DIQAM-Artículos
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Ítem Acorn gasification char valorisation in the manufacture of alkali activated materials(Elsevier, 2023-09-30) Gómez-Casero, Miguel Ángel; Calado, Luís; Romano, Pedro; Eliche-Quesada, DoloresThe use of biomass for energy production is becoming increasingly common. An energy source with good prospects for the future is the gasification process of biomass waste. This process is characterized by the partial oxidation of the raw material at high temperatures, which converts the raw material into a mixture of combustible gases. However, one of the problems when using biomass is the ash produced in the gasification process. This study investigates the effect of the incorporation of ash generated in the production of syngas from biomass residues from the acorn industry on the physical, mechanical and thermal performance of electric arc furnace slag (EAFS) based alkaline activated cements for industrial applications. Acorn gasification ash (AGA) after a calcination process were used to replace EAFS at different substitution ratios: 0, 25, 50, 75 and 100 wt%. The influence of the modulus of the activator (Ms = SiO2/K2O = 0.89; 1.38 and 1.84) was also studied. The specimens were evaluated for density, porosity, flexural and compressive strength, thermal conductivity, X-ray diffraction analysis, infrared spectroscopy, and microstructure development at 1, 7, 28 and 56 days of curing. The results showed that the inclusion of up to 50 wt% AGA gives rise to cements with similar or higher compressive strength than the control cement containing only EAFS. The optimum activator modulus depends on the proportion of precursors used, increasing with increasing AGA content. Therefore, the activator ratio and AGA content are factors that must be considered simultaneously to achieve the optimum compressive strength. The main reaction product was C-(A)-S-H gel, and to a lesser extent K-(A)-S-H gel and C-K-(A)-S-H hybrid gel. This work suggests the use of AGA improve alkali activated metallurgical slag binders, partially substituting the conventional Portland cement as structural material.Ítem Effect of olive-pruning fibres as reinforcements of alkali-activated cements based on electric arc furnace slag and biomass bottom ash(Springer Nature, 2024-03-18) Gómez-Casero, Miguel Ángel; Sánchez-Soto, Pedro José; Castro-Galiano, Eulogio; Eliche-Quesada, DoloresIn this work, alkali-activated composites using electric arc furnace slag (50 wt%) and biomass bottom ash (50 wt%) were manufactured, adding olive-pruning fibres as reinforcement. The objective of adding fibres is to improve the flexural strength of composites, as well as to prevent the expansion of cracks as a result of shrinkage. For this reason, composites reinforced with olive-pruning fibres (0.5–2 wt%) untreated and treated with three different solutions to improve matrix–fibre adhesion were manufactured. Treatments developed over fibres were a 10 wt% Na2SiO3 solution, 3 wt% CaCl2 solution and 5 wt% NaOH solution. Mechanical properties, physical properties, thermal properties and the microstructure of composites by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were studied to demonstrate the improvement. Alkaline treatment degraded fibre surface, increasing the matrix–fibre adhesion, and as a consequence, flexural strength increased up to 20% at 90 days of curing. Optimal results were obtained with composites reinforced with 1 wt% of olive-pruning fibre treated by a 10 wt% Na2SiO3 solution. Higher quantity of olive-pruning fibre leads to local agglomeration, which weakens the matrix–fibre adhesion. The effect on the compressive strength is less evident, since the addition of fibres produces an admissible decrease (between 0 and 9% using 0.5 or 1 wt% of fibres), except in composites that use olive pruning treated with 10 wt% Na2SiO3 solution, where values remain stable, similar or better to control paste. A greater ductility of the matrix in all composites was observed. Furthermore, the alkali-activated cement matrix was bonded to olive-pruning fibre better than untreated fibre, as it is shown in SEM images. Thus, the results showed that olive-pruning fibres could be used as reinforcement in the manufacturing of alkali-activated materials when they are treated with alkali solutions.