TECNALIA Publications Repository :: Browsing by Keyword "Organic Chemistry"

Browsing by Keyword "Organic Chemistry"

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Additive Manufactured Scaffolds for Bone Tissue Engineering: Physical Characterization of Thermoplastic Composites with Functional Fillers: Physical Characterization of Thermoplastic Composites with Functional Fillers
(2021-08-13) Sinha, Ravi; Sanchez, Alberto; Camara-Torres, Maria; Uriszar-Aldaca, Iñigo Calderon; Calore, Andrea Roberto; Harings, Jules; Gambardella, Ambra; Ciccarelli, Lucia; Vanzanella, Veronica; Sisani, Michele; Scatto, Marco; Wendelbo, Rune; Perez, Sergio; Villanueva, Sara; Matanza, Amaia; Patelli, Alessandro; Grizzuti, Nino; Mota, Carlos; Moroni, Lorenzo; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN; Tecnalia Research & Innovation
Thermoplastic polymer–filler composites are excellent materials for bone tissue engineering (TE) scaffolds, combining the functionality of fillers with suitable load-bearing ability, biodegradability, and additive manufacturing (AM) compatibility of the polymer. Two key determinants of their utility are their rheological behavior in the molten state, determining AM processability and their mechanical load-bearing properties. We report here the characterization of both these physical properties for four bone TE relevant composite formulations with poly(ethylene oxide terephthalate)/poly(butylene terephthalate (PEOT/PBT) as a base polymer, which is often used to fabricate TE scaffolds. The fillers used were reduced graphene oxide (rGO), hydroxyapatite (HA), gentamicin intercalated in zirconium phosphate (ZrP-GTM) and ciprofloxacin intercalated in MgAl layered double hydroxide (MgAl-CFX). The rheological assessment showed that generally the viscous behavior dominated the elastic behavior (G″ > G′) for the studied composites, at empirically determined extrusion temperatures. Coupled rheological–thermal characterization of ZrP-GTM and HA composites showed that the fillers increased the solidification temperatures of the polymer melts during cooling. Both these findings have implications for the required extrusion temperatures and bonding between layers. Mechanical tests showed that the fillers generally not only made the polymer stiffer but more brittle in proportion to the filler fractions. Furthermore, the elastic moduli of scaffolds did not directly correlate with the corresponding bulk material properties, implying composite-specific AM processing effects on the mechanical properties. Finally, we show computational models to predict multimaterial scaffold elastic moduli using measured single material scaffold and bulk moduli. The reported characterizations are essential for assessing the AM processability and ultimately the suitability of the manufactured scaffolds for the envisioned bone regeneration application.
A brief review on industrial alternatives for the manufacturing of glycerol carbonate, a green chemical
(2012-03-16) Ochoa-Gómez, José R.; Gómez-Jiménez-Aberasturi, Olga; Ramírez-López, Camilo; Belsué, Mikel; Tecnalia Research & Innovation; BIOECONOMÍA Y CO2
Glycerol carbonate is one the glycerol derivatives which attracts attention for industrial applications. This review compares strategies for its synthesis, and their analyses lead to the conclusion that (indirect) procedures starting from glycerol- and/or CO 2-derivatives are the most attractive. These are described and compared, taking criteria of industrial feasibility into account. As a result, the transesterification of dimethyl carbonate or ethylene carbonate with glycerol using uncalcined CaO as catalyst appears to be currently the most suitable industrial process. Finally, potential applications of glycerol carbonate as a multifunctional compound are exemplified.
