Biocidal and synergistic effect of three types of biologically synthesised silver/silver chloride nanoparticles.

Three types of silver/silver chloride nanoparticles were obtained by green synthesis from three types of microbial biomass. Their biocidal capacity was tested against six microorganisms. Two filamentous fungi were used that had previously demonstrated the ability to synthesise nanoparticles, Penicillium sp. 8L2 and Botryosphaeria rhodina MAMB-05. Also, the synthesis capacity of a yeast, Rhodotorula mucilaginosa 1S1, was evaluated. The original protocols underwent slight modifications. At the same time, the fractional inhibitory concentration was obtained. The interaction between specific antibiotics and the nanoparticles that showed the greatest biocidal capacity came from Penicillium sp.8L2, and it was studied further. All nanoparticles were characterised by UV-vis spectrophotometry and transmission electron microscopy (TEM). Also, their size distribution was analysed, which was in the range of 4 to 34 nm. The biocidal capacity of the nanoparticles for a group of bacteria and fungi was studied, presenting very low values in the range of 2.5-10 µg/mL for bacteria and 4-256 µg/mL for fungi. The interactions between the nanoparticles synthesised by Penicillium sp. 8L2 and a group of specific antibiotics for the tested microorganisms were also studied, proving that there was a synergistic interaction with vancomycin and ciprofloxacin and Staphylococcus epidermidis CECT 4183 and Escherichia coli CECT 101 bacteria, respectively.

Fe3O4@UiO-66-NH2 based on magnetic solid phase extraction for determination of organic UV filters in environmental water samples.

In this work, a nanocomposite structured magnetic metal-organic framework named as Fe3O4@UiO-66-NH2 was prepared via a simple hydrothermal approach. The as-mentioned nanocomposite was characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and the Brunauer-Emmett-Teller (BET) techniques. Using the Fe3O4@UiO-66-NH2 as a nanosorbent, an easy and highly effective approach was developed to preconcentrate nine organic UV filters before gas chromatography-mass spectrometry (GC-MS) analysis. Different conditions influencing the extraction efficiency encompassing the sorbent amount, nature and volume of desorption solvent, desorption time, pH of the sample, and extraction time, were examined. Under the optimal experimental parameters, the Fe3O4@UiO-66-NH2-based magnetic solid phase extraction and GC-MS (MSPE-GC-MS) demonstrated linearity in the range of 0.03-1500 ng/L (R2 ≥ 0.9974) and the reproducibility, expressed as RSD, was ≤7.5%. The limits of detection ranged between 0.01 and 0.07 ng/L and limits of quantification were in the range of 0.03-0.4 ng/L. Finally, the suggested approach was satisfactorily utilized to determine nine organic UV filters in different water samples (analytical recoveries between 86.5% and 104.2%).

Fermentative valorisation of xylose-rich hemicellulosic hydrolysates from agricultural waste residues for lactic acid production under non-sterile conditions.

Lactic acid (LA) is a platform chemical with diverse industrial applications. Presently, commercial production of LA is dominated by microbial fermentation using sugary or starch-based feedstocks. Research pursuits emphasizing towards sustainable production of LA using non-edible and renewable feedstocks have accelerated the use of lignocellulosic biomass (LCB). The present study focuses on the valorisation of xylose derived from sugarcane bagasse (SCB) and olive pits (OP) through hydrothermal and dilute acid pretreatment, respectively. The xylose-rich hydrolysate obtained was used for LA production by homo-fermentative and thermophilic Bacillus coagulans DSM2314 strain under non-sterile conditions. The fed-batch mode of fermentation resulted in maximum LA titers of 97.8, 52.4 and 61.3 g/L with a yield of 0.77, 0.66 and 0.71 g/g using pure xylose, xylose-rich SCB and OP hydrolysates, respectively. Further, a two-step aqueous two-phase system (ATPS) extraction technique was employed for the separation and recovery of LA accumulated on pure and crude xylose. The LA recovery was 45 - 65% in the first step and enhanced to 80-90% in the second step.The study demonstrated an efficient integrated biorefinery approach to valorising the xylose-rich stream for cost-effective LA production and recovery.