Ítem Physical, mechanical and thermal properties of metakaolin-fly ash geopolymers(Elsevier, 2022-02-16) Gómez-Casero, Miguel Ángel; de-Dios-Arana, Cristina; Bueno-Rodríguez, Juan Salvador; Pérez-Villarejo, Luis; Eliche-Quesada, DoloresDue to the large coal fly ash (FA) production and its obvious environmental impact, alternative uses of this by-product must be researched. A considerable effort is being made worldwide on research concerning the reuse of FA as a source of alternative raw materials to produce new binder materials. One of the most promising building materials are geopolymers or alkali-activated materials (AAM). In this study, FA (25–75 wt %) was used to evaluate the potential of using this waste as a source of aluminosilicates for the synthesis of geopolymers to replace metakaolin (MK) as precursor. MK and FA geopolymers were also synthesized as a control. Sodium hydroxide and sodium silicate were used as alkaline-activator mix (Na2SiO3/NaOH ratio: 0.92). The geopolymers synthesized were characterized by Fourier Transform Infrared Spectroscopy (FTIR) X-ray diffraction (XRD) and Scanning Electron Microscopy-Energy Dispersive X-ray spectroscopy (SEM-EDS). The results indicate that control geopolymers, MK and FA geopolymers have similar mechanical and thermal properties. However, the MK-FA blended geopolymers have slightly lower compressive strengths and lower thermal conductivity. The decrease in the properties of the FA and MK-FA blended geopolymers may be due to the high solid/liquid ratio used, since the spherical particles of the FA require less liquid due to their higher workability. However, the obtained geopolymers can be a satisfactory solution for the recovery of waste that results in sustainable construction materials that meet the standard to be used for loadbearing concrete masonry units with insulating properties superior to Portland cement approaching the principles of circular economy.Ítem Comparative study of alkali activated cements based on metallurgical slags, in terms of technological properties developed(Elsevier, 2022-06-23) Gómez-Casero, Miguel Ángel; Pérez-Villarejo, Luis; Sánchez-Soto, Pedro José; Eliche-Quesada, DoloresIn this work, an investigation on the use of two slags from different origins (electric arc furnace slag (EAFS) and copper slag (CS)) as raw materials in the manufacture of alkali-activated cements has been carried out. A comparison of the different mechanical properties developed by the alkaline activation of each raw material has been studied. Combination of 35 wt% potassium hydroxide (KOH) solution with different concentration (5, 8, 12 and 15 M) and 65 wt% potassium silicate (K2SiO3) solution was used as activating solution to manufacture alkali activated cements. The pastes were cured 24 h in a climatic chamber at 20 °C at 90% of relative humidity, subsequently demoulded and cured at same condition during 1, 7, 28 and 90 days. Alkali activated materials have been characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The physical properties: bulk density, water absorption and apparent porosity, mechanical properties, flexural strength and compressive strength and thermal properties: thermal conductivity have been determined. The results indicate that two types of slags studied are a suitable source of aluminosilicates that can be activated for the manufacture of alkali-activated materials. These precursors are capable of developing high values of flexural and compressive strength and low values of thermal conductivity when optimal concentration of KOH was used. The optimal composition was developed when CS was utilized. Binders with CS and 12 M M ratio achieved compressive strength values up to 70 MPa.Ítem Alkaline-activated cements synthesized from spent diatomaceous earth and different industrial sludge ashes(Taylor & Francis, 2025-07-29) Felipe-Sesé, Manuel; García-Díaz , Almudena; Gómez-Casero, Miguel Ángel; Eliche-Quesada, DoloresThis study evaluates the technological properties of alkali-activated cements (AACs) produced from spent diatomaceous earth (SDE), a by-product of beer filtration, combined with 20wt.% of industrial sludge ashes. The ashes used include brewery sludge ash (BSA), oil industry sludge ash (OSA), pulp–paper sludge ash (PSA), and aluminum anodizing sludge ash (AASA). Activation was carried out using a 1:1 mixture of sodium silicate and sodium hydroxide, with curing at room temperature for 7 and 28 days. Microstructural analysis was performed using X-ray diffractometer (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The results show that the chemical composition of the sludge ashes significantly influences the mechanical performance of AACs. Calcium-rich wastes improved compressive strength, while the presence of SO3 and P2O5 reduced it due to the formation of expansive phases or secondary reactions. The best results were achieved with BSA-SDE cements, which reached compressive and flexural strengths of 30.0 and 6.5MPa, respectively.