A new process combining adsorption and enzyme reaction for producing higher-fructose syrup

A process for producing a higher-fructose syrup containing more than 50% fructose was developed that involves a new system combining selective adsorption of fructose and an immobilized glucose isomerase reaction. Continuous countercurrent contact of the liquid stream with the solid adsorbent is simulated by advancing adsorption columns against the fixed inlets and outlet of liquid streams without actual movement of the solid adsorbent, while the immobilized enzyme reactors are stationary. Two mathematical models, an intermittent moving-bed and a continuous moving-bed model, are presented for calculation the concentration profiles of glucose and fructose in the system. The validity of the models is experimentally confirmed, and a criterion for good production in the system is presented. This system requires less desorbent than a process using a fixed-bed adsorber and a simulated moving-bed process to produce the syrup with 45-65% fructose content, the level desired in food manufacture.     

Equilibrium and a two-stage batch adsorber design for reactive or disperse dye removal to minimize adsorbent amount

The adsorption of a reactive dye (Reactive Yellow K-4G) and a disperse dye (Disperse yellow brown S-2RFL) onto polyepicholorohydrin-dimethylamine (EPIDMA) cationic polymer modified bentonite (EPIDMA-bentonite) in batch adsorber was studied, respectively. Two equilibrium models, the Langmuir and Freundlich models were selected to follow the adsorption process. It was shown that the equilibrium experimental data for reactive dye adsorption could be well described by the Freundlich model, but for disperse dye the Langmuir model could be better. Based on the well correlated adsorption isotherm, an adsorption process design model was developed for the design of a two-stage batch adsorber to predict the minimum amount of adsorbent to achieve a specified percentage of dye removal at a given volume of wastewater effluents. The adsorption process design analysis indicated that compared with the single-stage batch adsorption, the two-stage process could significantly save adsorbent to meet the higher demands of dye removal efficiency.     

Glutamate inhibits chondral mineralization through apoptotic cell death mediated by retrograde operation of the cystine/glutamate antiporter

Although we have previously demonstrated the functional significance of excitatory amino acid transporters as well as glutamate (Glu) receptors (GluRs) expressed by chondrocytes, little attention has been paid to the possible expression of the cystine/Glu antiporter responsible for the bi-directional transmembrane transport of Glu in chondrocytes to date. In organotypic cultured mouse embryonic metatarsals isolated before vascularization, the chondral mineralization was significantly decreased in the presence of Glu at a high concentration. Apoptotic cells were detected within the late proliferating and prehypertrophic chondrocytic layers in metatarsals cultured in the presence of Glu. A group III metabotropic GluR (mGluR) antagonist partially, but significantly, prevented the inhibition of mineralization by Glu in metatarsals without affecting the number of apoptotic cells. Both decreased mineralization and apoptosis by Glu were significantly prevented by the addition of the cystine/Glu antiporter inhibitor homocysteic acid, as well as reduced glutathione (GSH) and cystine. Expression of mRNA for xCT and 4F2hc subunits, which are components of the cystine/Glu antiporter, was seen in both cultured mouse metatarsals and rat costal chondrocytes. In chondrocytes cultured with Glu, a significant decrease was seen in intracellular GSH levels, together with increases in the number of apoptotic cells and the level of intracellular reactive oxygen species. These results suggest that Glu could regulate chondrogenic differentiation toward mineralization through a mechanism associated with apoptosis mediated by the depletion of intracellular GSH after the retrograde operation of the cystine/Glu antiporter, in addition to the activation of group III mGluR, in chondrocytes.     

