Search

Flavonoids isolated from citrus were evaluated for their ability to affect the inflammation response through suppression of cytokine expression by human monocytes. Several polymethoxylated flavones inhibited lipopolysaccharide-induced monocyte expression of tumor necrosis factor (TNFα). Subsequent studies centered on the compound 3,5,6,7,8,3‘,4‘-heptamethoxyflavone (HMF) which produced the highest inhibition (IC50 = 5 μM). HMF was also a potent inhibitor of macrophage inflammatory protein-1α (MIP-1α) and interleukin-10 (IL-10) production, but not of IL-1β, IL-6, or IL-8 production. Suppression of TNFα production was at the level of mRNA induction as determined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). HMF was also a potent inhibitor of human phosphodiesterase activity and was shown to induce a substantial elevation of cAMP levels in monocytes. The similarity of these results to the inhibition profile of the known phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine, suggests that the polymethoxylated flavones inhibit cytokine production in part by suppression of phosphodiesterase activity. The ability of HMF to also inhibit IL-10 production suggests the additional existence of a phosphodiesterase-independent mechanism for this compound.

Abstract: Acidothermus cellulolyticus, an isolate from hot springs at Yellowstone National Park, produced cellulase enzyme when grown in cellobiose-containing medium. The cellulase production, cell growth, and cellobiose degradation rates of batch culture in 2.5, 5.0, 7.5, and 10.0 g/L of cellobiose as a substrate were studied. The specific growth rates were measured, and the μmax and Ks values based on these data were 0.2 h−1 and 0.3 g cellobiose/L using the Monod equation. The maximum cellulase activities (21–69 U/L) and volumetric productivities (between 0.92 and 2.49 U/L-h) were proportional to the concentration of cellobiose. Greatest cellulase production in batch culture was achieved by use of secondary cellulosic substrates. Mixed substrate systems consisting of 5 g/L cellobiose and various Avicel concentrations (5, 10, and 16 g/L) were also studied in batch culture. The maximum cellulase activities were53, 62, and 78 U/L, respectively. The enzyme production rate could be related to Avicel using the Monod equation. Here, maximum volumetric productivity, υmax, was found to be 2.15 U/L-h and Ks was 7.5 g Avicel/L. Another mixed substrate system, consisting of 5 g/L cellobiose and 15 g/L Solka Floc, produced a maximum cellulase concentration of 105 U/L.

Abstract: Large-scale production of ethanol or other transportation fuels by biological conversion of lignocellulosic biomass will eventually require integration with large-scale production of biomass substrates. The most promising candidates for efficient production of biomass in the US are short rotation hardwoods and herbaceous crops. The following samples of short rotation hardwoods were provided by the Biomass Production Program managed for the Department of Energy Biofuels and Municipal Waste Technology Division by the Oak Ridge National Laboratory: Poplar hybrid NE388(Populus, maximowiczii xP. trichocarpa), Poplar hybrid Nil (Populus. trichocarpa xP. deltoides), and Sweetgum(Liquidambar styraciflua). Samples of two short rotation grasses (weeping lovegrass and switchgrass) and one herbaceous legume (sericea lespedeza) were also obtained from the same source. Milled and debarked hardwoods and herbaceous samples were subjected to prehydrolysis with dilute sulfuric acid at 140 and 160 °C for reaction times ranging from 5 to 60 min. The dilute sulfuric acid hydrolyzed all hemicelluloses at longer reaction times (30–60 min at 140 °C and 5–10 min at 160 °C), but solubilized very small amounts (< 15%) of lignin and cellulose. Cellulose in all three pretreated hardwoods became highly digestible by cellulase enzyme fromTrichoderma reesei. The two grasses also responded to dilute acid pretreatment very well.

Enzymatic hydrolysates of orange peel contain relatively high levels of galacturonic acid and arabinose which are not fermentable to ethanol by yeasts. We observed complete utilization of both sugars during fermentation of peel hydrolysates by the ethanologenic construct of E. coliKO11. The bacterium exhibits a novel pattern of galacturonic acid fermentation producing equimolar amounts of acetate and ethanol accompanied by carbon dioxide.

Hydrolysis of polysaccharides in comminuted orange peel by commercial cellulase and pectinase enzymes has been investigated. High levels of conversion to monomeric sugars were observed after treatment with pectinase enzyme, but cellulase enzyme achieved only limited solubilization. The combination of cellulase and pectinase enzymes appears to be a most efficient system for enzymatic hydrolysis of polysaccharides in orange peel.