Ítem Alkaline activated cements obtained from ferrous and non-ferrous slags. Electric arc furnace slag, ladle furnace slag, copper slag and silico-manganese slag(Elsevier, 2024-03) Gómez-Casero , Miguel Ángel; Bueno, Salvador; Castro-Galiano, Eulogio; Eliche-Quesada, DoloresFerrous slag: electric arc furnace slag (EAFS) and ladle furnace slag (LFS); and non-ferrous slag: copper slag (CS) and silicon-manganese slag (SiMnS) have been used as precursors for alkali activated cements (AACs). The objective of the study was to evaluate the effect of the silica modulus (Ms = SiO2/K2O) (0.5–1.8) of the potassium silicate/potassium hydroxide solution on the microstructure and technological properties of AACs using individual slags. The results obtained indicate that under the activation conditions used, CS and EAFS are more reactive slags, giving rise to AACs with optimum flexural and compressive strengths of 7.5 and 51.5 MPa and 5.7 and 30.5 MPa for a Ms = 1.4, respectively. While the SiMnS and LFS are less reactive resulting in AACs with flexural and compressive strengths of 3.2 and 11.6 MPa at Ms = 1.4 for SiMnS and 1.1 MPa and 4.6 MPa at Ms = 0.9 for LFS. In all AACs, the development of the alkaline activation reaction is confirmed due to the presence of gel, of different nature and quantity depending on the precursor used. The lower mechanical properties of the AACs using SiMnS and LFS as precursor may also be due to the presence of microcracks. Therefore, this study confirms that ferrous and non-ferrous slags can be used as precursors of AACs, with the type of precursor and the modulus of the activating solution influencing mechanical properties. AACs using CS and EAFS can be used in structural applications, while those using SiMnS and LFS can be used in non-structural applications in civil engineering.Ítem Investigation of waste clay brick (chamotte) addition and activator modulus in the properties of alkaline activation cements based on construction and demolition waste(Elsevier, 2024-05-01) García-Díaz, Almudena; Delgado-Plana, Pedro; Bueno, Salvador; Eliche-Quesada, DoloresThe use of construction and demolition waste (CDW) as a raw material for the manufacture of alkali-activated cements (AACs) is a promising and sustainable way to recover construction waste. CDW mainly consists of mineral residues such as concrete and ceramic waste. In this study, CDW with a high fraction of concrete waste is used, so the enrichment effect of the waste in the ceramic fraction is studied. For this purpose, different proportions of chamotte (CHM) have been incorporated (0–40 wt%). The CDW precursor or CDW-CHM precursors have been activated using 8 M sodium hydroxide and sodium silicate solution, using an activator modulus (mol SiO2/mol Na2O = Ms = 1.0) and the specimens were cured at room temperature. The liquid/binder ratio was 0.45 for all the pastes manufactured. The results indicate that the progressive enrichment of the ceramic fraction or the incorporation of CHM results in alkaline activated cements (AACs) with similar physical properties such as bulk density, water absorption and total porosity, but with improved mechanical properties. The incorporation of 40 wt% CHM results in optimum compressive strengths with values of 29.7 and 41.2 MPa after 28 and 56 days of curing respectively, higher than those obtained for the control specimens containing only CDW 15.2 MPa and 30.65 MPa respectively. Subsequently, the impact of the silicate modulus of the alkaline activator (Ms = 0.5; 1.0 and 2.0) on the performance of the AACs was evaluated in the control cement and in the optimum cement incorporating 40 wt% CHM. The mechanical performance of the AACs improves substantially with increasing activator modulus up to a certain threshold Ms = 1.0, but finally decreases slightly with Ms = 2.0. Therefore, this study demonstrates the possibility of valorising wastes from the construction sector through their use as precursors in the manufacture of environmentally friendly alkaline activated cements with macroscopic performances that improve with the content of the ceramic fraction (CHM).