Glutathione-induced inhibition of Na+-independent and -dependent bindings of L-[3H]glutamate in rat brain

Reduced glutathione (GSH, 10(-7)-10(-3) M) was found to exert a profound suppressive action on the Na+-independent and -dependent bindings of L-[3H]glutamic acid (Glu) in a temperature-independent manner. Similarly significant reduction of the bindings resulted from the addition of oxidized glutathione (GSSG). Scatchard analysis revealed that GSH as well as GSSG invariably decreased the affinity of the binding sites for [3H]Glu without significantly affecting the number of the binding sites. These results suggest that GSH (GSSG) may in part participate in the synaptic transmission at central Glu neurons through interaction with the receptors and/or the uptake sites for Glu.     

In situ fabrication of a microfluidic device for immobilised metal affinity sensing

In this work a novel microfluidic device was constructed in situ containing the smallest microscopic co-polymeric immobilised metal affinity (IMA) adsorbent yet documented. This device has for the first time allowed the microlitre scale chromatographic assay of histidine-tagged proteins in a biological sample. To enable this approach, rather than using a high capacity commercial packed bed column which requires large sample volumes and would be susceptible to occlusion by cell debris, a microgram capacity co-polymeric chromatographic substrate suitable for analytical applications was fabricated within a microfluidic channel. This porous co-polymeric IMA micro-chromatographic element, only 27μl in volume, was assessed for the analytical capture of two different histidine-tagged recombinant fusion proteins. The micro-chromatographic adsorber was fabricated in situ by photo-polymerising an iminodiacetic acid (IDA) functionalised polymer matrix around a template of fused 100μm diameter NH(4)Cl particles entirely within the microfluidic channel and then etching away the salt with water to form a network of interconnected voids. The surface of the micro-chromatographic adsorber was chemically functionalised with a chelating agent and loaded with Cu(2+) ions. FTIR and NMR analysis verified the presence of the chelating agent on the adsorbent surface and its Cu(2+) ion binding capacity was determined to be 2.4μmol Cu(2+) (ml of adsorbent)(-1). Micro-scale equilibrium adsorption studies using the two different histidine-tagged proteins, LacI-His(6)-GFP and α-Synuclein-His(8)-YFP, were carried out and the protein binding capacity of the adsorbent was determined to be 0.370 and 0.802mg(g of adsorbent)(-1), respectively. The dynamic binding capacity was determined at four different flow rates and found to be comparable to the equilibrium binding capacity at low flow rates. The sensing platform was also used to adsorb LacI-His(6)-GFP protein from crude cell lysate. During adsorption, laser scanning confocal microscopy identified locations within the adsorbent where protein adsorption and desorption occurred. The findings indicate that minimal channelling, selective product capture and near quantitative elution of the captured (adsorbed) product could be achieved, supporting the application of this new device as a high-throughput process analytical tool (PAT) for the in-process monitoring of histidine-tagged proteins in manufacturing.     

Glutamate-64, a newly identified residue of the functionally conserved electron-sharing network contributes to catalysis and structural integrity of glutathione transferases

In Anopheles dirus glutathione transferase D3-3, position 64 is occupied by a functionally conserved glutamate residue, which interacts directly with the gamma-glutamate moiety of GSH (glutathione) as part of an electron-sharing network present in all soluble GSTs (glutathione transferases). Primary sequence alignment of all GST classes suggests that Glu64 is one of a few residues that is functionally conserved in the GST superfamily. Available crystal structures as well as consideration of the property of the equivalent residue at position 64, acidic or polar, suggest that the GST electron-sharing motif can be divided into two types. Electrostatic interaction between the GSH glutamyl and carboxylic Glu64, as well as with Arg66 and Asp100, was observed to extend the electron-sharing motif identified previously. Glu64 contributes to the catalytic function of this motif and the 'base-assisted deprotonation' that are essential for GSH ionization during catalysis. Moreover, this residue also appears to affect multiple steps in the enzyme catalytic strategy, including binding of GSH, nucleophilic attack by thiolate at the electrophilic centre and product formation, probably through active-site packing effects. Replacement with non-functionally-conserved amino acids alters initial packing or folding by favouring aggregation during heterologous expression. Thermodynamic and reactivation in vitro analysis indicated that Glu64 also contributes to the initial folding pathway and overall structural stability. Therefore Glu64 also appears to impact upon catalysis through roles in both initial folding and structural maintenance.     

