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Glucose Release (glucose + release)
Selected AbstractsEffects of cellulase and xylanase enzymes on the deconstruction of solids from pretreatment of poplar by leading technologiesBIOTECHNOLOGY PROGRESS, Issue 2 2009Rajeev Kumar Abstract Comparative data is presented on glucose and xylose release for enzymatic hydrolysis of solids produced by pretreatment of poplar wood by ammonia fiber expansion (AFEX), ammonia recycled percolation (ARP), controlled pH, dilute acid, flowthrough (FT), lime, and sulfur dioxide (SO2) technologies. Sugar solubilization was measured for times of up to 72 h using cellulase supplemented with ,-glucosidase at an activity ratio of 1:2, respectively, at combined protein mass loadings of 5.8,116 mg/g of glucan in poplar wood prior to pretreatment. In addition, the enzyme cocktail was augmented with up to 11.0 g of xylanase protein per gram of cellulase protein at combined cellulase and ,-glucosidase mass loadings of 14.5 and 29.0 mg protein (about 7.5 and 15 FPU, respectively)/g of original potential glucose to evaluate cellulase,xylanase interactions. All pretreated poplar solids required high protein loadings to realize good sugar yields via enzymatic hydrolysis, and performance tended to be better for low pH pretreatments by dilute sulfuric acid and sulfur dioxide, possibly due to higher xylose removal. Glucose release increased nearly linearly with residual xylose removal by enzymes for all pretreatments, xylanase leverage on glucan removal decreased at high cellulase loadings. Washing the solids improved digestion for all pretreatments and was particularly beneficial for controlled pH pretreatment. Furthermore, incubation of pretreated solids with BSA, Tween 20, or PEG6000 prior to adding enzymes enhanced yields, but the effectiveness of these additives varied with the type of pretreatment. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Tunable transport of glucose through ionically-crosslinked alginate gels: Effect of alginate and calcium concentrationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Mari-Kate E. McEntee Abstract Alginate beads have numerous biomedical applications, ranging from cell encapsulation to drug release. The present study focuses on the controlled release of glucose from calcium-alginate beads. The effects of alginate concentrations (1,6 wt %) and calcium chloride concentrations (0.1,1.0M) on glucose release from beads were examined. It was found that the time required for complete glucose release from beads could be tuned from 15 min to over 2 h, simply by varying alginate and calcium chloride concentrations in beads. For calcium-alginate beads with sodium alginate concentrations of 1,4 wt %, higher sodium alginate concentrations lead to more prolonged release of glucose and thus a smaller value of a rate constant k, a parameter shown to be proportional to the diffusion coefficient of glucose in the alginate gel. For beads with sodium alginate concentrations of 4,6 wt %, there was no statistically significant difference in k values, indicating a lower limit for glucose release from calcium-alginate beads. Similarly, higher calcium chloride concentrations appear to extend glucose release, however, no conclusive trend can be drawn from the data. In a 50 : 50 mixture of calcium-alginate beads of two different alginate concentrations (1 and 4 wt %), glucose release showed a two-step profile over the time range of 20,50 min, indicating that the pattern and time of glucose release from beads can be tuned by making combinations of beads with varying alginate and/or calcium chloride concentrations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Studies on the effects of lactate transport inhibition, pyruvate, glucose and glutamine on amino acid, lactate and glucose release from the ischemic rat cerebral cortexJOURNAL OF NEUROCHEMISTRY, Issue 1 2001J. W. Phillis A rat four vessel occlusion model was utilized to examine the effects of ischemia/reperfusion on cortical window superfusate levels of amino acids, glucose, and lactate. Superfusate aspartate, glutamate, phosphoethanolamine, taurine, and GABA were significantly elevated by cerebral ischemia, then declined during reperfusion. Other amino acids were affected to a lesser degree. Superfusate lactate rose slightly during the initial ischemic period, declined during continued cerebral ischemia and then was greatly elevated during reperfusion. Superfusate glucose levels declined to near zero levels during ischemia and then rebounded beyond basal levels during the reperfusion period. Inhibition of neuronal lactate uptake with ,-cyano-4-hydroxycinnamate dramatically elevated superfusate lactate levels, enhanced the ischemia/reperfusion evoked release of aspartate but reduced glutamine levels. Topical application of an alternative metabolic fuel, glutamine, had a dose dependent effect. Glutamine (1 mm) elevated basal superfusate glucose levels, diminished the decline in glucose during ischemia, and accelerated its recovery during reperfusion. Lactate levels were elevated during ischemia and reperfusion. These effects were not evident at 5 mm glutamine. At both concentrations, glutamine significantly elevated the superfusate levels of glutamate. Topical application of sodium pyruvate (20 mm) significantly attenuated the decline in superfusate glucose during