Ítem Delignification of Olive Tree Pruning Using a Ternary EutecticSolvent for Enhanced Saccharification and Isolation of a UniqueLignin Fraction(ACS Publications, 2024-09-30) Gómez-Cruz , Irene; Nalin, Seixas; Labidi, Jalel; Castro, Eulogio; Silvestre, Armando J.D.; da Costa Lopes, AndréThis work aimed at exploring the potentialities of eutectic solvents (ES) in the fractionation of olive tree pruning (OTP) biomass within a biorefinery framework, targeting efficient separation of cellulose fibers and lignin and simultaneously producing high-quality fractions for further processing and application. In this sense, delignification performances of cholinium chloride:ethylene glycol, ChCl:EG (1:9) and cholinium chloride:p-toluenesulfonic acid:ethylene glycol, ChCl:pTSA:EG (1:1:9) as binary and ternary mixtures, respectively, were first evaluated. ChCl:EG demonstrated low efficacy for biomass delignification, while the highest lignin extraction (62.7%) was achieved with ChCl:pTSA:EG at 80 °C and 4 h. At the same conditions, the cellulose content (62.5%) of the resulting solid fraction increased almost three-fold compared to that of the raw OTP (22.3%), using ChCl:pTSA:EG. This ternary ES enabled the OTP matrix breakdown, which, combined with lignin extraction, enhanced the enzymatic hydrolysis of the cellulose-rich fraction to a maximum saccharification yield of 81.8%. The sample exhibited an impressive aliphatic OH group content of 5.2 mmol·g–1 lignin, one of the highest values among the state-of-the-art. The resulting phenomenon is explained by the ethylene glycol grafting onto the lignin structure (aliphatic region), as demonstrated by 31P and HSQC NMR, giving chemical functionality to the isolated lignin fraction. Finally, up to 90% of the initial mass of ChCl:pTSA:EG was recovered through the adsorption of impurities. NMR data validated the high purity and the same molar ratio (1:1:9) of recovered ES, two important outcomes to ensure a sustainable reutilization of this solvent.Ítem A biorefinery approach to obtain antioxidants, lignin and sugars from exhausted olive pomace(Elsevier, 2021-01-30) Gómez-Cruz , Irene; Contreras Gámez, María del Mar; Romero , Inmaculada; Castro , EulogioExhausted olive pomace (EOP) is the main residue of the pomace olive oil extracting industry. In this work, EOP was fractionated into valuable components for valorisation: an aqueous extract rich in hydroxytyrosol and mannitol, lignins with antioxidant properties and fermentable sugars. EOP was first subjected to water extraction at 85 °C for 90 min. Several pretreatments based on liquid hot water and organosolv with 50% or 60% ethanol (catalysed and uncatalysed with 1% sulfuric acid) were then evaluated in terms of delignification ability and efficiency for enzymatic hydrolysis of the pretreated solids. Once the best conditions had been selected (50 % ethanol-1% sulfuric acid at 130 °C for 60 min), an organosolv lignin (OL) with antioxidant properties was obtained through acid precipitation of the pretreatment liquor. This was compared to the enzymatic hydrolysis lignin obtained in the subsequent step and to the lignins purified by acid hydrolysis. OL showed a higher total phenolic content and antioxidant activity than the rest of the lignin samples. Chemical differences were also observed that could explain the results.Ítem Optimization of Microwave-Assisted Water Extraction to Obtain High Value-Added Compounds from Exhausted Olive Pomace in a Biorefinery Context(MDPI, 2022-07-06) Gómez-Cruz , Irene; Contreras Gámez, María del Mar; Romero, Inmaculada; Castro , EulogioMicrowave-assisted water extraction (MAWE) was evaluated to obtain the valuable bioactive compounds hydroxytyrosol and mannitol from exhausted olive pomace (EOP). The influence of the operational parameters solid loading (3–15%, w/v), temperature (40–100 °C), and extraction time (4–40 min) was studied using an experimental design. The optimized conditions maximizing their joint extraction were 12% w/v solid loading, 100 °C temperature, and 16 min. It was possible to solubilize 5.87 mg of hydroxytyrosol/g EOP and 46.70 mg mannitol/g EOP. The extracts were also further characterized by liquid chromatography–mass spectrometry, which detected other hydroxytyrosol derivatives such as oleacein, verbascoside, and oleuropein. Moreover, the applied MAWE conditions promoted the co-extraction of proteinaceus material, which was also evaluated. In order to carry out an integral valorization of this waste, the extracted EOP solid was further evaluated chemically and microscopically before recovering the bioactive triterpenes. In particular, maslinic acid and oleanolic acid were obtained, 9.54 mg/g extracted solid and 3.60 mg/g extracted solid, respectively. Overall, MAWE can be applied as a first stage in the fractionation of EOP to support its valorization in a biorefinery framework.