Bringing non-isocyanate polyurethanes closer to industrial implementation using carbonated soybean oil-based amino hardeners
(2023-12) Centeno-Pedrazo, Ander; Freixa, Zoraida; Feola, Roland; Lunzer, Florian; Garcia-Suarez, Eduardo J.; Ortiz, Pablo; Tecnalia Research & Innovation; BIOECONOMÍA Y CO2
The polyaddition between cyclic carbonates and diamines to form non-isocyanate polyurethanes (NIPUs) is a safer alternative than traditional PU synthesis. However, the lower reactivity of cyclic carbonates requires of long reaction times and/or high temperatures for their curing, hampering their industrial implementation in the coating industry. Starting from carbonated soybean oil (CSBO) and amine excess, and through a stepwise addition process, cyclic carbonate full conversion has been achieved, yielding amino-terminal NIPUs with up to 62 % of biobased content. These amino-terminal NIPUs act as regular amino hardeners, and have been used to cure epoxy resins under the time and temperature required by the coating industry. The performance of these partially bio-based, NIPU-epoxy hybrid coatings was evaluated by pot-life, drying, hardness and solvent resistance, achieving comparable results to the industrial formulations. The simple synthesis process, the suitable curing conditions and the properties of the coatings, bring NIPU chemistry closer to industrial implementation.
Chemicals from biomass: Synthesis of lactic acid by alkaline hydrothermal conversion of sorbitol
(2011-06) Ramírez-López, Camilo A.; Ochoa-Gómez, José R.; Gil-Río, Silvia; Gómez-Jiménez-Aberasturi, Olga; Torrecilla-Soria, Jesús; Tecnalia Research & Innovation; Laboratorio Químico; BIOECONOMÍA Y CO2; SG
BACKGROUND: Currently, the 'green chemistry' philosophy is being increasingly adopted by the chemical industry and, therefore, new production procedures of valuable chemicals from biomass-derived raw materials are being sought. In this work, the synthesis of lactic acid from sorbitol under alkaline hydrothermal conditions is investigated by analyzing the influence on conversions and yields of temperature, NaOH/sorbitol molar ratio (MR), initial sorbitol concentration (SC) and reaction time. RESULTS: A 100% sorbitol conversion and a maximum 39.5% yield of lactic acid on a carbon basis are obtained at 280 °C, 50 min, 1.0 mol L-1 SC and 2.0 MR. Glyceraldehyde was the only identified intermediate while formic acid, acrylic acid, acetic acid, oxalic acid and sodium carbonate were identified as over-oxidation products, all of them in very low yields with the exception of formic acid (16% yield at a MR of 4 and 280 °C). Several plausible conversion routes of sorbitol involving dehydrations, keto-enol tautomerisms, reverse aldol condensations, aldol condensations, Cannizzaro reactions and oxidations are proposed. CONCLUSIONS: Considering the high number of parallel conversion routes as a consequence of high functionality of sorbitol, the 39.5% lactic acid yield obtained is a good result. Total carbon mass in all identified products only justifies, at most, 50% of that in sorbitol due to the coexistence of several conversion routes resulting in a large number of products other than lactic acid.
Chemoselective epoxidation of dienes using polymer-supported manganese porphyrin catalysts
(2004-07-05) Brulé, Emile; De Miguel, Yolanda R.; Hii, King Kuok; Mercado
Manganese porphyrin catalysts supported on different polymer resins were assessed in the selective epoxidation of three dienes. The recyclability of the catalysts was examined.