ischemia and enhanced the levels of both glucose and lactate during reperfusion. However, it had little effect on the ischemia-evoked accumulation of amino acids. Topical application of glucose (450 mg/dL) significantly elevated basal superfusate levels of lactate, which continued to be elevated during both ischemia and reperfusion. The ischemia-evoked accumulations of aspartate, glutamate, taurine and GABA were all significantly depressed by glucose, while phosphoethanolamine levels were elevated. These results support the role of lactate in neuronal metabolism during ischemia/reperfusion. Both glucose and glutamine were also used as energy substrates. In contrast, sodium pyruvate does not appear to be as effectively utilized by the ischemic/reperfused rat brain since it did not reduce ischemia-evoked amino acid efflux. [source] In vitro starch digestibility of fresh and sun-dried faba beans (Vicia faba L.)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2007Luis A Bello-Pérez Abstract Fresh and sun-dried faba beans (Vicia faba L.) were cooked, stored for various times at 4 °C and analysed for available starch (AS), resistant starch (RS) and fibre-associated resistant starch (FARS) contents as well as ,-amylolysis. Fresh beans required a shorter cooking time (25 min) than dried beans (158 min). Cooked fresh faba beans had a higher AS content than cooked dried faba beans. The AS content in both decreased during cold storage, with fresh beans showing a smaller decrease than dried beans with increasing storage time. Cooked fresh faba beans also had a higher total RS content than cooked dried faba beans, although a greater increase in RS content was recorded in the latter upon storage. Starch retrogradation was more prominent in cooked dried faba beans than in cooked fresh faba beans, as indicated by the consistently higher FARS content. The ,-amylolysis rate decreased with increasing storage time, i.e. long-stored (72 h) cooked faba beans exhibited slower starch digestion, and differences were recorded between fresh and dried beans. The predicted glycaemic index ranged between 60.9 and 58.0% for cooked fresh faba beans and between 57.9 and 55.8% for cooked dried faba beans, which is suggestive of slow glucose release from starch in faba beans. Copyright © 2007 Society of Chemical Industry [source] Evidence that endogenous inosine and adenosine-mediated hyperglycaemia during ischaemia,reperfusion through A3 adenosine receptorsAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 4 2009D. Cortés Summary 1,The molecular mechanism underlying stress-induced hyperglycemia has not been comprehensively clarified. Recently, we demonstrated in ischaemia-reperfusion (I-R) stress-subjected liver that inosine and adenosine are mainly responsible for the hyperglycemia observed. 2,We aimed to advance in the knowledge of the role of inosine plus adenosine as mediators of hepatic-induced hyperglycemia detected after I-R in lower limbs. 3,Acute ischaemia was conducted in anesthetized rats by occluding downstream abdominal aorta and cava vein; then, reperfusion was allowed. Blood samples from hepatic or abdominal cava veins were taken throughout the experiments to measure glucose, inosine and adenosine. Antagonists to adenosine (AdoR) and adrenergic receptors (AdrR) were administered during ischaemia to analyze their effect on hepatic glucose release. 4,Ischaemia up to 60 min produced minor increase of glucose and nucleosides blood values, but 5 min of ischaemia followed by 2- (or 10-) min reperfusion increased glucose 23%, and those of inosine or adenosine by 100%. After 60 min of ischaemia and 10 min of reperfusion, glycemia rose 2-fold and blood inosine and adenosine, 3.3- and 2.7-fold, respectively. A linear positive correlation, r2, as high as 0.839 between glucose and either nucleoside blood values was calculated. The hyperglycemia response to I-R decreased by 0, 25, 33, 45 and 100% after selective inhibition of A2B AdoR, A2A AdoR, a1B AdrR, A1 AdoR, and A3 AdoR, respectively. 5,Inosine-adenosine couple through activation of hepatic A3 AdoR is the main signal for releasing glucose from liver glycogen and for promoting hyperglycemia following experimental injury of I-R from lower limbs. [source] Effect of enzyme supplementation at moderate cellulase loadings on initial glucose and xylose release from corn stover solids pretreated by leading technologiesBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Rajeev Kumar Abstract Moderate loadings of cellulase enzyme supplemented with ,-glucosidase were applied to solids produced by ammonia fiber expansion (AFEX), ammonia recycle (ARP), controlled pH, dilute sulfuric acid, lime, and sulfur dioxide pretreatments to better understand factors that control glucose and xylose release following 24, 48, and 72 h of hydrolysis and define promising routes to reducing enzyme demands. Glucose removal was higher from all pretreatments than from Avicel cellulose at lower enzyme loadings, but sugar release was a bit lower for solids prepared by dilute sulfuric acid in the Sunds system and by controlled pH pretreatment than from Avicel at higher protein loadings. Inhibition by cellobiose was observed to depend on the type of substrate and pretreatment and hydrolysis times, with a corresponding impact of ,-glucosidase supplementation. Furthermore, for the first time, xylobiose and higher