RESUMEN
Concentrated liquid coffees (CLCs) refer to stored extracts stable at environmental temperature, used as ingredients in the retail market. Their low chemical stability affects the sensory profile. This study was performed in two CLCs, one without additives (BIB) and another with a mix of sodium benzoate and potassium sorbate additives (SD), stored at 25 °C for one year. Quantitative-Descriptive (QDA) and discriminant analyses permitted identifying the critical sensory attributes and their evolution over time. The concentrate without additives presented an acceptance limit of 196 days (evaluated at a 50% acceptance ratio), while the additives increased the shelf life up to 226 days (38.9% improvement). The rejection was related to a decreased aroma, increased acidity, and reduced bitterness. A bootstrapped feature selection version of Partial Least Square analysis further demonstrated that reactions of 5-caffeoylquinic acid (5CQA) and 3,5-dicaffeoylquinic acid (3,5diCQA) could cause changes in the aroma at the first degradation stage. In the following stages, changes in fructose and stearic acid contents, a key indicator of acceptance for both extracts possibly related to non-enzymatic reactions involving fructose and other compounds, might affect the bitterness and acidity. These results provided valuable information to understand flavor degradation in CLCs.
Asunto(s)
Café/química , Aromatizantes/química , Fructosa/química , Análisis de los Mínimos Cuadrados , Odorantes , Benzoato de Sodio/química , Ácido Sórbico/química , Ácidos Esteáricos/química , Gusto/efectos de los fármacos , TemperaturaRESUMEN
The present work reports the development of a novel electrochemical sensor for the selective detection of fructose. The sensor was developed through electropolymerization of a molecularly imprinted polymer film on a reduced graphene oxide modified electrode. The modified electrode was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, atomic force microscopy and RAMAN spectroscopy. Through the application of the modified electrode, the recognition of fructose molecules occurred in a concentration range of 1.0 × 10-14 to 1.0 × 10-11 mol L-1, under a Langmuir adsorption isothermal model. The sensitivity and limits of detection and quantification obtained for the sensor were 9.9 × 107 A L mol-1, 3.2 × 10-15 mol L-1 and 1.1 × 10-14 mol L-1, respectively. The analytical method used for the detection of fructose presented good reproducibility, stability and accuracy, and was successfully applied for the quantification of this sugar in orange, apple and grape juices.
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Electroquímica/instrumentación , Análisis de los Alimentos/instrumentación , Fructosa/análisis , Jugos de Frutas y Vegetales/análisis , Grafito/química , Polímeros Impresos Molecularmente/química , Electrodos , Fructosa/química , Límite de Detección , Polímeros Impresos Molecularmente/síntesis química , Reproducibilidad de los ResultadosRESUMEN
Aspergillus oryzae ß-galactosidase was immobilized in in-house quaternary ammonium agarose (QAA) and used for the first time in the synthesis of lactulose. A biocatalyst was obtained with a specific activity of 24,690 IUHâg-1; protein immobilization yield of 97% and enzyme immobilization yield of 76% were obtained at 30 °C in 10 mM phosphate buffer pH 7 for standard size agarose at 100 mgproteinâgsupport-1 which the maximum protein load of QAA. Highest yield and specific productivity of lactulose were 0.24 gâg-1 and 9.78 gâg-1 h-1 respectively, obtained at pH 6, 100 IUHâg lactose-1 enzyme/lactose ratio and 12 lactose/fructose molar ratio. In repeated-batch operation with the immobilized enzyme, the cumulative mass of lactulose per unit mass of contacted protein and cumulative specific productivity were higher than obtained with the soluble enzyme since the first batch. After enzyme activity exhaustion, the enzyme was desorbed and QAA support was reused without alteration in its maximum enzyme load capacity and without detriment in yield, productivity and selectivity in the batch synthesis of lactulose with the resulting biocatalyst. This significantly decreases the economic impact of the support, presenting itself as a distinctive advantage of immobilization by ionic interaction.
