Examinando por Autor "Castro, Eulogio"

Mostrando 1 - 19 de 19

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 A.; Bueno Rodríguez, Salvador; Castro, Eulogio; Eliche Quesada, Dolores
Ferrous 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.
An integrated olive stone biorefinery based on a 1 two-step fractionation strategy
(Elsevier, 2022) Padilla-Rascón, Carmen; Carvalheiro, Florbela; Duarte, Luís C.; Roseiro, Luisa B.; Ruiz, Encarnación; Castro, Eulogio
Olive stones (OS) constitute a waste lignocellulosic material produced by the olive oil industry in great amounts, that currently is only used as a low-value energy source for industrial or domestic boilers. Having in view its full valorization, this work proposes and validates an integrated strategy aiming to obtain three different streams of sugars / lignin-derived compounds. Dilute acid hydrolysis was used to obtain a xylose-rich hydroysate that was chemically converted into furfural with a 48.7 % yield. The resulting acid-pretreated solid biomass that consisted mainly of lignin and cellulose, was subjected to a catalyzed ethanol-based organosolv delignification. Temperature, time, and sulphuric acid concentration were optimized in order to recover added-value lignin products and digestible cellulose. At the optimal conditions (190 ᵒC and 30 min), a 50 % delignification was reached, together with the highest enzymatic hydrolysis yields (190 g glucose/kg of OS). Phenolic compounds content in organosolv liquors reached 41.6 mg GAE/g OS. This extract presented an antioxidant capacity up to 10.9 mg TE/g OS. The pretreated solid fraction was used as a substrate for ethanol production by a pre-saccharification and simultaneous saccharification and fermentation process, enabling to obtain an ethanol concentration of 47 g/L, with a fermentation yield of 61.4% of the theoretical maximum. Globally, from 100 kg of OS processed according to this experimental scheme, 6.9 kg of furfural, 6.2 kg of ethanol, 7.4 kg of lignin, and 4.2 kg of phenolics compounds can be obtained as main products, thus constituting a way of valorization of renewable material in a multiproduct biorefinery strategy.
Análisis del proceso de extracción de antioxidantes del hueso de oliva
(Universidad de Cuenca, Facultad de Ciencias Químicas (Ecuador), 2015-11-27) Hernández, Valentina; Idárraga, Ángela M.; Cerón, Ivonne X.; Romero-García, Juan M.; Castro, Eulogio; Dávila, Javier A.; Cardona, Carlos A.
Olive tree cultivation is spreading worldwide due to the beneficial effects of olive oil consumption. Olive oil production process and table olive industries are the major sources of olive stones. Currently, this by-product is used in direct combustion to produce energy as electricity or heat. However, there are other possibilities for taking full advantage of this renewable source, and its recovery would represent an economic improvement for farmers.The olive stone not only contains primarily lignocellulosic, but also it has revealed the presence of phenolic compounds with antifungal and antibacterial properties. For this reason, in this work the extraction of antioxidant compounds is proposed as a process with supercritical fluids for olive stone. These bioactive molecules can be used in the food industry, cosmetics, functional foods, and nutraceuticals additives. During the analysis of percent inhibition of DPPH method, an antioxidant capacity of 5.63 mg trolox equivalent (TE) per g dry matter was found.
Biological hydrogen and furfural production from steam-exploded vine shoots
(Elsevier, 2023) Castro, Eulogio; Rabelo, Camila A.B.S.; Padilla-Rascón, Carmen; Vidal, Alfonso M.; López-Linares, Juan Carlos; Varesse, Maria B.A.; Romero, Inmaculada
Vine shoots are an agricultural waste rich in carbohydrates that can be considered as a promising energy source alternative. The objective of this work was to propose a process strategy for the valorisation of this residual biomass, including the chemical conversion of solubilised sugars into furfural and the biological conversion of cellulosic glucose into H2. Vine shoots were subjected to steam explosion pretreatment, and its operational conditions were optimised as 190 ºC and 1.6% H2SO4 impregnated biomass. These pretreatment conditions allowed to recover 68.2% of the hemicellulose sugars and 18.2% of glucose in the prehydrolysate and 45.3% glucose by enzymatic hydrolysis. Thus, the pretreated solid obtained under optimised conditions was subjected to enzymatic hydrolysis and the slurry generated was used as a substrate by Clostridium butyricum for fermentation into biohydrogen (830.7 mL/L and a yield of 3,550 mL per 100 g of raw vine shoots) and organic acids (1,495.3 mg acetic acid/L and 1,726.8 mg butyric acid/L). Based on furfural production, the chemical conversion of xylose in the pre-hydrolysate was optimised in a microwave reactor at 202 ºC, using 0.195 M FeCl3 as a catalyst, with a furfural production of 15 g/L and 73% yield.
