Departamento de Ingeniería Química, Ambiental y de los Materiales

URI permanente para esta comunidadhttps://hdl.handle.net/10953/42

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Reaction sintered Al2O3/Al2TiO5 microcrack-free composites obtained by colloidal ﬁltration
(Elsevier, 2004) Bueno, Salvador; Moreno-Botella, Rodrigo; Baudín, Carmen
Dense and microcrack-free Al2O3 / Al2TiO5 composites (10, 30 and 40 vol. % of Al2TiO5) have been obtained by colloidal filtration and reaction sintering, using alumina and titania as starting powders. The processing of the composites has been studied focusing on the rheological behaviour of aqueous suspensions of each powder and of mixtures. Colloidal filtration of optimised suspensions, with a solid loading as high as 50 vol. %, and a thermal treatment at 1450ºC, lead to completely reacted and uncracked sintered materials with homogeneously distributed aluminium titanate contents up to 40 vol. % and high density. Thermal diffusivity values from 25 to 800ºC are coincident on heating and cooling for the three studied composites, and decrease with temperature and with aluminium titanate content.
Design and processing of Al2O3–Al2TiO5 layered structures
(Elsevier, 2005) Bueno, Salvador; Moreno-Botella, Rodrigo; Baudín, Carmen
Al2O3-Al2TiO5 layered composites were manufactured by a colloidal route from aqueous Al2O3 and TiO2 suspensions with 50vol.% solids. The mechanical behaviours of individual monolithic composite materials were combined and taken as basis for the design of the layered structures. Residual stresses which are likely to occur due to processing and thermally introduced misfits were calculated and considered for the manufacture of the laminates. Monoliths with 10, 30 and 40 vol.% of second phase showed that increasing proportions of aluminium titanate decrease strength and increase the non-linear behaviour. In order to obtain the desired combination of mechanical behaviours of the layers, two laminate designs with external and central layers of one composition and the alternating internal layer of the other composition were chosen taking into account chemical compatibility and development of residual stresses. In the system AA10, external and central layers of monophase Al2O3 with high strength were combined with intermediate layers of Al2O3 with 10vol.% of Al2TiO5. The system A10A40 was selected to combine low strength and energy absorbing intermediate layers of Al2O3 with 40vol.% of Al2TiO5 and sufficient strength provided by external layers of Al2O3 with 10vol.% of Al2TiO5. The stress-strain behaviour of the laminates was linear up to their failure stresses, with apparent strain for zero load after fracture larger than that corresponding the monoliths of the same composition as that of the external layers. Moreover, the stress drop of the laminate samples occurred in step-like form thus suggesting the occurrence of additional energy consuming processes during fracture.
Layered materials with high strength and ﬂaw tolerance based on alumina and aluminium titanate
(Elsevier, 2007) Bueno, Salvador; Baudín, Carmen
Laminates in which high strength external layers and flaw tolerant internal layers with similar compositions are combined, can provide improved mechanical behavior in relation to that of monolithic materials with the same composition as the layers. The limitation of this design, in which no residual stresses are present, is the difficulty that involves the co-sintering of layers with large microstructural differences in the green state. This work describes a new method to obtain laminates constituted by layers with large differences in terms of grain size starting from green bodies with similar microstructures. The approach is based on the effect of small amounts of titania as agents for alumina grain growth enhancement. Starting from fine grained green bodies that combined alumina layers with composite layers made of mixtures of alumina and titania, additional "in situ" formed layers constituted by large (≅20-30µm) alumina grains were found after sintering contiguous to the composite layers. The thickness of the "in situ" formed layers reached up to 200 µm, depending on the thermal treatment (1450-1550ºC). The fracture behaviour of the laminates and the monoliths was studied, using stable SEVNB (Single Edge V Notched Beam) tests, in terms of work of fracture and the critical stress intensity factor in mode I, KIC. The large grain sized alumina layers reinforced the laminates by crack branching and bridging.
Fracture behaviour of microcrack-free alumina-aluminium titanate ceramics with second phase nanoparticles at alumina grain boundaries
(Elsevier, 2008) Bueno, Salvador; M. Helene, Berger; Moreno, Rodrigo
Non-destructive characterization of alumina/aluminium titanate composites using a micromechanical model and ultrasonic determinations. Part I. Evaluation of the effective elastic constants of aluminium titanate.