Asunto(s)
Aspergillus oryzae/enzimología , Enzimas Inmovilizadas/química , Lactulosa/síntesis química , beta-Galactosidasa/química , Catálisis , Cromatografía Líquida de Alta Presión , Fructosa/química , Concentración de Iones de Hidrógeno , Lactosa/química , Tamaño de la Partícula , Sefarosa/química , TemperaturaRESUMEN
A series of defect pyrochlores of the composition (H3O)1+pSb1+pTe1-pO6 have been prepared by ion exchange from K-containing pyrochlores K1+pSb1+pTe1-pO6 in sulfuric acid at 280 °C for 24 h. The structural characterization of the hydronium-containing pyrochlores, including the location of the H3O+ units within the three-dimensional framework, was possible from neutron powder diffraction data in undeuterated samples. The crystal structure for all the compounds is defined in the Fd3[combining macron]m space group, and consists of a covalent framework of SbVO6 and TeVIO6 octahedra distributed at random and connected by their vertices with (Sb,Te)-O1-(Sb,Te) angles close to 136°, conforming to large cages where the hydronium species are located off-center. The absence of K+ ions in the ion-exchanged pyrochlores was confirmed by inductively coupled plasma optical emission spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The shape and size of the hydronium units evolve along with the series, becoming more compact as the framework covalence and Lewis-basicity decrease upon Sb enrichment of the structure (for greater p values). The amount and lability of the H3O+ species also increase throughout the series, as wanted: a straightforward correlation of the catalytic activity in the fructose dehydration reaction to 5-hydroxymethylfurfural has been observed, reaching conversion rates up to 88.5% of concentrated fructose solution for the p = 0.25 catalyst. Moreover, a pseudo-first-order kinetic mechanism was simulated, and the kinetic constants obtained from diluted and concentrated enhanced reaction systems were determined and compared.
Asunto(s)
Antimonio/química , Fructosa/química , Niobio/química , Compuestos Onio/química , Óxidos/química , Telurio/química , Catálisis , Deshidratación , Furaldehído/análogos & derivados , Furaldehído/química , Calor , Isomerismo , Conformación Molecular , Difracción de Polvo , Factores de Tiempo , Difracción de Rayos XRESUMEN
Background: Burdock (Arctium lappa L.) is a fructan-rich plant with prebiotic potential. The aim of this study was to develop an efficient enzymatic route to prepare fructooligosaccharides (FOS)-rich and highly antioxidative syrup using burdock root as a raw material. Results: Endo-inulinase significantly improved the yield of FOS 2.4-fold while tannase pretreatment further increased the yield of FOS 2.8-fold. Other enzymes, including endo-polygalacturonase, endo-glucanase and endo-xylanase, were able to increase the yield of total soluble sugar by 11.1% (w/w). By this process, a new enzymatic process for burdock syrup was developed and the yield of burdock syrup increased by 25% (w/w), whereas with FOS, total soluble sugars, total soluble protein and total soluble polyphenols were enhanced to 28.8%, 53.3%, 8.9% and 3.3% (w/w), respectively. Additionally, the scavenging abilities of DPPH and hydroxyl radicals, and total antioxidant capacity of the syrup were increased by 23.7%, 51.8% and 35.4%, respectively. Conclusions: Our results could be applied to the development of efficient extraction of valuable products from agricultural materials using enzyme-mediated methods.
Asunto(s)
Oligosacáridos/química , Raíces de Plantas/química , Fructosa/química , Glicósido Hidrolasas/metabolismo , Antioxidantes/química , Oligosacáridos/metabolismo , Poligalacturonasa/metabolismo , Hidrolasas de Éster Carboxílico/metabolismo , Cromatografía Líquida de Alta Presión , Radical Hidroxilo , Arctium , Alimentos Funcionales , Polifenoles , Fructosa/metabolismo , Antioxidantes/metabolismoRESUMEN
Prebiotic fructooligosaccharides (FOS) are currently obtained by enzymatic reaction with fructosyltransferases (FTFs) using sucrose as both donor and acceptor. In these reactions glucose results as the most abundant by-product, arising from each fructosyl transfer event and, together with fructose, because of the inherent hydrolytic activity of the FTFs. As FOS are mainly used as prebiotic in nutraceutical foods, the reduction or total elimination of monosaccharides is required. In this work the selective elimination of monosaccharides from a synthetic FOS mixture was achieved through the selective complexation of glucose and fructose with phenyl boronic acid (PBAc) followed by ethyl-acetate extraction. The process was applied to a complex mixture of FOS obtained in an enzymatic synthesis reaction containing 40% glucose, 15.8% fructose and 35% of FOS, elimination of the sugars was achieved through 3:1 molar reactions, resulting in a levan-type FOS product with 97% purity.