The thermal stability of a purifiedAspergillus nigerβ-glucosidase (EC 3.2.1.21) has been dramatically increased by intramolecular crosslinking with glutaraldehyde at pH 9.0, followed by borohydride reduction. The stabilization has been shown to be due to the formation of a distinct subpopulation of enzyme molecules, the activity of which has a half-life at 65°C of approximately 40 hours, which is some 80 times as long as that of the native enzyme at this temperature.

Xylose isomerase was purified from a transformedE. colistrain (LE392-pRK248/pTXI-1) (Lastick et al., 1986) that overproduces the enzyme by induction of the strong lambda PLpromotor. Kinetic data, N-terminal sequence analysis, SDS polyacrylamide gel electrophoresis, size exclusion chromatography and immunodiffusion were used to compare the overproduced enzyme with xylose isomerase purified from xylose induced, non-transformedE. coliLE392 cells; no differences between these purified enzyme preparations were found.

Cellulolytic enzymes from a laboratory anaerobic digester fed municipal solid waste were examined with respect to pH and temperature. The pH optimum was pH 6.6, considerably lower than the pH range in which digesters are normally operated (pH 7.2–7.6). The optimum temperature was between 50 and 60°C, rather than the 35–37°C range in which most digesters are controlled.

Commercially available maltodextrins were subjected to high pressure size exclusion chromatography (HPSEC) on Toyo Soda G 2000 PW columns with water as the mobile phase. The elution profiles of these samples will allow researchers to select the correct maltodextrin for growth studies requiring specific dextrin oligomers. Characterization of the chromatography system with standards of known molecular weight allows estimation of the weight average molecular weight of polydisperse dextrins. The enzymatic hydrolysis of dextrin by bacterialα-amylase and fungal glucoamylase was also monitored by HPSEC.

Abstract: The successful production of novel biodegradable plastic copolymers incorporating both synthetic plastic formulations, such as polystyrene, and naturally occurring biodegradable polymer components, such as cellulose, starch, or xylan, requires stable chemical bonding between these polymers. Modification of the natural polymers through acetylation of the available hydroxyl groups permits the formation of appropriate film-forming plastic copolymers. However, modification of natural polymers has been demonstrated to result in decreased attack by microbial catalysts. For this study, the abundant natural polymers cellulose, starch, and xylan were substituted with acetate to various degrees, and the effect of this modification on the anaerobic biodegradation was assessed using the biochemical methane potential (BMP) protocol. Significant reduction in anaerobic biodegradability resulted with all polymers at substitution levels of between 1.2-1.7. For the xylan acetate series, the trends for anaerobic biodegradation were in good agreement with reduced enzymatic hydyolysis using commercially available xylanase preparations.

Abstract: The thermal denaturation of four purified Trichoderma reesei cellulase components, cellobiohydrolase (CBH) I, CBH II, endoglucanase (EG) I, and EG II, has been monitored using a combination of classical temperature/activity profiles, differential scanning calorimetry (DSC), and thermal scanning fluorescence emission spectrometry. Significant correlations were found between the results of enzyme activity studies and the results obtained through the more direct physical approaches, in that both DSC and the activity studies showed EG II (Tm = 75°C) to be much more thermostable (by 10–11 °C) than the other three enzymes, all three of which were shown by both activity profiles and DSC to be very similar in thermal stability. The temperature dependence of the wavelength of maximum tryptophan emission showed a parallel result, with the three enzymes exhibiting less thermostable activity being grouped together in this regard, and EG II differing from the other three in maintaining a less-exposed tryptophan microenvironment at temperatures as high as 73 °C. The DSC results suggested that at least two transitions are involved in the unfolding of each of the cellulase components, the first (lower-temperature) of which may be the one correlated with activity loss.

Abstract: As a prerequisite for the enzymatic saccharification or simultaneous saccharification and fermentation process for ethanol synthesis, a dilute-acid pretreatment of the biomass has been shown to be a very effective first step in the yeast-catalyzed bioprocess. Three hardwoods (silver maple, sycamore, and black locust) and two corn residues (cobs and stover) were chosen and subjected to prehydrolysis with dilute sulfuric acid at 140 and 160 °C for reaction times ranging from 5 to 60 min. Although the hemicelluloses from all five samples could be completely hydrolyzed at both 140 and 160 °C, hydrolysis at 160 °C for the woods and stover produced a superior substrate for the cellulase enzyme from Trichoderma reesei, in which > 90% of the cellulose was hydrolyzed by the enzyme. Corn cobs produced an excellent substrate after only 5 min at 140°C. Small amounts of lignin and glucan were also solubilized by the acid in all samples.