Effect of cysteine,glutamate and glycine supplementation to in vitro fertilization medium during bovine early embryo development

Glutathione (GSH) is an antioxidant synthesized from three constitutive amino acids (CAA): cysteine (Cys), glycine (Gly) and glutamate (Glu). Glutathione plays an important role in oocyte maturation, fertilization and early embryo development. This study aimed to investigate the effect of Cys (0.6 mM), Gly (0.6 mM) and Glu (0.9 mM) supplementation during in vitro fertilization (IVF) of cattle oocytes. In a Pilot Experiment, de novo synthesis of GSH in bovine zygote was evaluated using a modified TALP medium prepared without MEM-essential and MEM-non-essential amino acids (mTALP): mTALP + CAA (constitutive amino acids); mTALP + CAA+5 mMBSO (buthionine sulfoximide); mTALP + Cys + Gly; mTALP + Cys + Glu and mTALP + Gly + Glu. This evidence led us to investigate the impact of CAA supplementation to TALP medium (with essential and non-essential amino acids) on zygote viability, lipid peroxidation, total intracellular GSH content (include reduced and oxidized form; GSH-GSSG), pronuclear formation in zygotes and subsequent embryo development. IVF media contained a) TALP; b) TALP + Cys + Gly + Glu (TALP + CAA); c) TALP + Cys + Gly; d) TALP + Cys + Glu; e) TALP + Gly + Glu, were used. Total GSH-GSSG concentration was increased in TALP, TALP + CAA, and TALP + Cys + Gly. The viability of zygote was similar among treatments. Lipid peroxidation was increased in zygote fertilized with TALP + Cys + Gly; TALP + Cys + Glu; TALP + Gly + Glu and TALP + CAA. The percentage of penetrated oocytes decreased in TALP + CAA and TALP + Cys + Gly. The cleavage rate was lower in TALP + CAA and TALP + Gly + Glu. The percentage of embryos developing to the blastocyst stage was lower in TALP + Cys + Glu and TALP + CAA. In conclusion, we have demonstrated the synthesis of GSH during IVF. However, Cys, Gly and Glu supplementation to TALP medium had negative effects on embryonic development.     

Removal of herbicide paraquat from an aqueous solution by adsorption onto spent and treated diatomaceous earth

A spent diatomaceous earth from the beer brewery has been tentatively activated by sodium hydroxide at about 100 degrees C. The resulting product was used as a novel adsorbent for the adsorption of herbicide paraquat from an aqueous solution in a continuously stirred adsorber and batch flasks, respectively. The results showed that the adsorption process could be well described by the pseudo-second-order reaction model. From the view of the negatively charged surface of diatomaceous earth and cationic property of paraquat, the results were also reasonable to be explained by physical adsorption in the ion-exchange process under the effects of pH and temperature. Further, it was found that the Freundlich model appeared to fit the isotherm data better than the Langmuir model.     

Suppression by glutamate of proliferative activity through glutathione depletion mediated by the cystine/glutamate antiporter in mesenchymal C3H10T1/2 stem cells