Ítem Combined Extraction and Ethanol Organosolv Fractionation of Exhausted Olive Pomace for Bioactive Compounds(Wiley Online Library, 2022-01-25) Gómez-Cruz , Irene; Romero, Inmaculada; Contreras Gámez , María del Mar; Labidi, Jalel; Hernández-Ramos, Fabio; Roseiro, Luisa B.; Duarte, Luis C.; Castro , Eulogio; Carvalheiro, FlorbelaThe olive pomace oil extracting industry generates large amounts of exhausted olive pomace (EOP), a lignocellulosic waste that needs to be managed according to sustainable criteria. The aim of this work is to devise an integrated strategy to valorize EOP by applying two-step extraction, and to evaluate the effect of an ethanol organosolv pretreatment on the delignification and enzymatic hydrolysis of the extracted EOP. Once the extraction and organosolv pretreatment conditions are selected, solubilized lignin is recovered from the pretreatment liquor using different methods. In addition to those organosolv lignin samples, a lignin-rich solid is obtained after enzymatic saccharification of the pretreated solid. All the lignin samples are fully characterized aiming at further valorization. The selected two-step aqueous extraction (85 °C, 90 min, 10% biomass) removes 89% of the extractives content in raw EOP and achieves the full recovery of phenols and mannitol content in that fraction, 4.7 mg gallic acid equivalents per g EOP and 4.5 mg g−1 EOP, respectively. The organosolv pretreatment (50% ethanol catalyzed with 1% H2SO4, 140 °C, 60 min, 15% biomass) results in a delignified solid with 81% of enzymatic digestibility and a high purity organosolv lignin (>71%), rich in guaiacyl units.Ítem Sequential Extraction of Hydroxytyrosol, Mannitol and Triterpenic Acids Using a Green Optimized Procedure Based on Ultrasound(MDPI, 2021-11-07) Gómez-Cruz , Irene; Contreras Gámez , María del Mar; Romero, Inmaculada; Castro, EulogioOlive-derived biomasses contain bioactive compounds with health promoting effects as well as antioxidant and sweet-tasting properties. However, their sequential extraction has not been attained. In the present study, firstly antioxidants and mannitol were extracted from exhausted olive pomace (EOP) by an eco-friendly method, ultrasound-assisted water extraction (UAWE). The amplitude (20–80%), extraction time (2–18 min) and solid loading (2–15%, w/v) were evaluated according to a Box–Behnken experimental design. Using the response surface methodology, the optimal conditions for extraction were obtained: 80% amplitude, 11.5% solid loading and 16 min. It enabled the multi-response optimization of the total phenolic content (TPC) (40.04 mg/g EOP), hydroxytyrosol content (6.42 mg/g EOP), mannitol content (50.92 mg/g EOP) and antioxidant activity (ferric reducing power or FRAP, 50.95 mg/g EOP; ABTS, 100.64 mg/g EOP). Moreover, the phenolic profile of the extracts was determined by liquid chromatography-UV and mass spectrometry, identifying hydroxytyrosol as the main phenolic compound and other minor derivatives could be characterized. Scanning electron microscopy was used to analyze the morphological changes produced in the cellular structure of EOP after UAWE. In addition, the chemical composition of the extracted EOP solid was characterized for further valorization. Then, a second extraction step was performed in order to extract bioactive triterpenes from the latter solid. The triterpenes content in the extract was determined and the effect of the previous UAWE step on the triterpenes extraction was evaluated. In this case, the use of ultrasound enhanced the extraction of maslinic acid and oleanolic acid from pelletized EOP with no milling requirement. Overall, UAWE can be applied to obtain antioxidant compounds and mannitol as first extraction step from pelletized EOP while supporting the subsequent recovery of triterpenic acids.