Computational and Experimental Evaluation of the Immune Response of Neoantigens for Personalized Vaccine Design
(2023-05) Malaina, Iker; Gonzalez-Melero, Lorena; Martínez, Luis; Salvador, Aiala; Sanchez-Diez, Ana; Asumendi, Aintzane; Margareto, Javier; Carrasco-Pujante, Jose; Legarreta, Leire; García, María Asunción; Pérez-Pinilla, Martín Blas; Izu, Rosa; Martínez de la Fuente, Ildefonso; Igartua, Manoli; Alonso, Santos; Hernandez, Rosa Maria; Boyano, María Dolores; Genética
In the last few years, the importance of neoantigens in the development of personalized antitumor vaccines has increased remarkably. In order to study whether bioinformatic tools are effective in detecting neoantigens that generate an immune response, DNA samples from patients with cutaneous melanoma in different stages were obtained, resulting in a total of 6048 potential neoantigens gathered. Thereafter, the immunological responses generated by some of those neoantigens ex vivo were tested, using a vaccine designed by a new optimization approach and encapsulated in nanoparticles. Our bioinformatic analysis indicated that no differences were found between the number of neoantigens and that of non-mutated sequences detected as potential binders by IEDB tools. However, those tools were able to highlight neoantigens over non-mutated peptides in HLA-II recognition (p-value 0.03). However, neither HLA-I binding affinity (p-value 0.08) nor Class I immunogenicity values (p-value 0.96) indicated significant differences for the latter parameters. Subsequently, the new vaccine, using aggregative functions and combinatorial optimization, was designed. The six best neoantigens were selected and formulated into two nanoparticles, with which the immune response ex vivo was evaluated, demonstrating a specific activation of the immune response. This study reinforces the use of bioinformatic tools in vaccine development, as their usefulness is proven both in silico and ex vivo.
Correlations between rheological and thermal behaviour of TGDDM/m-PDA epoxy systems
(1994-05) Imaz, J. J.; Valea, A.; Cortazar, M.; Mondragon, I.; Centros PRE-FUSION TECNALIA - (FORMER)
Isothermal variation of viscosity has been investigated at various temperatures for an epoxy-aromatic amine system (TGDDM/m-PDA system). The variation of the extent of reaction during the curing process has been also determined by means of differential scanning calorimetry. Two different models were used to predict the viscosity during cure: a model based on a modified Williams-Landel-Ferry equation, and a percolation-gelation analogy. This analysis reflects that the reaction mechanism does not change with temperature in the studied range.
Development of self-contained microcapsules for optimised catalyst position in self-healing materials
(2020-01-20) Rodriguez, Raquel; Bekas, Dimitrios G.; Flórez, Sonia; Kosarli, Maria; Paipetis, Alkiviadis S.; POLIMEROS
Self-contained microcapsules for use in self-healing epoxy resin are successfully synthesized by suspension polymerization process. The microencapsulation of an epoxy resin using Polymethylmethacrylate (PMMA) as a shell material and the location of scandium triflate (Sc(OTf)3) as the catalyst into microcapsules shell during the microencapsulation processes is presented (PMMA/Sc(OTf)3-walled microcapsules). Spherical microcapsules of 80 μm in diameter with a liquid core content of 30 wt% (determined by HPLC) are produced. Catalyst location on microcapsules are assessed qualitatively by SEM-EADS and quantitatively by TGA showing high yields (⁓70 wt%). The evaluation of the healing efficiency was assessed in terms of fracture toughness recovery. PMMA/Sc(OTf)3-walled microcapsules showed an increased healing efficiency than that of conventional PMMA-walled capsule. The healing efficiency of the PMMA-walled capsules was 46.7 and 55.1% when the system healed at 80 and 120 °C, respectively. However, in the case of PMMA/Sc(OTf)3-walled microcapsules healing efficiency increased to 57.5 and 79.1% for the same healing temperatures.
Direct patterning of polymer optical periodic nanostructures on CYTOP for visible light waveguiding
(2018-08) Diez, M.; Raimbault, V.; Joly, S.; Oyhenart, L.; Doucet, J. B.; Obieta, I.; Dejous, C.; Bechou, L.; Tecnalia Research & Innovation
Optical waveguides and grating couplers based on polymer nanostructures are now considered as promising technologies for integrated biophotonic sensing systems. Commonly, structuration and patterning of polymers at the submicron scale requires the use of time and cost-consuming equipments such as electron beam lithography. Direct patterning of high refractive index polymer devices on CYTOP is now achievable and provides symmetric waveguides with top water-like claddings. In addition, transparency of polymers makes them suitable for operation in the visible range, being of major interest for biophotonic applications. In this paper, we report on the fabrication process of polymer submicronic single-mode waveguides on CYTOP for visible light operation. Sub-wavelength grating couplers with a pitch lower than 300 nm were fabricated to couple the input light into a 350 nm square cross-section waveguide. The whole device is imprinted in a single step using soft stamp lithography with a minimal residual layer. Finally, optical characterizations demonstrate a state-of-the-art transmission efficiency (around 1.5%) at the selected operating wavelength of 507 nm for different coupling angles in good agreement with simulations.