(Elsevier, 2008) Bueno, Salvador; González-Hernández, Margarita; Sánchez-Martín, Teresa; Anaya-Velayos, José Javier; Baudín, Carmen
A method to evaluate the elastic constants of aluminium titanate in alumina/aluminium titanate composites is described. Results are derived from a three-phase micromechanical model proposed to relate the velocity of propagation of ultrasounds in the materials with their microstructural characteristics and the elastic behaviour of the constituents. Dense and un-cracked alumina and alumina + 10 vol.% aluminium titanate specimens have been fabricated by colloidal processing and the longitudinal and transverse ultrasound velocities have been determined by the ultrasonic jointly pulse-echo and transmission ultrasound immersion techniques, employing a digital signal processing. In order to assure the adequacy of the proposed method, results for monophase alumina have been compared to those obtained from the resonance frequencies of high density alumina plates tested in flexure and shear. The values of elastic moduli obtained using the two methods were coincident, which assured the validity of the non destructive proposed method.
Reduced strength degradation of alumina-aluminium titanate composite subjected to low-velocity impact loading
(Elsevier, 2008) Bueno, Salvador; Micele, Lorenzo; Baudín, Carmen; de-Portu, Goffredo
The impact behaviour of monophase alumina and alumina-aluminium titanate monolithic composite ceramics that present flaw tolerant behaviour was studied. Low-velocity impact loading tests were performed on bending bars and the residual strength after the impact was evaluated by 4-point bending tests. The impact tests were monitored using an instrumented drop-weight machine. During impact, the composites absorbed higher energy than the monophase material. The strength retention, in percentage, after the impact was significantly higher for the composite that presented damage tolerance for impact energy levels higher than monophase alumina. These results are discussed and fractographic analysis was used to identify the mechanisms responsible for the lower strength degradation of the composite.
Application of mass spectrometry to the characterization and quantification of food-derived bioactive peptides
(Oxford University Press, 2008-07-01) Contreras, María del Mar; López-Expósito, Iván; Hernández-Ledesma, Blanca; Ramos, Mercedes; Recio, Isidra
Biologically active peptides are of particular interest in food science and nutrition because they have been shown to play different physiological roles, including antihypertensive, opioid, antimicrobial, and immunostimulating activities. Because these peptides are generated by protein hydrolysis or fermentation, they can represent only minor constituents in a highly complex matrix and therefore, identification of biologically active peptides in food matrixes is a challenging task in food technology. In this context, mass spectrometry (MS) has developed into a necessary tool to assess quality and safety of food and, more recently, to determine the presence and behavior of functional components such as these bioactive peptides. This review highlights the existing methods based on MS to identify, characterize, and quantify food-derived biologically active peptides, taking into account the different ionization sources used for the analysis of these high-value food components. The quantitative determination of bioactive peptides in food products or biological fluids is also discussed.
Design and processing of a ceramic laminate with high toughness and strong interfaces
(Elsevier, 2009) Salvador, Bueno; Carmen, Baudín
ACE-inhibitory and antihypertensive properties of a bovine casein hydrolysate
(Elsevier Ltd., 2009-01-01) Miguel, Marta; Contreras, María del Mar; Recio, Isidra; Aleixandre, Amaya
The aim of this study was to investigate the potential angiotensin converting enzyme (ACE)-inhibitory activity and the antihypertensive effect, after a single oral administration, of a pepsin hydrolysed bovine casein (HBC) and a fraction with molecular mass lower than 3000 Da (HBC < 3000). ACE-inhibitory activity was measured by spectrophotometric assay. These products were orally administered by gastric intubation. The systolic (SBP) and the diastolic blood pressure (DBP) were measured in spontaneously hypertensive rats by the tail cuff method before administration and also 2, 4, 6, 8, and 24 h post-administration. HBC showed a potent ACE-inhibitory activity. This activity was 10 times higher in HBC < 3000. HBC and HBC < 3000 decreased the arterial blood pressure of the rats. The decrease in the SBP observed for HBC (400 mg/kg) or HBC < 3000 (200 mg/kg) was less pronounced than that caused by 50 mg/kg of captopril (antihypertensive positive control). However, the maximal decreases in DBP caused by HBC or HBC < 3000 were as high as the maximum decrease observed for captopril. The antihypertensive effect of these products was transient and reverted 24 h after the administration. HBC and HBC < 3000 exert antihypertensive effect caused by small peptides with ACE-inhibitory activity.