Biorefining for olive wastes management and efficient bioenergy production
(Elsevier, 2021) Najafi, Elham; Castro, Eulogio; Karimi, Keikhosro
The potential of olive wastes for development of a multi-product biorefinery was investigated. Different parts of olive wastes, i.e., stone, pomace, leaves, and wood, were subjected to liquid hot water, organosolv, and acid-catalyzed organosolv (ACO) pretreatments prior to bioconversion through three different scenarios. The first scenario, i.e., anaerobic digestion of substrates for biogas production, yielded 219.3 m3 biomethane per hectare of olive trees, equated to 247.4 L gasoline. The highest methane production of 103.3 m3 was attributed to liquid hot water pretreated wood and ACO increased methane yield for leaf and stone samples by 200 and 33%, respectively. The second scenario, i.e., fermentation of wastes for bioethanol production, resulted in 295.9 L bioethanol per hectare of olive trees, equivalent to 196.1 L gasoline. Organosolv pretreated wood with 82.9% production yield and 152.5 L bioethanol constitutes this plan's dominant part. The ACO pretreatment improved fermentation yield for pomace and stone samples by 49% and 53%, respectively. The third scenario, included the utilization of olive wastes in bioethanol production, anaerobic digestion of fermentation residues, and lignin separation, resulted in 295.9 L bioethanol, 137.2 m3 biomethane, and 347.1 kg lignin, equated with 521.6 L gasoline. Furthermore, the remaining oil content in pomace and stone samples was 17% and 20%, respectively, which could be used for biodiesel production. Overall, olive wastes processing through an integrated biorefinery plant with multiple products significantly improved the energy recovery of the whole plant.
Carbon-negative products to engage society in climate action: The life cycle of olive oil
(Elsevier Ltd, 2024-04-22) Galán-Martín, Ángel; Contreras, María del Mar; Castro, Eulogio
Achieving carbon neutrality and addressing the need for ongoing carbon dioxide removal to meet the climate goal requires an urgent shift towards sustainable production and consumption practices. In this context, we turn our attention to the olive oil industry, a key food industry that strives towards more environmentally sustainable initiatives. Our study explores a novel approach that integrates bioenergy with carbon capture and storage (BECCS) into olive oil production. Employing Life Cycle Assessment, we assess the potential for carbon-negative olive oil production and its broader environmental implications. Our findings demonstrate that producing carbon-negative virgin olive oil is possible by powering the olive mill processes with BECCS based on olive prunings generated at the agricultural stage (up to −0.32 kg CO2eq per 1-l bottle of virgin olive oil). However, collateral damages to acidification and eutrophication will also emerge, which can be mitigated through careful project planning tailored to local conditions. The path forward involves strategic investments, customized policies, collaboration between public and private sectors, and consumers' willingness to support carbon offset projects. Our work may contribute to unlocking the full potential of BECCS, offering a blueprint for other industries beyond the realm of olive oil production, ultimately catalyzing the realization of carbon-negative products.
Deep eutectic solvents for improved biomass pretreatment: Current status and future prospective towards sustainable processes
(Elsevier Ltd, 2022-11-26) Contreras-Gámez, María del Mar; Galán-Martín, Ángel; Seixas, Nalin; da Costa Lopes, André M.; Silvestre, Armando; Castro, Eulogio
Pretreatment processes — recognized as critical steps for efficient biomass refining — have received much attention over the last two decades. In this context, deep eutectic solvents (DES) have emerged as a novel alternative to conventional solvents representing a step forward in achieving more sustainable processes with both environmental and economic benefits. This paper presents an updated review of the state-of-the-art of DES-based applications in biorefinery schemes. Besides describing the fundamentals of DES composition, synthesis, and recycling, this study presents a comprehensive review of existing techno-economic and life cycle assessment studies. Challenges, barriers, and perspectives for the scale-up of DES-based processes are also discussed.
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, André
This 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.