Although previous studies including ours have demonstrated the functional expression of different glutamate (Glu) signaling machineries such as Glu receptors (GluRs) and transporters in osteoblasts and chondrocytes, little attention has been paid to the role of Glu in their ancestral mesenchymal stem cells to date. In the present study, we have evaluated the possible functionality of Glu in cultured mouse mesenchymal stem cell line C3H10T1/2 cells endowed to proliferate for the self-renewal and to differentiate toward osteoblast, chondrocyte, adipocyte, and myocyte lineages. Expression of mRNA was for the first time shown with the cystine/Glu antiporter composed of xCT and 4F2hc subunits, in addition to particular excitatory amino acid transporter (EAAT) isoforms and ionotropic GluRs, in undifferentiated C3H10T1/2 cells. Glu significantly suppressed the proliferation activity at a concentration over 500 microM without inducing cell death or differentiation, while the suppression occurred in a manner sensitive to the prevention by cystine and reduced glutathione (GSH), but not by EAAT inhibitors. A significant decrease was seen in intracellular GSH levels in C3H10T1/2 cells cultured with Glu, whereas the cellular proliferation activity was drastically decreased by the addition of the GSH depleter cyclohexene-1-one and the GSH biosynthesis inhibitor L-buthionine-[S,R]-sulfoximine, respectively. Transient overexpression of both xCT and 4F2hc subunits led to an increased basal proliferative activity in C3H10T1/2 cells. These results suggest that Glu could suppress the cellular proliferation toward self-renewal through a mechanism associated with the depletion of intracellular GSH after promoting the retrograde operation of the cystine/Glu antiporter in C3H10T1/2 cells.     

Glutamate modulation of human lymphocyte growth: in vitro studies

Peripheral blood mononuclear cell (PBMC) proliferation induced by phytohemagglutinin, or by anti-CD3 alone or plus anti-CD28 monoclonal antibodies (mAb) was inhibited by glutamate (Glu) in a concentration-dependent manner. This inhibition was not reproduced by selective ionotropic Glu receptor agonists, whereas it was potentiated by l-buthionine-(S,R)-sulfoximine, which depletes glutathione (GSH) stores, and counteracted by 2-mercaptoethanol, a preserver of cell thiols. The inhibitory effects of Glu were related to depletion of intracellular GSH stores, since it decreased GSH levels in a concentration-dependent manner. Furthermore, Glu modulated cytokine secretion by anti-CD3 mAb activated PBMC: it increased IFN-gamma (+44.3+/-8.2%) and IL-10 (+31.6+/-9.7%) secretion, whereas that of IL-2, IL-4, IL-5, and TNF-alpha was not affected. These data suggest that high levels of Glu, which can be reached in damaged tissues, modulate lymphocyte responses to activating stimuli by favouring polarization of the T helper effector response.     

A gamma-glutamyl transpeptidase-independent pathway of glutathione catabolism to glutamate via 5-oxoproline in Arabidopsis

The degradation pathway of glutathione (GSH) in plants is not well understood. In mammals, GSH is predominantly metabolized through the γ-glutamyl cycle, where GSH is degraded by the sequential reaction of γ-glutamyl transpeptidase (GGT), γ-glutamyl cyclotransferase, and 5-oxoprolinase to yield glutamate (Glu) and dipeptides that are subject to peptidase action. In this study, we examined if GSH is degraded through the same pathway in Arabidopsis (Arabidopsis thaliana) as occurs in mammals. In Arabidopsis, the oxoprolinase knockout mutants (oxp1-1 and oxp1-2) accumulate more 5-oxoproline (5OP) and less Glu than wild-type plants, suggesting substantial metabolite flux though 5OP and that 5OP is a major contributor to Glu steady-state levels. In the ggt1-1/ggt4-1/oxp1-1 triple mutant with no GGT activity in any organs except young siliques, the 5OP concentration in leaves was not different from that in oxp1-1, suggesting that GGTs are not major contributors to 5OP production in Arabidopsis. 5OP formation strongly tracked the level of GSH in Arabidopsis plants, suggesting that GSH is the precursor of 5OP in a GGT-independent reaction. Kinetics analysis suggests that γ-glutamyl cyclotransferase is the major source of GSH degradation and 5OP formation in Arabidopsis. This discovery led us to propose a new pathway for GSH turnover in plants where GSH is converted to 5OP and then to Glu by the combined action of γ-glutamyl cyclotransferase and 5-oxoprolinase in the cytoplasm.     