Apricot Seed Shells and Walnut Shells as Unconventional Sugars and Lignin Sources.

The present study focuses on using apricot seeds shells and walnut shells as a potential renewable material for biorefinery in Ukraine. The goal of the research work was to determine the relationship between the chemical composition of solid residues from biomass after acid pretreatment with H2SO4, alkaline pretreatment with NaOH, and a steam explosion pretreatment and the recovery of sugars and lignin after further enzymatic hydrolysis with the application of an industrial cellulase Cellic CTec2. Apricot seeds shells and walnut shells consist of lots of cellulose (35.01 and 24.19%, respectively), lignin (44.55% and 44.63%, respectively), hemicelluloses (10.77% and 26.68%, respectively), and extractives (9.97% and 11.41%, respectively), which affect the efficiency of the bioconversion of polysaccharides to sugars. The alkaline pretreatment was found to be more efficient in terms of glucose yield in comparison with that of acid and steam explosion, and the maximum enzymatic conversions of cellulose reached were 99.7% and 94.6% for the solids from the apricot seeds shells and the walnut shells, respectively. The maximum amount of lignin (82%) in the residual solid was obtained during the processing of apricot seed shells submitted to the acid pretreatment. The amount of lignin in the solids interferes with the efficiency of enzymatic hydrolysis. The results pave the way for the efficient and perspective utilization of shells through the use of inexpensive, simple and affordable chemical technologies, obtaining value-added products, and thus, reducing the amount of environmental pollution (compared to the usual disposal practice of direct burning) and energy and material external dependency (by taking advantage of these renewable, low-cost materials).

Ag(I) Biosorption and Green Synthesis of Silver/Silver Chloride Nanoparticles by Rhodotorula mucilaginosa 1S1.

The efficiency of Rhodotorula mucilaginosa 1S1 as an Ag(I) biosorbent and at the same time its ability to biosynthesize recoverable silver nanoparticles is evaluated. Kinetic, equilibrium and thermodynamic tests are carried out for 19 °C, 27 °C and 37 °C, from which the process is adjusted to a pseudo second-order kinetics and to the Freundlich model, while optimal operational conditions are determined at 27 °C. The thermodynamic study shows positive values for enthalpy (ΔH: 133.23 kJ/mol) and entropy (ΔS: 0.4976 kJ/(mol K)), while the Gibbs free energy (ΔG) value is 12.136 kJ/mol. For a metal concentration of 459 mg/L, a maximum biosorption capacity (qm) of 137.2 mg/g at 19 °C is obtained, while for 100 mg/L concentration a qm value of 60.44 mg/g is obtained at the same temperature. The mechanisms involved in the biosorption process are studied by infrared spectroscopy, X-ray diffraction and scanning and transmission electron microscopy, while the nanoparticle synthesis is evaluated by ultraviolet-visible spectrophotometry (UV-vis) and transmission electron microscopy. The results indicate that the biomass is a good biosorbent and also has the ability to synthesize silver nanoparticles (Ag/AgCl) with sizes between 12 nm and 20 nm.

Deep eutectic solvents for improved biomass pretreatment: Current status and future prospective towards sustainable processes.

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.

Grapevine Shoot Extract Rich in Trans-Resveratrol and Trans-ε-Viniferin: Evaluation of Their Potential Use for Cardiac Health.

A 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.

Hepatopreventive properties of hydroxytyrosol and mannitol-rich extracts obtained from exhausted olive pomace using green extraction methods.

Exhausted 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.

Optimization of Microwave-Assisted Water Extraction to Obtain High Value-Added Compounds from Exhausted Olive Pomace in a Biorefinery Context.

Microwave-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.