Novel casein-derived peptides with antihypertensive activity
(Elsevier Ltd., 2009-10) Contreras, María del Mar; Carrón, Rosalía; Montero, María José; Ramos, Mercedes; Recio, Isidra
In this study, we report novel casein-derived peptide sequences with angiotensin converting enzyme (ACE)-inhibitory activity and antihypertensive activity demonstrated in spontaneously hypertensive rats (SHR). The peptides were obtained by enzymatic hydrolysis of total isoelectric casein with pepsin. To identify ACE-inhibitory peptides, the casein hydrolysate was fractionated by semi-preparative high performance liquid chromatography, and 44 (CN) peptides contained in the active fractions were sequenced by using an ion trap mass spectrometer. Among the identified peptides, three sequences, that corresponded to αs1-CN f(90–94) (RYLGY), αs1-CN f(143–149) (AYFYPEL), and αS2-CN f(89–95) (YQKFPQY), showed IC50 values as low as 0.71 μm, 6.58 μm, and 20.08 μm, respectively. These three peptides also exerted antihypertensive activity when they were orally administered to SHR at a dose of 5 mg kg−1 of body weight. The activity of peptides RYLGY and AYFYPEL in SHR was similar to that found for tripeptide VPP when orally administered at the same dose.
Stability to gastrointestinal enzymes and structure–activity relationship of β-casein-peptides with antihypertensive properties
(Elsevier Inc., 2009-10) Quirós, Ana; Contreras-Gámez, María Mar; Ramos-González, Mercedes; Amigo, Lourdes; Recio, Isidra
Physiological digestion plays a key role in the formation and degradation of angiotensin-converting enzyme (ACE)-inhibitory peptides. In this study, we evaluated the impact of a simulated gastrointestinal digestion on the stability of eight peptides previously identified in fermented milk with antihypertensive activity. Two of these identified peptides with sequences LHLPLP and LVYPFPGPIPNSLPQNIPP, possess ACE-inhibitory activity in vitro and antihypertensive activity in vivo. The results showed that LHLPLP was resistant to digestive enzymes. In contrast, LVYPFPGPIPNSLPQNIPP was totally hydrolyzed and its activity decreased after incubation with pepsin and a pancreatic extract. The peptide LHLPLP was incubated with ACE and was found to be a true inhibitor of the enzyme and to exhibit a competitive inhibitor pattern. A structure–activity relationship study of this peptide was carried out by synthesizing several modified peptides related to the sequence LHLPLP. The substitution of amino acid Leu in the penultimate position by Gly improved the ACE-inhibitory activity twofold and the substitution of Pro at C-terminal position by Arg increased the activity twofold, with an IC50 of LHLPLR as low as 1.8 μM.
Processing of alumina-coated tetragonal zirconia materials and their response to sliding wear
(Elsevier, 2010) Bueno, Salvador; Ferrari, Begoña; Melandri, Cesare; de-Portu, Goffredo; Baudín, Carmen
Alumina-coated tetragonal zirconia stabilised with 3 mol% of Y2O3 (YTZP) specimens (30 mm × 30 mm × 6 mm) have been obtained by dipping of pre-sintered YTZP compacts in alumina suspensions and subsequent sintering. The coated specimens present hardness values and a wear resistance similar to those of reference dense alumina specimens and significantly higher than those of the YTZP substrates. The optimisation of the processing parameters is described. First, YTZP compacts with different open porosity levels were fabricated by colloidal filtration and subsequent thermal treatment at temperatures ranging from 1100 to 1400 °C. Coated compacts were obtained by dipping the porous ones in alumina suspensions prepared in ethanol with two different solid loadings: 3 and 10 vol.%, during immersion times up to 40 min. Sintering (1500 °C–2 h) of the coated compacts was performed and microstructural analysis allowed the selection of the optimum porosity levels for the YTZP substrates and dipping conditions. For the optimised conditions, YTZP plates (30 mm × 30 mm × 6 mm) were coated and the thermal treatment to reach densification of the substrate and the coating was optimised. Relatively thick coatings (≅200 μm) were obtained. Hardness and wear resistance were evaluated for sintered monolithic and coated YTZP compacts and an alumina reference material and the wear damage of the tested specimens was analysed.
Milk versus caseinophosphopeptides added to fruit beverage: Resistance and release from simulated gastrointestinal digestion
(Elsevier Inc., 2010-04) García-Nebot, María José; Alegría, Amparo; Barberá, Reyes; Contreras, María del Mar; Recio, Isidra
The influence of simulated gastrointestinal digestion on caseinophosphopeptides (CPPs) formation in milk-based fruit beverage was evaluated, together with resistance of a pool of CPPs added to fruit beverage. In milk-based fruit beverage, four CPPs were identified that can be justified by their presence in raw milk or due to processing. When it was subjected to simulated gastrointestinal digestion, 10 CPPs were identified, and only 1 presented the cluster (SpSpSpEE) (3 phosphoseryl group followed by 2 glutamic acid residues), which corresponded to αs2-CN(1–19)4P. CPPs added to fruit beverage are resistant to simulated gastrointestinal digestion, and 16 CPPs were identified originating from the fragmentation of added CPPs, and with a greater presence of the cluster compared with CPPs originating from milk-based fruit beverage. This could justify the use of CPPs as functional ingredients, and offer a good alternative to milk-based fruit beverage for improving mineral bioavailability.