Metabolic requirements associated with GSH synthesis during in vitro maturation of cattle oocytes

Glutathione (GSH) concentration increases in bovine oocytes during in vitro maturation (IVM). The constitutive amino acids involved in GSH synthesis are glycine (Gly), glutamate (Glu) and cysteine (Cys). The present study was conducted to investigate the effect of the availability of glucose, Cys, Gly and Glu on GSH synthesis during IVM. The effect of the amino acid serine (Ser) on intracellular reduced/oxidized glutathione (GSH/GSSG) content in both oocytes and cumulus cells was also studied. Cumulus-oocyte complexes (COC) of cattle obtained from ovaries collected from an abattoir were matured in synthetic oviduct fluid (SOF) medium containing 8 mg/ml bovine serum albumin-fatty acid-free (BSA-FAF), 10 microg/ml LH, 1 microg/ml porcine FSH (pFSH) and 1 microg/ml 17 beta-estradiol (17beta-E2). GSH/GSSG content was measured using a double-beam spectrophotometer. The COC were cultured in SOF supplemented with 1.5mM or 5.6mM glucose (Exp. 1); with or without Cys+Glu+Gly (Exp. 2); with the omission of one constitutive GSH amino acid (Exp. 3); with 0.6mM Cys or Cys+Ser (Exp. 4). The developmental capacity of oocytes matured in IVM medium supplemented with Cys and the cell number per blastocyst were determined (Exp. 5). The results reported here indicate (1) no differences in the intracellular GSH/GSSG content at any glucose concentrations. Also, cumulus cell number per COC did not differ either before or after IVM (Exp. 1). (2) Glutathione content in oocytes matured in SOF alone were significantly different from oocytes incubated with SOF supplemented with Cys+Glu+Gly (Exp. 2). (3) Addition of Cys to maturation medium, either with or without Gly and Glu supplementation resulted in an increase of GSH/GSSG content. However, when Cys was omitted from the IVM medium intracellular GSH in oocytes or cumulus cells was less but not significantly altered compared to SOF alone (Exp. 3). (4) Glutathione content in both oocytes and cumulus cells was significantly reduced by incubation with 5mM Ser (Exp.4). (5) There was a significant increase in cleavage and blastocyst rates when Cys was added to maturation medium. In contrast, the cleavage, morula and blastocyst rates were significantly different when 5mM Ser was added to maturation media. There was also a significant difference in mean cell number per blastocyst, obtained from oocytes matured with 5mM Ser (Exp. 5). This study provides evidence that optimal embryo development in vitro is partially dependent on the presence of precursor amino acids for intracellular GSH production. Moreover, the availability of Cys might be a critical factor for GSH synthesis during IVM in cattle oocytes. Greater Ser concentration in IVM medium altered "normal" intracellular GSH in both oocytes and cumulus cells with negative consequences for subsequent developmental capacity.     

Development of a polishing step using a hydrophobic interaction membrane adsorber with a PER.C6®‐derived recombinant antibody

Membrane chromatography has already proven to be a powerful alternative to polishing columns in flow‐through mode for contaminant removal. As flow‐through utilization has expanded, membrane chromatography applications have included the capturing of large molecules, including proteins such as IgGs. Such bind‐and‐elute applications imply the demand for high binding capacity and larger membrane surface areas as compared to flow‐through applications. Given these considerations, a new Sartobind Phenyl? membrane adsorber was developed for large‐scale purification of biomolecules based on hydrophobic interaction chromatography (HIC) principles. The new hydrophobic membrane adsorber combines the advantages of membrane chromatography—virtually no diffusion limitation and shorter processing time—with high binding capacity for proteins comparable to that of conventional HIC resins as well as excellent resolution. Results from these studies confirmed the capability of HIC membrane adsorber to purify therapeutic proteins with high dynamic binding capacities in the range of 20 mg‐MAb/cm³‐membrane and excellent impurity reduction. In addition the HIC phenyl membrane adsorber can operate at five‐ to ten‐fold lower residence time when compared to column chromatography. A bind/elute purification step using the HIC membrane adsorber was developed for a recombinant monoclonal antibody produced using the PER.C6® cell line. Loading and elution conditions were optimized using statistical design of experiments. Scale‐up is further discussed, and the performance of the membrane adsorber is compared to a traditional HIC resin used in column chromatography. Biotechnol. Bioeng. 2010; 105: 296–305. © 2009 Wiley Periodicals, Inc.     