Asunto(s)
Ácidos Borónicos/metabolismo , Monosacáridos/metabolismo , Oligosacáridos/aislamiento & purificación , Acetatos/química , Ácidos Borónicos/química , Cromatografía en Capa Delgada , Escherichia coli/metabolismo , Fructosa/química , Glucosa/química , Glicósido Hidrolasas/genética , Glicósido Hidrolasas/metabolismo , Hexosiltransferasas/genética , Hexosiltransferasas/metabolismo , Extracción Líquido-Líquido , Monosacáridos/química , Oligosacáridos/química , Oligosacáridos/metabolismo , Prebióticos/análisis , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/genéticaRESUMEN
Extracellular polysaccharides (EPS) could increase the penetration of fluoride through dental biofilm, reducing its cariogenicity. We measured the concentration of fluoride in EPS-containing (EPS+) or not-containing (EPS-) Streptococcus mutans bacterial pellets resembling test biofilms, before and up to 60 min after a 0.05% NaF rinse in situ. Fluoride penetration and clearance were higher in EPS+ bacterial pellets. The data suggest that EPS enhances fluoride penetration, but also accelerates fluoride clearance from dental biofilms.
Asunto(s)
Biopelículas/efectos de los fármacos , Cariostáticos/química , Fluoruros/química , Polisacáridos Bacterianos/química , Streptococcus mutans/efectos de los fármacos , Adulto , Cariostáticos/farmacología , Estudios Cruzados , Caries Dental/microbiología , Difusión , Método Doble Ciego , Fluoruros/farmacología , Fructosa/química , Glucosa/química , Humanos , Concentración Osmolar , Análisis de Regresión , Saliva/fisiología , Estadísticas no Paramétricas , Streptococcus mutans/fisiología , Sacarosa/químicaRESUMEN
Menopause is associated with bone loss. Prebiotics increase Ca, inorganic phosphorus (Pi), and Mg absorption, improving bone health. These increases would supply an extra amount of minerals, decreasing bone resorption and possibly reversing ovariectomy-induced bone loss. The present experimental study sought to evaluate the effect of adding a prebiotic GOS/FOS® mixture to a normal or a low Ca diet on Ca, Pi, and Mg absorption, in osteopenic rats. Four groups of n = 8 rats each were OVX, and 8 rats were SHAM operated. All rats were fed a commercial diet for 45 days. They were then fed one of the following diet for 45 days: C-0.5%: SHAM fed AIN 93 M containing 0.5%Ca; O-0.5% and O-0.3%: OVX rats fed AIN 93 M, containing 0.5% or 0.3%Ca, respectively; GF-0.5% and GF-0.3%: OVX rats fed AIN 93 M, containing 0.5% or 0.3%Ca+ 2.5% GOS/FOS®, respectively. At the end of the experimental time point, Ca, P, and MgAbs% was significantly higher in GF-0.5% and GF-0.3% as compared to the remaining groups (p < 0.01). Irrespective of diet Ca content, CTX decreased whereas femur Ca and P content, tibia BV/TV and GPC.Th, lumbar spine and proximal tibia BMD, bone strength, bone stiffness, and elastic modulus increased in the GF-0.5% and GF-0.3% groups as compared to O-0.5% and O-0.3%, respectively (p < 0.05). This prebiotic mixture would be a useful tool to prevent the increase in bone loss associated with menopause and aging.