Effect of ethylene glycol dimethacrylate on VOC reduction, rheological, mechanical and anticorrosion properties of a hybrid sol-gel coating on AA2024-T3 and sulfuric acid anodized AA2024-T3
(2021-10) Agustín-Sáenz, Cecilia; Martín-Ugarte, Eider; Pérez-Allende, Beatriz; Izagirre-Etxeberria, Usoa; VALORIZACIÓN DE RESIDUOS; POLIMEROS; INGENIERÍA DE SUPERFICIES
An inorganic–organic coating based on methacrylic-functionalized silica and zirconia was synthesized by sol-gel technology as replacer of Cr(VI)-based treatments used to protect both unconverted and electrically converted AA2024-T3 for aeronautic application. The effect of a bi-methacrylate organic precursor in the formulation was studied with the aim to reduce the sol viscosity and coating thickness while crosslink was increased and volatile organic compounds (VOC) were diminished in the formulation. The viscoelastic behavior was studied by rheometry, and the properties of the coating material were related to its corrosion protection capability, studied by electrochemical impedance spectroscopy and neutral salt spray tests. The mechanical properties of the resulting coatings were studied by dynamic microindentation and rotary wear tests. The formulations containing the organic precursor provided coatings with higher degree of crosslinking and lower VOC. The derived coatings were thinner and provided outstanding corrosion protection with low thickness on unconverted AA2024-T3 and as sealant of hard sulfuric acid anodized AA2024-T3. The hardness was improved in comparison to coatings without the organic precursor although abrasion resistance was better for coatings with higher inorganic character.
Effect of the biobased polyols chemical structure on high performance thermoset polyurethane properties
(2022-12-16) Echeverria-Altuna, O.; Ollo, O.; Larraza, I.; Gabilondo, N.; Harismendy, I.; Eceiza, A.; POLIMEROS; Tecnalia Research & Innovation
The sustainability of the polymeric materials has become a fundamental challenge; therefore, the development of new biobased formulations has gained increasing interest. Thermoset polyurethanes (PURs) present high performance and are a competitive solution for structural composites. However, polyols used in the PUR synthesis are typically from petrochemical origin. Nowdays, a broad range of biobased polyols is available in the market, but there is not yet a specific formulation for high performance PURs composites. The aim of this work was to study the effect of biobased polyols' characteristics in the PUR processing and final properties. In addition, biobased polyol features to synthesize BIO-PURs suitable for structural applications were stablished. The viscosity and reactivity were studied by means of rheology and differential scanning calorimetry (DSC). Thermal and mechanical properties were studied through thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and flexural tests. The results obtained demonstrated the dramatic influence of polyols’ nature on BIO-PUR/PUR properties and their effect on the crosslink density. It was observed that using a high functionality and high hydroxyl index biobased polyol, it was possible to synthesize high performance BIO-PUR suitable for structural composites.