Zur Identifizierung organischer stickstoffhaltiger niedermolekularer Stoffe in Kläranlagenabläufen wurden verschiedene Ablaufproben einer Belebtschlamm-Kläranlage mit Nitrifikationsstufe, in der kommunales Abwasser behandelt wird (10000 EWG), herangezogen. Nach Entwicklung von Anreicherungsmethoden an Reversed-Phasen wurden die angereicherten Stoffgemische ohne Derivatisierung unter verschiedenen Bedingungen gaschromatographisch (GC) aufgetrennt und massenspektrometrisch (MS) ausgewertet. Die unter Anwendung des PBM-Algorithmus ausgewerteten GC/MS-Spektren der angereicherten Proben (Anreicherungsfaktor 1000...20000) ergaben 133 Stickstoffverbindungen, die mit einer Wahrscheinlichkeit von mindestens 30% ausgegeben wurden. Davon wurden siebzehn Verbindungen mit einer Übereinstimmungszahl > 90% und zehn mit einer Übereinstimmungszahl zwischen 80 und 90% identifiziert. Darunter auch 9-Methylacridin, das in neun von zehn verschiedenen Proben gefunden wurde. Der erfaßte niedermolekulare Anteil am DON (gelöster organisch gebundener Stickstoff) wurde zu 20% abgeschätzt, wobei der höhermolekulare Anteil am DON maximal 70% beträgt.

The elution behavior of 28 sugars and related compounds from high performance chromatography columns packed with alkaline earth and transition metals was investigated. As expected from the well-known chromatography of the commercially available calcium, silver, and lead form columns, elution behavior is highly metal-ion form specific. A significant data base of sugar elution versus column cationic-form was generated to permit the selection of new columns to enhance the separation of specific eluting species. Sugars resulting from the hydrolysis of wood were closely examined. Arabinose and galactose, known to be difficult to separate on commercially available lead and silver-form columns, were well separated on custom-packed rubidium and cesium-form columns.

1,4-beta-D-Glucan glucohydrolase (exo-1,4-beta-D-glucosidase) (EC 3.2.1.74) was isolated from growth supernatants of Torulopsis wickerhamii and was subjected to hydrodynamic, optical (CD), and kinetic analysis after purification to homogeneity by ammonium sulfate precipitation, size exclusion chromatography, ion exchange chromatography, and isopycnic banding centrifugation in cesium chloride. The last step was found to separate the enzyme from strongly associating, high molecular weight polysaccharide. Enzyme homogeneity was established by isoelectric focusing, sodium dodecyl sulfate-gel electrophoresis, and analytical high performance size exclusion chromatography using dual detection. The native exo-1,4-beta-D-glucosidase was found to be a dimer of 151,000 +/- 21,100 daltons by high performance size exclusion chromatography and 143,600 +/- 1,800 daltons by sedimentation equilibrium. The enzyme has a 12% linked carbohydrate content (mostly mannose) and no essential metal ions. Hydrolysis of p-nitrophenyl-beta-D-glucopyranoside was found to be optimal at pH 4.25 and 50 degrees C. The enzyme was found to produce beta-D-glucose from cellodextrins (indicating retention of anomeric configuration during hydrolysis) and demonstrated depolymerization from the non-reducing polymer terminus. The enzyme followed competitive type inhibition with p-nitrophenyl-beta-D-glucopyranoside as substrate and demonstrated high values of Ki for D-glucose and D-cellobiose inhibition (190 and 230 mM, respectively). The exo-1,4-beta-D-glucosidase was found to hydrolyze cellotetraose more rapidly than D-cellobiose and aryl-beta-D-glycosides more rapidly than all other substrates. Low levels of activity were found for the polymeric substrates beta-glucan (yeast cell walls), Avicel, and Walseth cellulose. Although this enzyme demonstrates broad disaccharide substrate specificity, a characteristic common to beta-D-glucosidases from many sources, the ability to hydrolyze higher cellodextrins more rapidly than cellobiose renders this enzyme the first exo-1,4-beta-D-glucosidase purified from yeast.

Ethanol was produced from xylose by converting the sugar to xylulose, using commercial xylose isomerases, and simultaneously converting the xylulose to ethanol by anaerobic fermentation using different yeast strains. The process was optimized with the yeast strain Schizosaccharomyces pombe (Y-164). The data show that the simultaneous fermentation and isomerization of 6% xylose can produce final ethanol concentrations of 2.1% w/v within 2 days at temperatures as high as 39°C.