Asunto(s)
Enfermedades Óseas Metabólicas/metabolismo , Huesos/efectos de los fármacos , Calcio de la Dieta , Dieta , Absorción Intestinal/efectos de los fármacos , Oligosacáridos/farmacología , Animales , Densidad Ósea/efectos de los fármacos , Enfermedades Óseas Metabólicas/etiología , Enfermedades Óseas Metabólicas/patología , Huesos/fisiología , Calcio/deficiencia , Calcio/metabolismo , Calcio/farmacocinética , Calcio de la Dieta/administración & dosificación , Calcio de la Dieta/farmacocinética , Dieta/métodos , Suplementos Dietéticos , Femenino , Fructosa/química , Fructosa/farmacología , Galactosa/química , Galactosa/farmacología , Oligosacáridos/administración & dosificación , Ovariectomía , Ratas , Ratas WistarRESUMEN
BACKGROUND: Sugarcane bagasse has been proposed as a lignocellulosic residue for second-generation ethanol (2G) produced by breaking down biomass into fermentable sugars. The enzymatic cocktails for biomass degradation are mostly produced by fungi, but low cost and high efficiency can consolidate 2G technologies. A. fumigatus plays an important role in plant biomass degradation capabilities and recycling. To gain more insight into the divergence in gene expression during steam-exploded bagasse (SEB) breakdown, this study profiled the transcriptome of A. fumigatus by RNA sequencing to compare transcriptional profiles of A. fumigatus grown on media containing SEB or fructose as the sole carbon source. Secretome analysis was also performed using SDS-PAGE and LC-MS/MS. RESULTS: The maximum activities of cellulases (0.032 U mL-1), endo-1,4-ß--xylanase (10.82 U mL-1) and endo-1,3-ß glucanases (0.77 U mL-1) showed that functional CAZymes (carbohydrate-active enzymes) were secreted in the SEB culture conditions. Correlations between transcriptome and secretome data identified several CAZymes in A. fumigatus. Particular attention was given to CAZymes related to lignocellulose degradation and sugar transporters. Genes encoding glycoside hydrolase classes commonly expressed during the breakdown of cellulose, such as GH-5, 6, 7, 43, 45, and hemicellulose, such as GH-2, 10, 11, 30, 43, were found to be highly expressed in SEB conditions. Lytic polysaccharide monooxygenases (LPMO) classified as auxiliary activity families AA9 (GH61), CE (1, 4, 8, 15, 16), PL (1, 3, 4, 20) and GT (1, 2, 4, 8, 20, 35, 48) were also differentially expressed in this condition. Similarly, the most important enzymes related to biomass degradation, including endoxylanases, xyloglucanases, ß-xylosidases, LPMOs, α-arabinofuranosidases, cellobiohydrolases, endoglucanases and ß-glucosidases, were also identified in the secretome. CONCLUSIONS: This is the first report of a transcriptome and secretome experiment of Aspergillus fumigatus in the degradation of pretreated sugarcane bagasse. The results suggest that this strain employs important strategies for this complex degradation process. It was possible to identify a set of genes and proteins that might be applied in several biotechnology fields. This knowledge can be exploited for the improvement of 2G ethanol production by the rational design of enzymatic cocktails.
