoidan cryogels formed by the simultaneous blending of these three marine polymers in a chemical-free crosslinking approach. The physicochemical characterization of marine biopolymers comprised FTIR, amino acid analysis, circular dichroism and SDS-PAGE, and suggested that the jellyfish collagen used in the cryogels was not denatured (preserved the triple helical structure) and had similarities with type II collagen. The chitosan presented a high Deacetylation Degree (90.1%) that can strongly influence the polymer physicochemical properties and biomaterial formation. By its turn, rheology, and SEM studies confirmed that these novel cryogels present interesting properties for TE purposes, such as effective blending of biopolymers without visible material segregation, mechanical stability (strong viscoelastic character), as well as adequate porosity to support cell proliferation and exchange of nutrients and waste products. Additionally, in vitro cellular assessments of all cryogel formulations revealed a non-cytotoxic behavior. The MTS test, live/dead assay and cell morphology assessment (phalloidin DAPI) showed that cryogels can provide a proper microenvironment for cell culturing, supporting cell viability and promoting cell proliferation. Overall, the obtained results suggest that the novel collagen-chitosan-fucoidan cryogels herein presented are promising scaffolds envisaging tissue engineering purposes, as both acellular biomaterials or cell-laden cryogels.
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influence of freezing temperature and Deacetylation Degree on the performance of freeze dried chitosan scaffolds towards cartilage tissue engineering
European Polymer Journal, 2017Co-Authors: L L Reys, Simone S Silva, Rogerio P Pirraco, Alexandra P Marques, Joao F Mano, Tiago H Silva, Rui L ReisAbstract:Abstract Chitosan-based porous structures have been significantly studied across the world as potential tissue engineering scaffolds. Despite the differences in chitosan produced from squid pens or crustacean shells, with the former being more reactive and easily available with a higher Degree of Deacetylation (DD), most of the studies report the use of crab or shrimp chitosan as they are readily available commercial sources. The aim of this work was to highlight the great potential of chitosan produced from squid pens for biomedical application. From freeze-dried scaffolds for soft tissue engineering, we investigated the influence of the DD of chitosan and the freezing temperature during processing on their performance. Chitosan was obtained by Deacetylation of β-chitin previously isolated from endoskeleton of giant squid Dosidicus gigas (DD 91.2%) and compared with a commercially available batch obtained from crab shells (DD 76.6%). Chitosan solutions were frozen at −80° C or −196° C and further freeze-dried to obtain 3D porous structures (scaffolds). Scaffolds prepared at −196° C have a compact structure with smaller pores, while those prepared at −80° C showed a lamellar structure with larger pores. The compressive modulus varied from 0.7 up to 8.8 MPa. Both types of scaffolds were stable on PBS, including in the presence of lysozyme, up to 4 weeks. Furthermore, the squid chitosan scaffolds processed at −80° C promoted ATDC5 chondrocyte-like cells adhesion and proliferation. The results suggest that the developed squid chitosan scaffolds might be further exploited for applications in cartilage tissue engineering.