Biotechnological use of the ubiquitous fungus Penicillium sp. 8L2: Biosorption of Ag(I) and synthesis of silver nanoparticles.

In this work, the efficiency of the ubiquitous fungus Penicillium sp. 8L2 to remove Ag(I) ions from synthetic solutions and its potential to synthesize silver nanoparticles (AgNPs) was evaluated. Using a Rotatable Central Composite Design pH and biomass concentration were optimized. Maximum biosorption capacity 51.53 mg/g, by Langmuir model, comparing favourably with other reports. The fungal biomass was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and analyzed before and after the biosorption process by different techniques: X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Ultra-High Resolution Transmission Electron Microscopy and Energy Dispersive X-ray (HR-TEM-EDX) and Ultraviolet-Visible Spectrophotometry (UV-vis). The results showed that the fungus applied several mechanisms to remove Ag(I) ions from the solution and that some of them induced the synthesis of AgNPs. This fact could be verified in the synthesis tests from the cell extract in which aqueous suspensions with high concentrations of AgNPs were obtained. These nanoparticles had diameters between 2 and 9 nm and therefore a high potential for their use as biocidal agents. The results indicated that the synthesis of nanoparticles could be an added value to the heavy metal biosorption process.

Valorization of renewable resources to functional oligosaccharides: Recent trends and future prospective.

Lignocellulosic wastes have the ability to be transformed into oligosaccharides and other value-added products. The synthesis of oligosaccharides from renewable sources bestow to growing bioeconomies. Oligosaccharides are synthesized chemically or biologically from agricultural residues. These oligosaccharides are functional food supplements that have a positive impact on humans and livestock. Non-digestible oligosaccharides, refered as prebiotics are beneficial for the colonic microbiota inhabiting the f the digestive system. These microbiota plays a crucial role in stimulating the host immune system and other physiological responses. The commonly known prebiotics, galactooligosaccharides (GOS), xylooligosaccharides (XOS), fructooligosaccharides (FOS), mannanooligosaccharides (MOS), and isomaltooligosaccharides (IOS) are synthesized either through enzymatic or whole cell-mediated approaches using natural or agricultural waste substrates. This review focusses on recent advancements in biological processes, for the synthesis of oligosaccharides using renewable resources (lignocellulosic substrates) for sustainable circular bioeconomy. The work also addresses the limitations associated with the processes and commercialization of the products.

Process optimisation for production and recovery of succinic acid using xylose-rich hydrolysates by Actinobacillus succinogenes.

Succinic acid (SA) is a top platform chemical obtainable from biomass. The current study evaluated the potential of Actinobacillus succinogenes for SA production using xylose-rich hemicellulosic fractions of two important lignocellulosic feedstocks, olive pits (OP) and sugarcane bagasse (SCB) and the results were compared with pure xylose. Initial experiments were conducted in shake flask followed by batch and fed-batch cultivation in bioreactor. Further separation of SA from the fermented broth was carried out by adapting direct crystallisation method. During fed-batch culture, maximum SA titers of 36.7, 33.6, and 28.7 g/L was achieved on pure xylose, OP and SCB hydrolysates, respectively, with same conversion yield of 0.27 g/g. The recovery yield of SA accumulated on pure xylose, OP and SCB hydrolysates was 79.1, 76.5, and 75.2%, respectively. The results obtained are of substantial value and pave the way for development of sustainable SA biomanufacturing in an integrated biorefinery.

Sequential Extraction of Hydroxytyrosol, Mannitol and Triterpenic Acids Using a Green Optimized Procedure Based on Ultrasound.

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.

High level xylitol production by Pichia fermentans using non-detoxified xylose-rich sugarcane bagasse and olive pits hydrolysates.