Simulated moving-bed chromatography and its application to chirotechnology

The increased awareness of the differences in biological activity of the two enantiomers of a chiral drug has raised the demand for enantiomerically pure products, particularly in the pharmaceutical industry. Simulated moving-bed chromatography can be used for the separation of the two enantiomers of a chiral molecule, which is feasible at all production scales, from laboratory to pilot to production plant. The use of non-enantioselective synthesis of racemic mixtures and simulated moving-bed enantiomer separation might make the development process of a new chiral drug substantially shorter and cheaper.     

Effects on GSH synthesis in Chinese cabbage when the culturing solution is supplemented with ammonium sulfate or the constituent amino acids for glutathione

We examined the effects of the constituent amino acids for glutathione (GSH) — glutamate (Glu), cysteine (Cys), and glycine (Gly) — on GSH synthesis in Chinese cabbage seedlings. Glu, Cys, and Gly were applied simultaneously (100 mg L^-1) to the culture solution for 2 d. When compared with the control, GSH concentrations were increased by 2.1-fold (640.4 nmol g^-1 FW) and 1.5-fold (416.4 nmol g^-1 FW) in the first leaf and the roots, respectively. Of all the free amino acids, the non-essentials, including Glu, Cys and Gly, occupied 95.5% (shoots) and 81.9% (roots) of the total. Cys supplements greatly enhanced the GSH concentration in the roots; application of 100 mg L^-1 increased the level by 7-fold over the control. The activity of GSH synthetase was higher in the roots than in the leaf, whereas that of y-glutamylcysteine synthetase was higher in the leaf.     

Simulated diving after heat stress potentiates the induction of heat shock protein 70 and elevates glutathione in human endothelial cells

Heat stress prior to diving has been shown to confer protection against endothelial damage due to decompression sickness. Several lines of evidence indicate a relation between such protection and the heat shock protein (HSP)70 and HSP90 and the major cellular red-ox determinant, glutathione (GSH). The present study has used human endothelial cells as a model system to investigate how heat stress and simulated diving affect these central cellular defense molecules. The results demonstrated for the first time that a simulated dive at 2.6 MPa (26 bar) had a potentiating effect on the heat-induced expression of HSP70, increasing the HSP70 concentration on average 54 times above control level. In contrast, a simulated dive had no significant potentiating effect on the HSP90 level, which might be due to the higher baseline level of HSP90. Both 2 and 24-h dive had similar effects on the HSP70 and HSP90, suggesting that the observed effects were independent of duration of the dive. The rapid HSP response following a 2-h dive with a decompression time of 5 min might suggest that the effects were due to compression or pressure per se rather than decompression and may involve posttranslational processing of HSP. The exposure order seemed to be critical for the HSP70 response supporting the suggestion that the potentiating effect of dive was not due to de novo synthesis of HSP70. Neither heat shock nor a simulated dive had any significant effect on the intracellular GSH level while a heat shock and a subsequent dive increased the total GSH level approximately 62%. Neither of these conditions seemed to have any effect on the GSH red-ox status.     