Ítem Hepatopreventive properties of hydroxytyrosol and mannitol-rich extracts obtained from exhausted olive pomace using green extraction methods(Royal Society of Chemistry, 2022-12-25) Contreras, María del Mar; Gómez -Cruz, Irene; Feriani, Anouar; Alwasel, Saleh; Harrath, Abdel Halim; Romero-Pulido, Inmaculada; Castro-Galiano, Eulogio; Tlili, NizarExhausted olive pomace (EOP) is produced in olive-pomace oil extractors as a by-product. However, the obtention of bioactive compounds from EOP can reinsert it into the economy as a new bioresource before applying other exploitation ways. The objective of the present study was to investigate the phytochemical differences between aqueous and aqueous acetonic extracts from EOP (AE-EOP and AAE-EOP, respectively) obtained by hydrothermal and ultrasound-assisted extraction, respectively. The in vitro antioxidant activities and the in vivo hepatopreventive potential were evaluated. Using RP-HPLC–ESI–QTOF– MS, the chemical profile revealed that AE-EOP and AAE-EOP showed similar qualitative profiles, with some quantitative differences. Hydroxytyrosol and mannitol were the major compounds of the extracts. The investigation of antioxidant properties in vitro highlighted that AE-EOP was slightly more efficient in scavenging DPPH, ABTS, superoxide, and hydrogen peroxide radicals, when compared to AAE-EOP. Additionally, AE-EOP and AAE-EOP showed dose-dependent suppressive effects on pancreatic lipase activity. In vivo studies showed that AE-EOP and AAE-EOP presented interesting hepatopreventive capacities against CCl4 induced liver injury, as evidenced by (i) the preventive effects against DNA damage, (ii) the normalised hepatic biomarker parameters (ALT, AST, GGT, and LDH) and (iii) the normalised lipid profile (LDL-C, TC, TG, and HDL-C) through diminishing their levels, (iv) which was supported by Oil Red O analysis. Furthermore, AE-EOP and AAE-EOP reduced the oxidative stress in liver tissue by inhibiting lipid peroxidation together with the enhancement of the hepatic antioxidant activities (CAT, SOD and GPx) and GSH content. Additionally, AE-EOP and AAE-EOP exhibited an antifibrotic effect, which was clearly demonstrated by the histopathological examination using Picrosirius red staining. The obtained results support the use of EOP extracts in industries without further purification as antioxidants and against free radical induced damage.Ítem Ephedra alata Subsp. Alenda as a novel source of bioactive phytochemicals: Characterization based on the mass spectrometry and profiling of antioxidant and anti-Inflammatory properties.(MDPI, 2023-01-23) Mufti, Afoua; Contreras, María del Mar; Gómez-Cruz , Irene; Alshamrani, Abdullah; Nahdi, Saber; Mansour, Lamjed; Alwasel, Salah; Halim Harrath, Abdel; Tlili, NizarThe aim of the present study was to examine, for the first time, the phytochemical content of Ephedra alata pulp extract (EAP) and explore its antioxidant and anti-inflammatory capacities. High-performance liquid chromatography-electrospray ionization-quadrupole-time-of-flight mass spectrometry (HPLC-ESI-QTOF/MS) was used for phytochemical analysis and three in vitro antioxidant assays together with three in vitro anti-inflammatory tests were used for the assessment of biological activity. The HPLC-ESI-QTOF/MS analysis revealed the presence of 42 metabolites, including flavonoids, sphingolipides, fatty acids, ephedrine derivatives, and amino acid derivatives. In vitro findings revealed that EAP has interesting 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide, and ferrous ion chelating capacities (IC50 values were 0.57 mg/mL, 0.55 mg/mL, and 0.51 mg/mL for DPPH, superoxide radical, and ferrous ion, respectively). Furthermore, EAP showed a noticeable anti-inflammatory ability by inhibiting the two cyclooxygenase isoforms, COX-1 and COX-2 (IC50 of 59.1 and 58.8 µg/mL for COX-1 and COX-2, respectively), preventing protein denaturation (IC50 = 0.51 mg/mL), and protecting membrane stabilization (IC50 = 0.53 mg/mL). The results highlighted the use of Ephedra alata pulp as a potential source of natural compounds with therapeutic effects for the management of inflammatory disorders.Ítem Recovery of Bioactive Compounds from Industrial Exhausted Olive Pomace through Ultrasound-Assisted Extraction(MDPI, 2021-06-10) Gómez-Cruz , Irene; Contreras Gámez, María del Mar; Carvalheiro, Florbela; Duarte, Luis C.; Roseiro , Luisa B.; Romero , Inmaculada; Castro , EulogioExhausted olive pomace (EOP) is the main agro-industrial waste of the olive pomace extracting industries. It contains phenolic compounds and mannitol, so the extraction of these bioactive compounds should be considered as a first valorization step, especially if EOP is used as biofuel. Therefore, EOP was subjected to bath-type ultrasound-assisted extraction (UAE), and the effects of the acetone concentration (20–80%, v/v), solid load (2–15%, w/v), and extraction time (10–60 min) on the extraction of antioxidant compounds were evaluated according to a Box–Behnken experimental design. By means of the response surface methodology, the optimum conditions were obtained: 40% acetone, 8.6% solids, and 43 min. For all the extracts, the total