Asunto(s)
Aspergillus fumigatus/crecimiento & desarrollo , Celulosa/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Perfilación de la Expresión Génica/métodos , Aspergillus fumigatus/genética , Aspergillus fumigatus/metabolismo , Celulasas/genética , Celulasas/metabolismo , Cromatografía Liquida , Fructosa/química , Glucano Endo-1,3-beta-D-Glucosidasa/genética , Glucano Endo-1,3-beta-D-Glucosidasa/metabolismo , Glicósido Hidrolasas/genética , Glicósido Hidrolasas/metabolismo , Saccharum/metabolismo , Análisis de Secuencia de ARN/métodos , Espectrometría de Masas en Tándem , Xilosidasas/genética , Xilosidasas/metabolismoRESUMEN
Carboxypeptidase A (CPA) is a metalloexopeptidase that catalyzes the hydrolysis of the peptide bonds that are adjacent to the C-terminal end of a polypeptide chain. The enzyme preferentially cleaves over C-terminal L-amino acids with aromatic or branched side chains. This is of main importance for food industry because it can be employed for manufacturing functional foods from different protein sources with reduced hydrophobic amino acid content for patients with deficiencies in the absorption or digestion of the corresponding amino acids. In that way, strategies for effective multipoint covalent immobilization of CPA metalloenzyme on chitosan beads have been developed. The study of the ability to produce several chemical modifications on chitosan molecules before, during and after its coagulation to form carrier beads lead in a protective effect of the polymer matrix. The chemical modification of chitosan through the use of an N-alkylation strategy produced the best derivatives. N-alkyl chitosan derivative beads with D-fructose presented values of 0.86 for immobilization yield, 314.6 IU g-1 bead for initial activity of biocatalyst and were 5675.64-fold more stable than the free enzyme at 55 °C. Results have shown that these derivatives would present a potential technological application in hydrolytic processes due to both their physical properties, such as low swelling capacity, reduced metal chelation ability and bulk mesoporosity, and increased operational stability when compared with soluble enzyme.
Asunto(s)
Carboxipeptidasas A/química , Quitosano/química , Enzimas Inmovilizadas/química , Biocatálisis , Estabilidad de Enzimas , Fructosa/química , CalorRESUMEN
The objective of this study was to evaluate the stability of 7 commonly used active pharmaceutical ingredients compounded in oral suspensions using an internationally used suspending vehicle (SyrSpend SF PH4): acetazolamide 25.0 mg/mL, baclofen 10.0 mg/mL, dipyridamole 10.0 mg/mL, mebeverine hydrochloride 10.0 mg/mL, propylthiouracil 5.0 mg/mL, quinidine sulfate 10.0 mg/mL, and topiramate 5.0 mg/mL. All suspensions were stored both at controlled refrigerated (2°C to 8°C) and room temperature (20°C to 25°C). Stability was assessed by measuring the percentage recovery at varying time points throughout a 90-day period. Active pharmaceutical ingredient quantification was performed by ultraviolet (UV) high-performance liquid chromatography, via a stability-indicating method. Given the percentage of recovery of the active pharmaceutical ingredients within the suspensions, the beyond-use date of the final products (active pharmaceutical ingredient + vehicle) was at least 90 days for all suspensions with regards to both temperatures. This suggests that SyrSpend SF PH4 is suitable for compounding active pharmaceutical ingredients from different pharmacological classes.
Asunto(s)
Composición de Medicamentos , Estabilidad de Medicamentos , Acetazolamida/química , Administración Oral , Baclofeno/química , Cromatografía Líquida de Alta Presión , Dipiridamol/química , Fructosa/análogos & derivados , Fructosa/química , Fenetilaminas/química , Propiltiouracilo/química , Quinidina/química , Suspensiones , TopiramatoRESUMEN
Lipases from Thermomyces lanuginosus (TLL) and Pseudomonas fluorescens (PFL) wereimmobilized on functionalized silica particles aiming their use in the synthesis of fructose oleate in a tert-butyl alcohol/water system. Silica particles were chemically modified with octyl (OS), octyl plus glutaraldehyde (OSGlu), octyl plus glyoxyl(OSGlx), and octyl plus epoxy groups(OSEpx). PFL was hyperactivated on all functionalized supports (more than 100% recovered activity) using low protein loading (1 mg/g), however, for TLL, this phenomenon was observed only using octyl-silica (OS). All prepared biocatalysts exhibited high stability by incubating in tert-butyl alcohol (half-lives around 50 h at 65 °C). The biocatalysts prepared using OS and OSGlu as supports showed excellent performance in the synthesis of fructose oleate. High estersynthesis was observed when a small amount of water (1%, v/v) was added to the organic phase, allowing an ester productivity until five times (0.88-0.96 g/L.h) higher than in the absence of water (0.18-0.34 g/L.h) under fixed enzyme concentration (0.51 IU/g of solvent). Maximum ester productivity (16.1-18.1 g/L.h) was achieved for 30 min of reaction catalyzed by immobilized lipases on OS and OSGlu at 8.4 IU/mL of solvent. Operational stability tests showed satisfactory stability after four consecutive cycles of reaction.