ATP and GSH dependence of MRP1-mediated outward translocation of phospholipid analogs in the human erythrocyte membrane

The active outward translocation of phospholipid analogues from the inner to the outer membrane leaflet of human erythrocytes by the multi-drug resistance protein MRP1 (ABCC1) depends on intracellular reduced glutathione (GSH). Entrapment of ATP and increasing amounts of GSH inside resealed ghosts prepared from erythrocytes resulted in an up to six-fold increase of the translocation rate. Entrapped oxidized glutathione (GSSG) acted inhibitory but produced stimulation after addition of the disulphide-reducing reagent dithioerythritol. Modification of GSH by esterification of the C-terminal carboxylate of Gly, removal of the N-terminal Glu or substitution of the SH group by an anionic S-dicarboxyethyl or sulphonate group abolished stimulation. The effect of S-alkylation of GSH depended on the length of the alkyl group. S-methyl GSH was somewhat more effective than GSH, but maximal stimulation was similar. S-butyl GSH acted poorly stimulatory while S-hexyl GSH was essentially ineffective. Analyses of the kinetic data of translocation revealed K(m) values for GSH and methyl-GSH of respectively 7.4 +/- 2.4 and 4.9 +/- 1.1 mmol l(-1). At high GSH levels and defined constant ATP levels using an ATP-regenerating system, the Km for ATP of the outward translocation was 0.16 +/- 0.02 mmol l(-1). In the same system lacking GSH, the Km for ATP of the inward translocation by the aminophospholipid flippase was 0.53 +/- 0.23 mmol l(-1).     

Adsorption of cationic dye from aqueous solutions by date pits: Equilibrium,kinetic, thermodynamic studies,and batch adsorber design

The retention profile of methylene blue from aqueous solutions onto the solid adsorbent date pits has been investigated in a batch system. The characterization and adsorption efficiency for methylene blue was evaluated using date pits. Fourier Transform Infra-Red, Scanning Electron Microscope, Brunauer–Emmett–Teller analysis were performed to determine the characteristics of the material. The effect of contact time, initial dye concentration, adsorbent dosage, temperature, and solution pH were investigated. The adsorption was found to increase with increasing time, decreasing concentration of dye, decreasing temperature and increasing dosage up to equilibrium values which was 20 min, 25°C, and 0.1 g adsorbent, respectively. The adsorption was favorable at high and low pH (pH 3, pH 7). The adsorption equilibrium data were best fitted by Freundlich isotherm. The adsorption kinetics was found to follow the pseudo second order kinetic model. Thermodynamic parameters such as free energy, enthalpy, and entropy were calculated and found to be ?4.6 kJ/mole, ?7.9 kJ/mole, and ?11.8 kJ/mole, respectively. The thermodynamic parameters of the uptake of methylene blue onto the date pits indicated that, the process is exothermic and proceeds spontaneously at low temperature. A single stage batch adsorber was designed for adsorption of methylene blue by Date Pits based on optimum isotherm.     

Formation mechanism of cross‐linking Maillard compounds in peptide–xylose systems

The formation mechanism of Maillard peptides was explored in Maillard reaction through diglycine/glutathione(GSH)/(Cys‐Glu‐Lys‐His‐Ile‐Met)–xlyose systems by heating at 120 °C for 30–120 min. Maximum fluorescence intensity of Maillard reaction products (MRPs) with an emission wavelength of 420~430 nm in all systems was observed, and the intensity values were proportional to the heating time. Taken diglycine/GSH–[¹³C₅]xylose systems as a control, it was proposed that the compounds with high m/z values of 379 and 616 have the high molecular weight (HMW) products formed by cross‐linking of peptides and sugar. In (Cys‐Glu‐Lys‐His‐Ile‐Met)–xylose system, the m/z value of HMW MRPs was not observed, which might be due to the weak signals of these products. According to the results of gel permeation chromatography, HMW MRPs were formed by Maillard reaction, especially in (Cys‐Glu‐Lys‐His‐Ile‐Met)–xylose system, the percentage of Maillard peptides reached 52.90%. It was concluded that Maillard peptides can be prepared through the cross‐linking of sugar and small peptides with a certain MW range. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.