Dust filter of secondary aluminium industry as raw material of geopolymer foams
(Elsevier, 2020-11) Eliche Quesada, Dolores; Ruiz Molina, Sara; Pérez Villarejo, Luis; Castro, Eulogio; Sánchez Soto, Pedro J.
In this work, the use of waste dust filter of secondary aluminum industry (DFA) to obtain geopolymer foams has been studied. The waste was used as source of alumina and foaming agent. As precursor and principal reactive silica supplier rice husk ash was used. Precursors were chemically activated by means of a sodium hydroxide aqueous solution and a commercial sodium silicate solution. The influence of the DFA content or Si/Al molar ratio (4–7) were determined by keeping the Si/Na molar ratio of 0.7 M constant and the concentration of sodium hydroxide in the activating solution equal to 8.5 M. The geopolymer foams obtained were studied by X-ray Diffraction (XRD), adsorption/desorption of nitrogen, infrared spectroscopy (FTIR), and scanning electron microscope (SEM) techniques. The results indicated that geopolymer foams presented low values of bulk density (643–737 kg/m3) high values of apparent porosity (62–70%), low, but sufficient values of compressive strength (0.5–1.7 MPa) and good values of thermal conductivity (0.131–0.157 W/mK). Lower values of thermal conductivity were obtained for Si/Al = 4 and 5 M ratios, due to the highest apparent porosity and the highest total pore volume. These geopolymer foam materials have similar properties to other construction materials sector such as gypsum boards, foamed concrete, or insulating materials. In addition, its use in other applications of interest such as catalyst support or gas filtration materials could be investigated.
Economic and environmental implications of carbon capture in an olive pruning tree biomass biorefinery
(Elsevier Ltd, 2024-06-01) Fanourakis, Stylianos; Romero-García, Juan Miguel; Castro, Eulogio; Jiménez-Esteller, Laureano; Galán-Martín, Ángel
This study explores the integration of bioenergy with carbon capture and storage (BECCS) in a biorefinery system that converts olive tree prunings into bioethanol and antioxidants. With a capacity to process 1,500 tons of prunings daily, the biorefinery yields an annual production of around 12,000 tons of antioxidants (purity >60 %) and 78,000 tons of bioethanol. Utilizing a holistic approach involving process simulations and life cycle assessment, our analysis covers technical, economic, and environmental dimensions across two scenarios differing in design and heating source: natural gas or a BECCS system using olive prunings. Our findings reveal the potential for BECCS to drastically reduce the carbon footprint, potentially achieving net-negative emissions (−84.37 kg CO2eq per 1.00 kg of bioethanol and 0.15 kg antioxidants produced). However, these environmental gains are counterbalanced by economic and environmental challenges, with investment and operating costs nearly doubling and leading to complex environmental trade-offs related to eutrophication (+75 %), increased water consumption (+45 %), and expanded land use (+80 %). Nevertheless, the premium nature of carbon-negative products, coupled with growing awareness and supportive policy frameworks, may overcome these economic barriers. This study highlights the importance of holistic evaluation when integrating CCS into biorefineries facilitating informed decision-making to address unintended adverse effects and promoting sustainability.
Effect of steel slag and curing temperature on the improvement in technological properties of biomass bottom ash based alkali-activated materials
(Elsevier, 2021-10) Gómez-Casero, Miguel A.; Pérez Villarejo, Luis; Castro, Eulogio; Eliche Quesada, Dolores
In this research the effect of the incorporation of black steel slag (BSS) (25, 50 and 75 wt%) into biomass bottom ash (BBA) as precursor in the synthesis of alkali-activated materials was studied. The alkali-activated pastes were cured at two temperatures, 60 and 20 °C. Thermal curing at 60 °C produced an increase in mechanical properties at early curing ages obtaining similar properties at older ages of 90 days. The addition of up to 50 wt% of BSS resulted in alkali-activated cements with increased compressive and flexural strengths. The increase in mechanical properties could be due to the formation of a higher amount of calcium aluminosilicate gel (C-A-H-S) with respect to potassium aluminosilicate gel (K-A-H-S) or to the synergistic formation of C-K-A-S-H gel. Therefore, these specimens can be used as a binding material for concrete production to replace Portland cement, which can lead to significant environmental and socio-economic improvements by reducing CO2 emissions and consumption of natural resources.