Asunto(s)
Enzimas Inmovilizadas , Fructosa/química , Lipasa/metabolismo , Ácido Oléico/síntesis química , Dióxido de Silicio , Biocatálisis , Estabilidad de Enzimas , Lipasa/química , Modelos Moleculares , Conformación Molecular , Solventes , AguaRESUMEN
D-tagatose is produced from D-galactose by the enzyme L-arabinose isomerase (L-AI) in a commercially viable bioprocess. An active and stable biocatalyst was obtained by modifying chitosan gel structure through reaction with TNBS, D-fructose or DMF, among others. This led to a significant improvement in L-AI immobilization via multipoint covalent attachment approach. Synthetized derivatives were compared with commercial supports such as Eupergit(®) C250L and glyoxal-agarose. The best chitosan derivative for L-AI immobilization was achieved by reacting 4 % (w/v) D-fructose with 3 % (w/v) chitosan at 50 °C for 4 h. When compared to the free enzyme, the glutaraldehyde-activated chitosan biocatalyst showed an apparent activity of 88.4 U g (gel) (-1) with a 211-fold stabilization factor while the glyoxal-agarose biocatalyst gave an apparent activity of 161.8 U g (gel) (-1) with an 85-fold stabilization factor. Hence, chitosan derivatives were comparable to commercial resins, thus becoming a viable low-cost strategy to obtain high active L-AI insolubilized derivatives.
Asunto(s)
Isomerasas Aldosa-Cetosa/química , Quitosano/química , Enterococcus faecium/enzimología , Enzimas Inmovilizadas/química , Microesferas , Isomerasas Aldosa-Cetosa/metabolismo , Enzimas Inmovilizadas/metabolismo , Fructosa/química , Glutaral/química , Concentración de Iones de Hidrógeno , Solubilidad , TemperaturaRESUMEN
Advanced glycation endproducts (AGE) are the result of post-translational changes to proteins, which ultimately compromise their structure and/or function. The identification of methods to prevent the formation of these compounds holds great promise in the development of alternative therapies for diseases such as diabetes. Plants used in traditional medicine are often rich sources of anti-glycation agents. Therefore, in this study, we investigated the anti-glycation activity of one such compound, Oncocalyxone A (Onco A). Using spectrofluorimetric techniques, we determined that Onco A inhibits AGE formation in a concentration-dependent manner. Its IC50 value (87.88 ± 3.08 µM) was almost two times lower than the standard anti-glycation compound aminoguanidine (184.68 ± 4.85 µM). The excellent anti-glycation activity of Onco A makes it an exciting candidate for the treatment of diseases associated with excessive accumulation of AGE. However, additional studies are necessary to identify its mechanism of action, as well as the in vivo response in suitable model organisms.
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Antraquinonas/química , Productos Finales de Glicación Avanzada/química , Animales , Antraquinonas/farmacología , Brasil , Bovinos , Relación Dosis-Respuesta a Droga , Evaluación Preclínica de Medicamentos , Fructosa/química , Glucosa/química , Glicosilación , Concentración 50 Inhibidora , Medicina Tradicional , Extractos Vegetales/química , Albúmina Sérica Bovina/química , Espectrometría de FluorescenciaRESUMEN
The literature indicates that red wine presents in its composition several substances that are beneficial to health. This study has investigated the antioxidant effects of Tannat red wine on oxidative stress induced by glucose and fructose in erythrocytes in vitro, with the purpose to determine some of its majoritarian phenolic compounds and its antioxidant capacity. Erythrocytes were incubated using different concentrations of glucose and fructose in the presence or absence of wine. From these erythrocytes were determined the production of thiobarbituric acid reactive species (TBARS), glucose consumption, and osmotic fragility. Moreover, quantification of total phenolic, gallic acid, caffeic acid, epicatechin, resveratrol, and DPPH scavenging activity in wine were also assessed. Red wine showed high levels of polyphenols analyzed, as well as high antioxidant potential. Erythrocytes incubated with glucose and fructose had an increase in lipid peroxidation and this was prevented by the addition of wine. The wine increased glucose uptake into erythrocytes and was able to decrease the osmotic fragility of erythrocytes incubated with fructose. Altogether, these results suggest that wine leads to a reduction of the oxidative stress induced by high concentrations of glucose and fructose.