phenolic content (TPC), flavonoid content (TFC), and antioxidant activity (DPPH, ABTS, and FRAP) were determined. With the aim of shortening the extraction time, a two-level factorial experiment design was also carried out using a probe-type UAE, keeping the solid load at 8.6% (w/v) and the acetone concentration at 40% (v/v), while the amplitude (30–70%) and the extraction time (2–12 min) were varied to maximize the aforementioned parameters. Finally, a maximum of phenolic compounds was reached (45.41 mg GAE/g EOP) at 12 min and 70% amplitude. It was comparable to that value obtained in the ultrasonic bath (42.05 mg GAE/g EOP), but, remarkably, the extraction time was shortened, which translates into lower costs at industrial scale. Moreover, the bioactive compound hydroxytyrosol was found to be the major phenolic compound in the extract, i.e., 5.16 mg/g EOP (bath-type UAE) and 4.96 mg/g EOP (probe-type UAE). Other minor phenolic compounds could be detected by capillary zone electrophoresis and liquid-chromatography–mass spectrometry. The sugar alcohol mannitol, another bioactive compound, was also found in the extract, and its content was determined. Thus, the use of this technology can support the valorization of this waste to obtain bioactive compounds, including mannitol, hydroxytyrosol, and other derivatives, before being applied for other uses.Ítem Valorisation of Exhausted Olive Pomace by an Eco-Friendly Solvent Extraction Process of Natural Antioxidants(MDPI, 2020-10-17) Gómez-Cruz , Irene; Cara, Cristóbal; Romero , Inmaculada; Castro , Eulogio; Gullón , BeatrizExhausted olive pomace (EOP) is the waste generated from the drying and subsequent extraction of residual oil from the olive pomace. In this work, the effect of different aqueous solvents on the recovery of antioxidant compounds from this lignocellulosic biomass was assessed. Water extraction was selected as the best option for recovering bioactive compounds from EOP, and the influence of the main operational parameters involved in the extraction was evaluated by response surface methodology. Aqueous extraction of EOP under optimised conditions (10% solids, 85 °C, and 90 min) yielded an extract with concentrations (per g EOP) of phenolic compounds and flavonoids of 44.5 mg gallic acid equivalent and 114.9 mg rutin equivalent, respectively. Hydroxytyrosol was identified as the major phenolic compound in EOP aqueous extracts. Moreover, these extracts showed high antioxidant activity, as well as moderate bactericidal action against some food-borne pathogens. In general, these results indicate the great potential of EOP as a source of bioactive compounds, with potential uses in several industrial applications.Ítem Lower Energy-Demanding Extraction of Bioactive Triterpene Acids by Microwave as the First Step towards Biorefining Residual Olive Skin(MDPI, 2024-10-09) Gómez-Cruz , Irene; Contreras Gámez , María del Mar; Romero, Inmaculada; Castro , EulogioIn the olive oil industry, a pit fraction is collected from olive pomace and split into a clean pit fraction and a residual olive skin-rich fraction, which does not an industrial application. Therefore, in this work, microwave-assisted extraction (MAE) was applied to obtain high-value triterpene acids (maslinic acid and oleanolic acid) from this biomass using the renewable solvent ethanol. The response surface methodology was used to gain a deeper understanding of how the solvent (ethanol–water, 50–100% v/v), time (4–30 min), and temperature (50–120 °C) affect the extraction performance, as well as the energy required for the process. The effect of milling was also studied and the solid-to-liquid ratio was also evaluated, and overall, a good compromise was found at 10% (w/v) using the raw sample (unmilled biomass). The optimised conditions were applied to residual olive skin sourced from various industries, yielding up to 5.1 g/100 g and 2.2 g/100 g dry biomass for maslinic acid and oleanolic acid, respectively. In conclusion, the residual olive skin is a promising natural source of these triterpene acids, which can be extracted using MAE, releasing extracted solids rich in polymeric carbohydrates and lignin that can be valorised under a holistic biorefinery process.