Effect of the catalyst system on the reactivity of a polyurethane resin system for RTM manufacturing of structural composites
(2022-03) Echeverria-Altuna, Oihane; Ollo, Olatz; Calvo-Correas, Tamara; Harismendy, Isabel; Eceiza, Arantxa; Tecnalia Research & Innovation; POLIMEROS
The high versatility of polyurethanes (PU’s) is encouraging the development of new formulations for new appli cations, like their use as a matrix for structural composites. PU’s based technology offers some advantages, such as fatigue resistance and fast curing cycles. However, their high reactivity hinders some manufacturing processes like Resin Transfer Moulding (RTM). This work aimed to achieve a PU resin (PUR) formulation with the required latency and reactivity for the RTM. For this purpose, different catalytic systems based on an epoxide and LiCl were investigated. The reactivity of the systems was evaluated through Differential Scanning Calorimetry (DSC) and rheology tests, and the curing reaction and viscosity were modelled. Furthermore, the RTM process of a representative composite part was simulated. Results demon strated the processability improvements when the LiCl was incorporated into the isocyanate component of the formulation combined with a monool or a diol. It was observed that these combinations contribute to the encapsulation of the LiCl between the as formed urethane groups by hydrogen bonding, providing the desired latency and acting as a delayed action catalyst. Once the reaction started and the encapsulation was deactivated, an alkoxide was formed to act as a catalyst. En capsulation was more effective with the diol, providing a higher latency.
Effects of Human and Porcine Adipose Extracellular Matrices Decellularized by Enzymatic or Chemical Methods on Macrophage Polarization and Immunocompetence
(2021-04-08) Cicuéndez, Mónica; Casarrubios, Laura; Feito, María José; Madarieta, Iratxe; Garcia-Urkia, Nerea; Murua, Olatz; Olalde, Beatriz; Briz, Nerea; Diez-Orejas, Rosalía; Portolés, María Teresa; Biomateriales; SG
The decellularized extracellular matrix (ECM) obtained from human and porcine adipose tissue (AT) is currently used to prepare regenerative medicine bio-scaffolds. However, the influence of these natural biomaterials on host immune response is not yet deeply understood. Since macrophages play a key role in the inflammation/healing processes due to their high functional plasticity between M1 and M2 phenotypes, the evaluation of their response to decellularized ECM is mandatory. It is also necessary to analyze the immunocompetence of macrophages after contact with decellularized ECM materials to assess their functional role in a possible infection scenario. In this work, we studied the effect of four decellularized adipose matrices (DAMs) obtained from human and porcine AT by enzymatic or chemical methods on macrophage phenotypes and fungal phagocytosis. First, a thorough biochemical characterization of these biomaterials by quantification of remnant DNA, lipids, and proteins was performed, thus indicating the efficiency and reliability of both methods. The proteomic analysis evidenced that some proteins are differentially preserved depending on both the AT origin and the decellularization method employed. After exposure to the four DAMs, specific markers of M1 proinflammatory and M2 anti-inflammatory macrophages were analyzed. Porcine DAMs favor the M2 phenotype, independently of the decellularization method employed. Finally, a sensitive fungal phagocytosis assay allowed us to relate the macrophage phagocytosis capability with specific proteins differentially preserved in certain DAMs. The results obtained in this study highlight the close relationship between the ECM biochemical composition and the macrophage’s functional role.
Emerging Reprocessable and Recyclable Biobased Cross-Linked Polyurethanes Through Diels-Alder Chemistry
(2024-04-26) Restrepo-Montoya, Ana C.; Larraza, Izaskun; Echeverria-Altuna, Oihane; Harismendy, Isabel; Saralegi, Ainara; Eceiza, Arantxa; POLIMEROS
Cross-linked polyurethanes (PUs) present outstanding properties and high versatility, making them ideal for use in many different applications. Nevertheless, the intersection of environmental and socioeconomic concerns regarding the recyclability of cross-linked materials presents alternative opportunities for advancing the field of cross-linked polyurethane chemistry. In this context, emerging reprocessable and recyclable biobased cross-linked PUs were synthesized within this work through Diels-Alder (DA) chemistry. Thus, a trifunctional partially biobased low-molecular-weight polyol containing the furan-maleimide Diels-Alder adduct (DA-triol) was developed to be used as a thermoreversible cross-linker in PU synthesis. First, the thermoreversibility of the cross-linker was demonstrated at temperatures as high as 160 °C (retro-DA reaction). Afterward, the DA-triol was used together with a commercial biobased macrodiol and polymeric methylene diphenyl diisocyanate (pMDI) to synthesize different formulations of PUs that ended up with properties ranging from flexible to rigid. Then, the recyclability and reprocessability of the synthesized PUs were also evaluated by compression, injection, and extrusion. Finally, the mechanical properties of the original and recycled polyurethanes were tested, obtaining recycling efficiencies higher than 80%. Thereby, these materials offer a solution to the long-standing issue of recycling of cross-linked polyurethanes, overcoming many sustainability challenges.