Asunto(s)
Antioxidantes/farmacología , Eritrocitos/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Vino , Antioxidantes/química , Ácidos Cafeicos/química , Fructosa/química , Fructosa/metabolismo , Glucosa/química , Glucosa/metabolismo , Humanos , Peroxidación de Lípido/efectos de los fármacos , Fenoles/farmacología , Tiobarbitúricos/químicaRESUMEN
Sucrose from sugarcane is produced in abundance in Brazil, which provides an opportunity to manufacture other high-value products. Gluconic acid (GA) can be produced by multi-enzyme conversion of sucrose using the enzymes invertase, glucose oxidase, and catalase. In this process, one of the byproducts is fructose, which has many commercial applications. This work concerns the batch mode production of GA in an airlift reactor fed with sucrose as substrate. Evaluation was made of the influence of temperature and pH, as well as the thermal stability of the enzymes. Operational conditions of 40 °C and pH 6.0 were selected, based on the enzymatic activity profiles and the thermal stabilities. Under these conditions, the experimental data could be accurately described by kinetic models. The maximum yield of GA was achieved within 3.8 h, with total conversion of sucrose and glucose and a volumetric productivity of around 7.0 g L(-1) h(-1).
Asunto(s)
Reactores Biológicos , Gluconatos/química , Microbiología Industrial , Sacarosa/química , Catalasa/química , Cromatografía , Enzimas Inmovilizadas/química , Fructosa/química , Glucosa/química , Glucosa Oxidasa/química , Peróxido de Hidrógeno/química , Concentración de Iones de Hidrógeno , Temperatura , beta-Fructofuranosidasa/químicaRESUMEN
Three α-ketoaldehydes, potentially present in high fructose agave syrups (HFASs) as intermediates of the Maillard reaction, were determined. A previously reported HPLC-FLD procedure based on pre-column derivatisation with 4-methoxy-o-phenylenediamine was adopted, yielding the method quantification limits 0.11 mg/kg, 0.10mg/kg, 0.09 mg/kg for glyoxal, methylglyoxal (MGo) and diacetyl, respectively. The obtained results revealed high concentrations of methylglyoxal in HFASs (average 102 ± 91 mg/kg, range 15.6-315 mg/kg) as compared to commercial Mexican bee honeys or corn syrups. Hydrogen peroxide was generated in all HFASs upon dilution, yet to less extent than in bee honeys. HFASs presented bacteriostatic activity against Bacillus subtilis and Escherichia coli; catalase addition had minimum effect on the assay results in syrups with elevated MGo. Principal component analysis revealed direct association between growth inhibition and MGo. It is concluded that elevated concentration of MGo in HFASs is at least in part responsible for their non-peroxide bacteriostatic activity.
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Agave/química , Cromatografía Líquida de Alta Presión/métodos , Fructosa/química , Miel/análisis , Animales , AbejasRESUMEN
Acrylamide (AA) is known as a neurotoxin in humans and it is classified as a probable human carcinogen by the International Agency of Research on Cancer. AA is produced as by-product of the Maillard reaction in starchy foods processed at high temperatures (>120 °C). This review includes the investigation of AA precursors, mechanisms of AA formation and AA mitigation technologies in potato, cereal and coffee products. Additionally, most relevant issues of AA risk assessment are discussed. New technologies tested from laboratory to industrial scale face, as a major challenge, the reduction of AA content of browned food, while still maintaining its attractive organoleptic properties. Reducing sugars such as glucose and fructose are the major contributors to AA in potato-based products. On the other hand, the limiting substrate of AA formation in cereals and coffee is the free amino acid asparagine. For some products the addition of glycine or asparaginase reduces AA formation during baking. Since, for potatoes, the limiting substrate is reducing sugars, increases in sugar content in potatoes during storage then introduce some difficulties and potentially quite large variations in the AA content of the final product. Sugars in potatoes may be reduced by blanching. Levels of AA in different foods show large variations and no general upper limit is easily applicable, since some formation will always occur. Current policy is that practical measures should be taken voluntarily to reduce AA formation in vulnerable foods since AA is considered a health risk at the concentrations found in foods.