Improved xylitol production from olive stones hydrolysates by biological detoxification
(Elsevier, 2022) Romero-García, Juan MIguel; Fehér, Csaba; Cara, Cristóbal; Ruiz-Ramos, Encarnación; Castro, Eulogio
Olive stones, currently used as a biosource of heat and power, is gaining research interest as a feedstock for a biorefinery based on olive derived wastes. In this work, pure xylitol crystals were obtained and fully characterized as one of the possibilities of taking full advantage of this by-product of olive oil production. The proposed process includes a two-step pretreatment (water and acid extractions), detoxification of the liquid fractions and fermentation of sugars. After the water extraction, a liquid fraction with antioxidant capacity was recovered; the second step was done with dilute sulfuric acid for solubilization of sugars, resulting in a solution containing more than 60 g/l of xylose as the main sugar. This liquor contained also up to 16 g/l acetic acid, which rendered it not fermentable. Also other compounds, potentially inhibitors in downstream operations, were produced during the pretreatment, requiring a detoxification procedure. In this work, a chemical-free, biological treatment with Saccharomyces cerevisiae proved to be the best detoxification method, as glucose, furfural, hydroxymethylfurfural and acetic acid were consumed. The subsequent inoculation of Candida boidinii produced xylitol concentrations above 38 g/l after 90h fermentation time and a yield as high as 63%, equivalent to 12 g xylitol/100 g olive stones.
Integrated techno-economic and environmental assessment of biorefineries: review and future research directions
(Royal Society of Chemistry, 2023-06-12) Pérez-Almada, Déborah; Galán-Martín, Ángel; Contreras, María del Mar; Castro, Eulogio
Biorefineries will be strategic players in achieving the circular economy and sustainability goals. This work presents a comprehensive review of the last decade of research on the Environmental and TechnoEconomic Assessment (ETEA) of biorefineries. We compiled 102 articles applying an integrated ETEA approach to understand the technical, economic, and environmental implications of different biorefinery schemes. Bibliometric analysis has been first performed to map the keywords and locations of case studies and explore trends in biomass feedstock, conversion routes, and bio-based products. Then, computer-aided tools and state-of-the-art methodologies employed within the ETEA framework are reviewed. Finally, challenges and directions for research are discussed. The results show increasing interest in the topic, moving from the first to higher generations. Publications utilizing secondgeneration biomass dominate the research topic (65%), followed by the third, first, and fourth generations (16, 12, and 1%, respectively). An uneven distribution of publications was also observed, with the USA contributing the most (with one-third of studies), suggesting that governments are crucial driving forces of research. Biochemical routes such as fermentation and anaerobic digestion receive the most attention (together used in 59 out of the 102 articles), followed by thermochemical routes (e.g., combustion, pyrolysis, and gasification used in 28% of the articles). Bioethanol is the main targeted product (in 29 articles), followed by biogas, biomethane, and biodiesel. Overall, the ETEA framework aids in designing and optimizing biorefineries to achieve sustainability goals. It helps evaluate the trade-offs between the economic viability and environmental sustainability of conventional and emerging biorefinery processes at different stages of deployment. This review contributes to the development of the ETEA framework, and it might be helpful to guide practitioners, decision-making, and future research on sustainable biorefineries.
Low energy-demanding recovery of antioxidants and sugars from olive stones as preliminary steps in the bioreﬁnery context
(Elsevier, 2014-06-22) Lama-Munñoz, Antonio; Romero-García, Juan M.; Cara, Cristóbal; Moya, Manuel; Castro, Eulogio
Olive stones constitute the main solid by-product of the olive oil extraction process. As a lignocellulosic material, their use as a source of fermentable sugars, antioxidants and other applications has been proposed. In this work the possibilities of a better use of this material through a relatively low energy-demanding operation, e.g. autoclave treatment, are assessed. Dilute acid extraction was used for evaluating the influence of the main variables (temperature, acid concentration and pretreatment time) on the sugar composition and the antioxidant capacity of liquid fractions (prehydrolyzates) issued from autoclave treatment. Results show that the highest production of fermentable sugars, 27 g/100 g initial dry matter, was obtained at the most severe pretreatment conditions (130 ◦C for 90 min and 2% sulfuric acid), with xylose being 90% of the released sugars, while cellulose degradation was limited. Concerning antioxidant capacity of the prehydrolyzates, the best result was obtained at the highest temperatura (130 ◦C) and time (90 min) but using no acid. This procedure is proposed as a preliminary step of a broader treatment scheme which can also include further steps of pretreatment and eventually enzymatic hydrolysis and fermentation. As a conclusion, a two-step process strategy is suggested to optimize the recovery of antioxidants in the first step, and the production of fermentable sugars in the second step.