Hemicellulosic sugars, the overlooked fraction of lignocellulosic residues can serve as potential and cost-effective raw material that can be exploited for xylitol production. Xylitol is a top platform chemical with applications in food and pharmaceutical industries. Sugarcane bagasse (SCB) and olive pits (OP) are the major waste streams from sugar and olive oil industries, respectively. The current study evaluated the potential of Pichia fermentans for manufacturing of xylitol from SCB and OP hydrolysates through co-fermentation strategy. The highest xylitol accumulation was noticed with a glucose and xylose ratio of 1:10 followed by feeding with xylose alone. The fed-batch cultivation using pure xylose, SCB, and OP hydrolysates, resulted in xylitol accumulation of 102.5, 86.6 and 71.9 g/L with conversion yield of 0.78, 0.75 and 0.74 g/g, respectively. The non-pathogenic behaviour and ability to accumulate high xylitol levels from agro-industrial residues demonstrates the potential of P. fermentans as microbial cell factory.

Biosorption mechanisms of Ag(I) and the synthesis of nanoparticles by the biomass from Botryosphaeria rhodina MAMB-05.

Two biomass types of Botryosphaeria rhodina MAMB-05 (VMSM and M3) were evaluated to determine their effectiveness in removing Ag(I) ions from synthetic solutions. Both biomass types obtained good results in the biosorption process with maximum biosorption capacities (qm) for the Langmuir model of 34.67 and 39.23 mg Ag(I)/g dry biomass for M3 and VMSM, respectively. The biomass was characterized by X-ray microfluorescence and Fourier-transform-infrared spectroscopy (FT-IR). After the biosorption process, the mechanisms involved in biosorption were studied by FT-IR, X-ray diffraction (XRD), Field Emission Scanning Microscopy/Energy Dispersive X-ray Analysis (FESEM/EDX) and Ultraviolet-Visible Spectrophotometry. The results demonstrated the participation of various mechanisms in the retention of silver on biomass (bioadsorption, complexation, ion exchange, covalent bonding) that resulted in the formation of silver chloride nanoparticles (AgCl-NPs) and silver nanoparticles (AgNPs). The sizes of AgCl-NPs (chlorargyrite) according to the Debye-Scherrer equation were 19.29 nm (VMSM biomass) and 24.9 nm for the M3 type. For AgNPs the crystal size was between 1.5 and 0.8 nm for VMSM and M3 respectively. Furthermore, it was found that an undetermined fraction of the silver nanoparticles after biosorption remained in solution, which could be advantageous for their recovery.

Recovery of Bioactive Compounds from Industrial Exhausted Olive Pomace through Ultrasound-Assisted Extraction.

Exhausted 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.

Correction: Gómez-Cruz et al. Valorisation of Exhausted Olive Pomace by an Eco-Friendly Solvent Extraction Process of Natural Antioxidants. Antioxidants 2020, 9, 1010.

The author wishes to make the following correction to this paper [...].

Olive Pomace-Derived Biomasses Fractionation through a Two-Step Extraction Based on the Use of Ultrasounds: Chemical Characteristics.

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.

Valorisation of Exhausted Olive Pomace by an Eco-Friendly Solvent Extraction Process of Natural Antioxidants.

Exhausted 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 ºC, 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.

Optimization with Response Surface Methodology of Microwave-Assisted Conversion of Xylose to Furfural.

The production of furfural from renewable sources, such as lignocellulosic biomass, has gained great interest within the concept of biorefineries. In lignocellulosic materials, xylose is the most abundant pentose, which forms the hemicellulosic part. One of the key steps in the production of furfural from biomass is the dehydration reaction of the pentoses. The objective of this work was to assess the conditions under which the concentration of furfural is maximized from a synthetic, monophasic, and homogeneous xylose medium. The experiments were carried out in a microwave reactor. FeCl3 in different proportions and sulfuric acid were used as catalysts. A two-level, three-factor experimental design was developed for this purpose. The results were further analyzed through a second experimental design and optimization was performed by response surface methodology. The best operational conditions for the highest furfural yield (57%) turned out to be 210 °C, 0.5 min, and 0.05 M FeCl3.