xylooligomers were shown to inhibit enzymatic hydrolysis of pure glucan, pure xylan, and pretreated corn stover, and xylose, xylobiose, and xylotriose were shown to have progressively greater effects on hydrolysis rates. Consistent with this, addition of xylanase and ,-xylosidase improved performance significantly. For a combined mass loading of cellulase and ,-glucosidase of 16.1 mg/g original glucan (about 7.5 FPU/g), glucose release from pretreated solids ranged from 50% to75% of the theoretical maximum and was greater for all pretreatments at all protein loadings compared to pure Avicel cellulose except for solids from controlled pH pretreatment and from dilute acid pretreatment by the Sunds pilot unit. The fraction of xylose released from pretreated solids was always less than for glucose, with the upper limit being about 60% of the maximum for ARP and the Sunds dilute acid pretreatments at a very high protein mass loading of 116 mg/g glucan (about 60 FPU). Biotechnol. Bioeng. 2009;102: 457,467. © 2008 Wiley Periodicals, Inc. [source] Influence of substrate particle size and wet oxidation on physical surface structures and enzymatic hydrolysis of wheat strawBIOTECHNOLOGY PROGRESS, Issue 2 2009Mads Pedersen Abstract In the worldwide quest for producing biofuels from lignocellulosic biomass, the importance of the substrate pretreatment is becoming increasingly apparent. This work examined the effects of reducing the substrate particle sizes of wheat straw by grinding prior to wet oxidation and enzymatic hydrolysis. The yields of glucose and xylose were assessed after treatments with a benchmark cellulase system consisting of Celluclast 1.5 L (Trichoderma reesei) and Novozym 188 ,-glucosidase (Aspergillus niger). Both wet oxidized and not wet oxidized wheat straw particles gave increased glucose release with reduced particle size. After wet oxidation, the glucose release from the smallest particles (53,149 ,m) reached 90% of the theoretical maximum after 24 h of enzyme treatment. The corresponding glucose release from the wet oxidized reference samples (2,4 cm) was ,65% of the theoretical maximum. The xylose release only increased (by up to 39%) with particle size decrease for the straw particles that had not been wet oxidized. Wet oxidation pretreatment increased the enzymatic xylose release by 5.4 times and the glucose release by 1.8 times across all particle sizes. Comparison of scanning electron microscopy images of the straw particles revealed edged, nonspherical, porous particles with variable surface structures as a result of the grinding. Wet oxidation pretreatment tore up the surface structures of the particles to retain vascular bundles of xylem and phloem. The enzymatic hydrolysis left behind a significant amount of solid, apparently porous structures within all particles size groups of both the not wet oxidized and wet oxidized particles. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Optimization of Reaction Conditions for Enzymatic Viscosity Reduction and Hydrolysis of Wheat Arabinoxylan in an Industrial Ethanol Fermentation ResidueBIOTECHNOLOGY PROGRESS, Issue 2 2006Hanne R. Sřrensen This study examined enzyme-catalyzed viscosity reduction and evaluated the effects of substrate dry matter concentration on enzymatic degradation of arabinoxylan in a fermentation residue, "vinasse", resulting from industrial ethanol manufacture on wheat. Enzymatic catalysis was accomplished with a 50:50 mixture of an enzyme preparation from Humicola insolens, Ultraflo L, and a cellulolytic enzyme preparation from Trichoderma reesei, Celluclast 1.5 L. This enzyme mixture was previously shown to exhibit a synergistic action on arabinoxylan degradation. The viscosity of vinasse decreased with increased enzyme dosage and treatment time at pH 5, 50 °C, 5 wt % vinasse dry matter. After 24 h of enzymatic treatment, 76,84%, 75,80%, and 43,47%, respectively, of the theoretically maximal arabinose, xylose, and glucose releases were achieved, indicating that the viscosity decrease was a result of enzyme-catalyzed hydrolysis of arabinoxylan, ,-glucan, and cellulose. In designed response surface experiments, the optimal enzyme reaction conditions with respect to pH and temperature of the vinasse, the vinasse supernatant (mainly soluble material), and the vinasse sediment (mainly insoluble substances) varied from pH 5.2,6.4 and 41,49 °C for arabinose release and from pH 4.9,5.3 and 42,46 °C for xylose release. Even though only limited hydrolysis of the arabinoxylan in the vinasse sediment fraction was obtained, the results indicated that the same enzyme activities acted on the arabinoxylan in the different vinasse fractions irrespective of the state of solubility of the substrate material. The levels of liberated arabinose and xylose increased with increased dry matter concentration during enzymatic hydrolysis in the vinasse and the vinasse supernatant, but at the same time, increased substrate dry matter concentrations gave corresponding linear decreases in the hydrolytic efficiency as evaluated from levels of monosaccharide release per weight unit dry matter. The study thus documents that enzymatic arabinoxylan hydrolysis of the vinasse significantly decreases the vinasse viscosity and that a compromise in the dry matter must be found if enzymatic efficiency must be balanced with monosaccharide yields. [source] | ||||||||||