Monitoring the large scale production of antihypertensive peptides RYLGY and AYFYPEL by HPLC-MS
(Springer Nature, 2010-04-01) Contreras-Gámez, María Mar; Gómez-Sala, Beatriz; Martín-Álvarez, Pedro Jesús; Amigo, Lourdes; Ramos-González, Mercedes; Recio, Isidra
This work reports the quantitative analysis of two novel antihypertensive peptides αs1-CN f(90-94), with sequence RYLGY, and αs1-CN f(143-149), with sequence AYFYPEL, by high-performance liquid chromatography–mass spectrometry in food-grade hydrolysates of milk proteins. The method was validated and showed sufficient specificity, reproducibility, linearity and recovery. Linear calibrations of the molecular ions m/z 671.2 and 902.3 were selected for the determination of the peptides RYLGY and AYFYPEL, respectively, and showed good statistical results (R 2 ≥ 0.995 and with no significant lack-of-fit). The simplicity of RP-HPLC-MS method allowed the automated quantification of both antihypertensive peptides without any sample pretreatment. The application of this method permitted the evaluation of some hydrolysis variables, i.e., substrate, temperature, hydrolysis time or enzyme/substrate ratio, on the formation of antihypertensive peptides. The quantitative analysis of RYLGY and AYFYPEL showed that ultrafiltration was not effective to improve the content in active peptides, containing the hydrolysates and their respective permeates similar peptide amounts.
Acute and repeated dose (4 weeks) oral toxicity studies of two antihypertensive peptides, RYLGY and AYFYPEL, that correspond to fragments (90–94) and (143–149) from αs1-casein
(Elsevier Ltd., 2010-07) Anadón, Arturo; Martínez-Caballero, María Aranzazu; Ares, Irma; Ramos-Alonso, Eva; Martínez-Larrañaga, María Rosa; Contreras-Gámez, María Mar; Ramos-González, Mercedes; Recio, Isidra
The Lowpept® is a powdered casein hydrolysate containing the antihypertensive peptides RYLGY and AYFYPEL, two sequences that correspond to αs1-casein f (90–94) (RYLGY) and αs1-casein f (143–149) (AYFYPEL). To support the safety, Lowpept® has been examined in an acute and in a 4-week repeated dose oral toxicity studies in rats. Powdered casein hydrolysate administered in a single oral gavage dose of 2000 mg/kg resulted in no adverse events or mortality. Also, casein hydrolysate administered as a daily dose of 1000 mg/kg for 4 weeks by gavage resulted in no adverse events or mortality. No evidence or treatment-related toxicity was detected during both studies. Data analysis of body weight gain, food consumption, clinical observations, blood biochemical, haematology, organ weight ratios and histopathological findings did not show significant differences between control and treated groups. It is concluded that the casein hydrolysate containing the peptides RYLGY and AYFYPEL orally administered to rats was safe and that not treatment-related toxicity was detected even at the highest doses investigated in both acute (2000 mg/kg of body weight) and repeated dose (4 weeks) oral (1000 mg/kg of body weight) toxicity studies.
Improved wear behaviour of alumina-aluminium titanate laminates with low residual stresses and large grained interfaces
(Elsevier, 2011) Bueno, Salvador; Micele, Lorenzo; Melandri, Cesare; Baudín, Carmen; de-Portu, Goffredo
The wear behaviour of a monolithic alumina and an alumina–aluminium titanate laminated structure was studied. The laminate, containing surface ﬁne grained alumina layers and internal composite layers with 10 vol.% of aluminium titanate, showed relatively low (∼=20 MPa) compressive residual stresses at the surface. Interfaces between layers were constituted by large alumina grains (up to =50 m) that promoted toughening due to crack deﬂection and branching. Wear tests were performed on square specimens (30 mm × 30 mm × 6 mm) using the pin-on-disc method. The laminates showed higher wear resistance than the monolithic alumina. The analysis of the results together with SEM-EDX observations was performed to identify possible wear mechanisms. The wear resistance improvements are discussed in terms of the residual stresses in the laminate and the properties provided by the special microstructure of the interfaces.