Asunto(s)
Acrilamida/química , Acrilamida/toxicidad , Dieta/efectos adversos , Acrilamida/análisis , Animales , Asparaginasa/administración & dosificación , Asparagina/metabolismo , Carcinógenos , Café/química , Grano Comestible/química , Manipulación de Alimentos/métodos , Fructosa/análisis , Fructosa/química , Glucosa/análisis , Glucosa/química , Calor , Humanos , Reacción de Maillard , Sistema Nervioso/efectos de los fármacos , Medición de Riesgo , Solanum tuberosum/química , Almidón/químicaRESUMEN
Invertase from Saccharomyces cerevisiae was immobilized on agarose beads, activated with various groups (glyoxyl, MANAE or glutaraldehyde), and on some commercial epoxy supports (Eupergit and Sepabeads). Very active and stable invertase derivatives were produced by the adsorption of the enzyme on MANAE-agarose, MANAE-agarose treated with glutaraldhyde and glutaraldehyde-agarose supports. At pH 5.0, these derivatives retained full activity after 24h at 40 ºC and 50 ºC. When assayed at 40 °C and 50 °C, with the pH adjusted to 7.0, the invertase-MANAE-agarose derivative treated with glutaraldehyde retained 80% of the initial activity. Recovered activities of the derivatives produced with MANAE, MANAE treated with glutaraldehyde and glutaraldehyde alone were 73.5%, 44.4% and 36.8%, respectively. These three preparations were successfully employed to produce glucose and fructose in 3 cycles of sucrose hydrolysis.
Invertase de Saccharomyces cerevisiae foi imobilizada em agarose ativada com diferentes grupos (glioxil, MANAE ou glutaraldeído) e suportes epóxidos comerciais (Eupergit e Sepabeads). Derivados de invertase ativos e estabilizados foram produzidos pela adsorção da enzima em suportes MANAE-agarose, MANAE-agarose tratado com glutaraldeído e glutaraldeído-agarose. Em pH 5,0 estes derivados retiveram total atividade até 24h a 40 ºC e 50 ºC. Quando os ensaios foram a 40 °C e 50 °C com o pH alterado para 7,0, o derivado invertase-MANAE-agarose tratado com glutaraldeído apresentou 80% da atividade inicial. As atividades recuperadas dos derivados foram 73,5%, 44,4% e 36,8%, respectivamente para MANAE, MANAE tratado com glutaraldeído e glutaraldeído. Essas três preparações foram empregadas com sucesso em 3 ciclos de hidrólise da sacarose para produzir glicose e frutose.
Asunto(s)
Fructosa/química , Glucosa/química , Saccharomyces cerevisiae/químicaRESUMEN
It is estimated that at least 100 million people worldwide will suffer from epilepsy at some point in their lives. This neurological disorder induces brain death due to the excessive liberation of glutamate, which activates the postsynaptic N-methyl-D-aspartic acid (NMDA) receptors, which in turn cause the reuptake of intracellular calcium (excitotoxicity). This excitotoxicity elicits a series of events leading to nitric oxide synthase (NOS) activation and the generation of reactive oxygen species (ROS). Several studies in experimental models and in humans have demonstrated that certain antiepileptic drugs (AEDs) exhibit antioxidant effects by modulating the activity of various enzymes associated with this type of stress. Considering the above-mentioned data, we aimed to compile evidence elucidating how AEDs such as valproic acid (VPA), oxcarbazepine (OXC), and topiramate (TPM) modulate oxidative stress.