Enhancing Osteoconduction of PLLA-Based Nanocomposite Scaffolds for Bone Regeneration Using Different Biomimetic Signals to MSCs
(2012-02) Ciapetti, Gabriela; Granchi, Donatella; Devescovi, Valentina; Baglio, Serena R.; Leonardi, Elisa; Martini, Desirèe; Jurado, Maria Jesus; Olalde, Beatriz; Armentano, Ilaria; Kenny, Josè M.; Walboomers, Frank X.; Alava, J.I.; Baldini, Nicola; Tecnalia Research & Innovation; Biomateriales
In bone engineering, the adhesion, proliferation and differentiation of mesenchymal stromal cells rely on signaling from chemico-physical structure of the substrate, therefore prompting the design of mimetic “extracellular matrix”-like scaffolds. In this study, three-dimensional porous poly-L-lactic acid (PLLA)-based scaffolds have been mixed with different components, including single walled carbon nanotubes (CNT), micro-hydroxyapatite particles (HA), and BMP2, and treated with plasma (PT), to obtain four different nanocomposites: PLLA + CNT, PLLA + CNTHA, PLLA + CNT + HA + BMP2 and PLLA + CNT + HA + PT. Adult bone marrow mesenchymal stromal cells (MSCs) were derived from the femur of orthopaedic patients, seeded on the scaffolds and cultured under osteogenic induction up to differentiation and mineralization. The release of specific metabolites and temporal gene expression profiles of marrow-derived osteoprogenitors were analyzed at definite time points, relevant to in vitro culture as well asin vivo differentiation. As a result, the role of the different biomimetic components added to the PLLA matrix was deciphered, with BMP2-added scaffolds showing the highest biomimetic activity on cells differentiating to mature osteoblasts. The modification of a polymeric scaffold with reinforcing components which also work as biomimetic cues for cells can effectively direct osteoprogenitor cells differentiation, so as to shorten the time required for mineralization.
Enzymic hydrolysis of animal fats in organic solvents at temperatures below their melting points
(1991-05) Virto, M. D.; Lascaray, Jose Miguel; Solozabal, Rodolfo; de Renobales, Mertxe; Tecnalia Research & Innovation
Lipase from Candida rugosa catalyzed the hydrolysis of inedible beef tallow and pork lard (edible and inedible) in the presence of organic solvents at temperatures below the melting point of the fat. Reactions were carried out at 50% substrate with 180 lipase units per gram of fat in a two-liter reactor. In the presence of isooctane (5-10%) beef tallow yielded 94% hydrolysis in 24 hr both at 37° and 31°C. Edible pork lard yielded 97% hydrolysis under these conditions and at temperatures as low as 25°C, while inedible lard gave hydrolysis intermediate between the other two fats.