Production of antioxidant hydrolyzates from a whey protein concentrate with thermolysin: Optimization by response surface methodology
(Elsevier Ltd., 2011-01) Contreras-Gámez, María Mar; Hernández-Ledesma, Blanca; Amigo, Lourdes; Martín-Álvarez, Pedro Jesús; Recio, Isidra
Whey protein concentrate (WPC) enriched in β-lactoglobulin (β-Lg) was hydrolyzed using Corolase PP® and thermolysin to produce hydrolyzates with antioxidant activity. The optimization of the main experimental variables involved in the process, such as type of enzyme, and hydrolysis conditions, concretely enzyme to substrate ratio, time and temperature, were evaluated using response surface methodology. A central composite circumscribed (CCC) design was employed to study the effect of the experimental variables on the antioxidant activity determined by radical scavenging potency. The parameters of the model were estimated by multiple linear regression, and the highest radical scavenging activity (2.57 μmol Trolox/mg protein) was found in WPC hydrolyzed with thermolysin after 8 h at 80 °C and an enzyme/substrate ratio of 0.10 (w/w). Nineteen β-Lg derived peptides were identified by RP-HPLC-MS/MS in this hydrolyzate. Of special interest are peptides LQKW f(58–61) and LDTDYKK f(95–101), which amino acid composition makes them potential contributors on the radical scavenging activity detected.
Development of a process for the production of L-aminoacids concentrates from microalgae by enzymatic hydrolysis
(Elsevier, 2012-02-28) Romero-García, Juan M.; Acién, Francisco G.; Fernández-Sevilla, José M.
A process for the production of L-amino-acids concentrates from microalgae biomass by enzymatic hydrolysis has been developed. The process includes pre-treatment for cell-disruption, enzymatic hydro- lysis and ﬁnal separation by centrifugation. Thermal and mechanical cell-disruption methods have been tested, selecting mechanical disruption using bead milling for 30 min. The enzymatic hydrolysis was done using the commercial enzymes Alcalase and Flavourzyme. Maximum hydrolysis was obtained for biomass concentrations under 270 g/l and previous additional treatment with Viscozyme, reaching a 42% hydrolysis. Repeated reaction steps increased the hydrolysis from 42% (4 h) with a single step to 59% (8 h) after two successive steps. Further increase of the number of steps had a meagre impact on the global yield. The process widens the portfolio of products that can be obtained from microalgae bio- mass and is a new possibility to enhance the economic viability of microalgae-based biofuels production processes.
Filtered Smith Predictor to control pH during enzymatic hydrolysis of microalgae to produce L-aminoacids concentrates
(Elsevier, 2012-07-23) Romero-García, Juan M.; Guzmán, José L.; Moreno, José C.; Acién, Francisco G.; Fernández-Sevilla, José M.
The main step of the production of L-aminoacids concentrates from microalgae is the enzymatic hydrolysis. This process has to be done at the optimum temperature and pH of the enzyme in order to obtain the maximum yield. In order to keep a constant pH, NaOH (1 M) or H2SO4 (1 M) are used, depending on the reaction step. When working with pH it is not possible to use the governing equations due to the complexity of the enzymatic hydrolysis. In this work, the modelling of pH is experimentally performed on a laboratory scale plant. Since the obtained model presents delay and uncertainty in the parameters, a Filtered Smith Predictor is proposed as control strategy. This control scheme has been tested in the real system. The Filtered Smith Predictor has reduced the Integral Absolute Error and the time for the solution addition in more than 25% and it has increased 5% the production of L-aminoacids compared to an on-off control, which is the controller most used in these processes.
Bioreﬁnery based on olive biomass. State of the art and future trends
(Elsevier, 2014-03-25) Romero-García, Juan Miguel; Niño, Luis; Martínez-Patiño, José Carlos; Álvarez-Vaquerizo, Cristina; Castro-Galiano, Eulogio; Negro, María José
With currently more than nine million hectares, olive tree cultivation has spread worldwide, table olives and olive oil as the main products. Moreover, a number of by-products and residues derived from both tree cultivation and the process of industrial olive oil production, most having no practical applications, are obtained yearly. This paper reviews the research regarding these by-products, namely biomass from olive tree pruning, olive stones, olive pomace and wastewaters obtained from the process of olive oil production. Furthermore, a wide range of compounds has been identified and can be produced using a broad definition of the term biorefinery based on olive tree biomass. As an example, this paper reviews ethanol production as one of the main proposed applications, as well as research on other value-added products. Finally, this paper also assesses recent technological advances, future perspectives and challenges in each stage of the process.

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