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, Eulogio
Olive-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.
Optimization of ultrasound-assisted extraction of biomass from olive trees using response surface methodology
(Elsevier, 2019) Martínez-Patiño, José Carlos; Gullón, Beatriz; Romero, Inmaculada; Ruiz, Encarnación; Brnčić, Mladen; Žlabur, Jana Šic; Castro, Eulogio
Olive tree pruning biomass (OTP) and olive mill leaves (OML) are the main residual lignocellulosic biomasses that are generated from olive trees. They have been proposed as a source of value-added compounds and biofuels within the biorefinery concept. In this work, the optimization of an ultrasound-assisted extraction (UAE) process was performed to extract antioxidant compounds present in OTP and OML. The effect of the three parameters, ethanol/water ratio (20, 50, 80% of ethanol concentration), amplitude percentage (30, 50, 70%) and ultrasonication time (5, 10, 15 min), on the responses of total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activities (DPPH, ABTS and FRAP) were evaluated following a Box–Behnken experimental design. The optimal conditions obtained from the model, taking into account simultaneously the five responses, were quite similar for OTP and OML, with 70% amplitude and 15 min for both biomasses and a slight difference in the optimum concentration of ethanol. (54.5% versus 51.3% for OTP and OML, respectively). When comparing the antioxidant activities obtained with OTP and OML, higher values were obtained for OML (around 40% more than for OTP). The antioxidant activities reached experimentally under the optimized conditions were 31.6 mg of TE/g of OTP and 42.5 mg of TE/g of OML with the DPPH method, 66.5 mg of TE/g of OTP and 95.9 mg of TE/g of OML with the ABTS method, and 36.4 mg of TE/g of OTP and 49.7 mg of TE/g of OML with the FRAP method. Both OTP and OML could be a potential source of natural antioxidants.
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, Eulogio
Olive-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.
Techno-economic and Environmental Assessment of an Olive Stone based Biorefinery
(Elsevier, 2014-10-03) Hernández, Valentina; Romero-García, Juan M.; Dávila, Javier A.; Castro, Eulogio; Cardona, Carlos A.
Olive tree cultivation is spreading worldwide as a consequence of beneficial effects of olive oil consumption. Olive oil production process and table olive industries are the major sources of olive stones. Currently, this by-product is used in direct combustion to produce energy as electricity or heat. However, there are other possibilities for taking full advantage of a renewable source of interesting compounds. In this work the techno-economic and environmental assessment of two biorefinery schemes and its comparison with the direct combustion (base case) of this residue are presented. The first biorefinery scheme describes the integrated production of xylitol, furfural, ethanol and poly-3-hydroxybutyrate (PHB). The second biorefinery scheme considers the production of xylitol, furfural, ethanol and PHB integrated to a cogeneration system for producing bioenergy from the solid residues resulting from the mentioned processes. The results showed that in the first biorefinery scheme, the net profit margin is approximately 53%, while the second present a net profit margin of 6%.
Xylitol production by Debaryomyces hansenii and Candida guilliermondii from rapeseed straw hemicellulosic hydrolysate
(Elsevier, 2018) López-Linares, Juan Carlos; Romero, Inmaculada; Cara, Cristóbal; Castro, Eulogio; Mussatto, Solange
This study evaluated the possibility of using rapeseed straw hemicellulosic hydrolysate as a fermentation medium for xylitol production. Two yeast strains, namely Debaryomyces hansenii and Candida guilliermondii, were used for this bioconversion process and their performance to convert xylose into xylitol was compared. Additionally, different strategies were evaluated for the hydrolysate detoxification before its use as a fermentation medium. Assays in semi-defined media containing different combinations of sugars were also performed in order to verify the influence of hexose sugars on xylose metabolism by the yeasts. C. guilliermondii exhibited higher tolerance to the toxic compounds than D. hansenii. Not only the toxic compounds present in the hydrolysate affected the yeast´s performance to convert xylose into xylitol, but glucose also had a negative impact on the bioconversion process. It was not necessary to completely eliminate the toxic compounds to obtain an efficient conversion of xylose into xylitol, mainly by C. guilliermondii.

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Examinando por Autor "Castro, Eulogio"