Fluidized Bed Membrane Reactors for Ultra Pure H2 Production - A Step forward towards Commercialization
(2016-03-19) Helmi, Arash; Fernandez, Ekain; Melendez, Jon; Pacheco Tanaka, David A.; Gallucci, Fausto; van Sint Annaland, Martin; TECNOLOGÍAS DE HIDRÓGENO; Tecnalia Research & Innovation; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOS
In this research the performance of a fluidized bed membrane reactor for high temperature water gas shift and its long term stability was investigated to provide a proof-of-concept of the new system at lab scale. A demonstration unit with a capacity of 1 Nm3/h of ultra-pure H2 was designed, built and operated over 900 h of continuous work. Firstly, the performance of the membranes were investigated at different inlet gas compositions and at different temperatures and H2 partial pressure differences. The membranes showed very high H2 fluxes (3.89E 6 mol m 2 Pa 1 s 1 at 400 C and 1 atm pressure difference) with a H2/N2 ideal perm-selectivity (up to 21,000 when integrating five membranes in the module) beyond the DOE 2015 targets. Monitoring the performance of the membranes and the reactor confirmed a very stable performance of the unit for continuous high temperature water gas shift under bubbling fluidization conditions. Several experiments were carried out at different temperatures, pressures and various inlet compositions to determine the optimum operating window for the reactor. The obtained results showed high hydrogen recovery factors, and very low CO concentrations at the permeate side (in average <10 ppm), so that the produced hydrogen can be directly fed to a low temperature PEM fuel cell.
High yield production of monomer-free chitosan oligosaccharides by pepsin catalyzed hydrolysis of a high deacetylation degree chitosan
(2007-12-28) Roncal, Tomás; Oviedo, Alberto; de Armentia, Iratxe López; Fernández, Laura; Villarán, M. Carmen; BIOECONOMÍA Y CO2; Alimentación Sostenible
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.
Highly Efficient Rh-catalysts Immobilised by π-π Stacking for the Asymmetric Hydroformylation of Norbornene under Continuous Flow Conditions
(2019-04-18) Cunillera, Anton; Blanco, Carolina; Gual, Aitor; Marinkovic, Jakob Maximilian; Garcia-Suarez, Eduardo J.; Riisager, Anders; Claver, Carmen; Ruiz, Aurora; Godard, Cyril; Tecnalia Research & Innovation
The application of C1-symmetrical diphosphite ligands containing furanose backbone in the Rh-catalysed asymmetric hydroformylation of norbornene is described. The catalysts were highly active and produced exclusively exo-norbornanecarboxaldehyde with enantioselectivities (ee) up to 71 %. Considering these promising results, the ligands were modified with a pyrene moiety to accomplish their immobilisation onto carbon materials. The corresponding Rh complexes bearing the novel pyrene-tagged ligands were synthesised and immobilised onto multiwalled carbon nanotubes (MWCNT), reduced graphene oxide (rGO) and carbon beads (CBs). The novel catalytic systems were tested in the asymmetric hydroformylation of norbornene providing similar performance in terms of both activity and selectivity compared to the non-immobilised systems. The recyclability of the new heterogenised catalysts was studied in the target reaction in batch mode. Nevertheless, the recycling was unsuccessful due to catalyst leaching. When used under continuous flow mode, these catalysts revealed robust and provided even higher ee than the corresponding homogeneous systems.
Modelling and control of the microstructure of comb-like poly(MAA-: Co-PEGMA) water-soluble copolymers
(2019-02-28) Emaldi, Inãki; Hamzehlou, Shaghayegh; Erkizia, Edurne; Sanchez Dolado, Jorge; Etxeberria, Agustin; Leiza, Jose Ramon; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN
Water-soluble copolymers of methacrylic acid and poly(ethylene glycol) methacrylate (poly(MAA-co-PEGMA)) present a comb like structure. These macromolecules under alkaline conditions present an anionic backbone and uncharged side chains. The control of their microstructure is of paramount importance for application as cementitious admixtures. With this in mind, open-loop control strategies including monomer starved and optimal addition policies were employed to obtain homogeneous composition copolymers. A detailed mathematical model was developed for the copolymerization of MAA and PEGMA5 and was used to develop optimal feeding strategies. The mathematical model provides a good representation of the experimental data sets and copolymers with desired homogeneous copolymer compositions were synthesized within the shortest possible reaction times.

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