Ítem Olive Pomace-Derived Biomasses Fractionation through a Two-Step Extraction Based on the Use of Ultrasounds: Chemical Characteristics(MDPI, 2021-01-07) Contreras Gámez, María del Mar; Gómez-Cruz , Irene; Romero, Inmaculada; Castro, EulogioOlive-derived biomass is not only a renewable bioenergy resource but also it can be a source of bioproducts, including antioxidants. In this study, the antioxidant composition of extracted olive pomace (EOP) and a new byproduct, the residual fraction from olive pit cleaning (RFOPC or residual pulp) was characterized and compared to olive leafy biomass, which have been extensively studied as a source of antioxidants and other bioactive compounds with pharmacological properties. The chemical characterization showed that these byproducts contain a high amount of extractives; in the case of EOP, it was even higher (52.9%) than in olive leaves (OL) and olive mill leaves (OML) (35.8–45.1%). Then, ultrasound-assisted extraction (UAE) was applied to recover antioxidants from the extractive fraction of these biomasses. The solubilization of antioxidants was much higher for EOP, correlating well with the extractives content and the total extraction yield. Accordingly, this also affected the phenolic richness of the extracts and the differences between all biomasses were diminished. In any case, the phenolic profile and the hydroxytyrosol cluster were different. While OL, OML, and EOP contained mainly hydroxytyrosol derivatives and flavones, RFOPC presented novel trilignols. Other compounds were also characterized, including secoiridoids, hydroxylated fatty acids, triterpenoids, among others, depending on the bioresource. Moreover, after the UAE extraction step, alkaline extraction was applied recovering a liquid and a solid fraction. While the solid fraction could of interest for further valorization as a biofuel, the liquid fraction contained proteins, sugars, and soluble lignin, which conferred antioxidant properties to these extracts, and whose content depended on the biomass and conditions applied.Ítem Grapevine shoot extract rich in trans-resveratrol and trans-ε-viniferin: evaluation of their potential use for cardiac health(MDPI, 2023-12-02) Contreras Gámez, María del Mar; Feriani , Anouar; Gómez-Cruz , Irene; Hfaiedh, Najla; Harrath, Abdel Halim; Romero, Inmaculada; Castro , Eulogio; Tlili, NizarA grapevine shoot extract (GSE) was obtained using ultrasound-assisted extraction and characterized. The main phenolic constituents were identified as stilbenoids. Among them, trans-resveratrol and trans-ε-viniferin stood out. The GSE was administered to an isoproterenol-induced myocardial injury animal model. The extract alleviated the associated symptoms of the administration of the drug, i.e., the plasma lipid profile was improved, while the disturbed plasma ion concentration, the cardiac dysfunction markers, the DNA laddering, and the necrosis of myocardial tissue were diminished. This effect could be related to the anti-oxidative potential of GSE associated with its antioxidant properties, the increased levels of endogenous antioxidants (glutathione and enzymatic antioxidants), and the diminished lipid peroxidative markers in the heart. The results also revealed angiotensin-converting enzyme (ACE)-inhibitory activity, which indicated the potential of GSE to deal with cardiovascular disease events. This work suggests that not only trans-resveratrol has a protective role in heart function but also GSE containing this biomolecule and derivatives. Therefore, GSE has the potential to be utilized in the creation of innovative functional ingredients.Ítem Towards the Integral Valorization of Olive Pomace-Derived Biomasses through Biorefinery Strategies(Wiley Online Library, 2024-01-24) Gómez-Cruz , Irene; Contreras Gámez , María del Mar; Romero, Inmaculada; Castro , EulogioThe olive oil sector generates a high quantity of biomasses every year, especially in the Mediterranean region. Olive pomace is the main one, but depending on the extraction and subsequent processing, other derived biomass by-products are generated like pâté, exhausted olive pomace, olive stone, and residual pulp. Their sustainable valorization is crucial. Therefore, this review first conceptualizes the current situation of the olive oil sector and describes these biomasses from a qualitative and quantitative point of view. Second, information on the bioactive compounds they present, the technologies used for their extraction, and examples of applications for their extracts is provided. Third, since the extraction of bioactive compounds will generate new residual biomasses, this review takes a step forward by integrating the extraction step in biorefinery cascading schemes. It also analyzes the benefits of this integration, the contribution to a circular (bio)economy, and the achievement of sustainable development goals.