Abstract: The conversion of monosaccharides in organe peel hydrolysates to ethanol by recombinantEscherichia coli KO11 has been investigated in pH-controlled batch fermentations at 32 and 37°C. pH values and concentration of peel hydrolysate were varied to determine approximate optimal conditions and limitations of these fermentations. Very high yields of ethanol were achieved by this microorganism at reasonable ethanol concentrations (28–48 g/L). The pH range between 5.8 and 6.2 appears to be optimal. The microorganism can convert all major monosaccharides in organe peel hydrolysates to ethanol and to smaller amounts of acetic and lactic acids. Acetic acid is coproduced in equimolar amounts with ethanol by catabolism of salts of galacturonic acid.

Abstract: Lignocellulosic biomass is one of the most plentiful and potentially cheapest feedstocks for ethanol production. The cellulose component can be broken down into glucose by enzymes and then converted to ethanol by yeast. However, hydrolysis of cellulose to glucose is difficult, and some form of pretreatment is necessary to increase the susceptibility of cellulose to enzymatic attack. An analysis has been completed of two pretreatment options, dilute sulfuric acid hydrolysis and sulfur dioxide impregnated steam explosion, for two feedstocks, wheat straw and aspen wood chips. Detailed process flow sheets and material and energy balances were used to generate equipment cost information. A technical and economic analysis compared the two feedstocks for each of the two pretreatments. For the same pretreatment, sugars produced from aspen wood hydrolysis were cheaper because of the higher carbohydrate content of aspen, whereas dilute acid pretreatment is favored over acid-catalyzed steam explosion.

Abstract: Considerable controversy exists concerning the role lignin plays in the adsorption of cellulase enzymes on biomass. Recent studies using extracted, purified hardwood lignin have shown these materials have a propensity for cellulase adsorption; however, native lignin is carbohydrate-linked and far less condensed. In this study, we report the results of adsorption-kinetics analyses of cellulase-complex activities using five pretreated aspen substrates, including an exhaustively enzyme-hydrolyzed one. These data indicate that the polymer-binding cellulase activities are removed from solution at higher rates and extents in the presence of low lignin-content versus high lignin-content substrates. This order of adsorption was found to be essentially the inverse for beta-glucosidase adsorption.

Abstract: A preliminary process design for dilute sulfuric acid pretreatment of aspen wood chips in order to obtain fermentable sugars has been prepared and subjected to an economic evaluation. The process design was prepared according to experimental data on the kinetics of dilute sulfuric acid prehydrolysis and particle size effects obtained in this study and our previous work. The initial economic evaluation shows woodchips are 56% of the cost of production, whereas the reactor is only 4%, and the comminution operation is just under 10%, indicating that the process economics are extremely vulnerable to feedstock costs and are thus yield-sensitive. Although chances for major cost improvements by modification of the reactor design and finding alternatives to dry milling of aspen chips to small (20–80 mesh) particles needed for acid penetration and enzymatic saccharification are not great, design improvements of the process will necessitate development of a cheaper acid resistant pretreatment reactor and a less energy intensive comminution system. Experimental results on effects of particle size on the dilute acid pretreatment design are presented.

To assess optimal saccharification performance, α-cellulose and dilute acid pretreated aspen (DAA) wood meal were subjected to various loadings of commercial cellulase and β-D-glucosidase preparations. Fifteen international filter paper units (IFPU)/g cellulose content and 30 IFPU/g cellulose content were required to digest 95% of the available cellulose in α-cellulose and pretreated aspen, respectively. The optimal supplementation ratios, based on Genencor GC 123 cellulase and β-D-glucosidase from Novo SP 188 for the α-cellulose and DAA digestions range from 0.25 to 0.5 and 0.12 to 0.25, respectively.

A promoterles DNA fragment containing theE. colixylose isomerase gene and its ribosome binding site was ligated into a plasmid downstream from the strong λ PLpromoter. The plasmid was then used to transformE. colistrains containing a temperature-sensitive λ repressor (cI857). The transformants overproduced xylose isomerase when the repressor was thermally inactivated.

Zusammenfassung In einem Elektronen-Interferometer werden die Interferenzfiguren hinter Biprismafäden beobachtet, die mit einem Ferromagnetikum bedampft wurden. Bei Verwendung von Eisen ist der sonst geradlinige Verlauf der Interferenzstreifen stark gestört, bei Permalloy dagegen nicht. Der magnetische Fluß ist also bei Permalloyschichten längs des Fadens konstant, es treten keine Streufelder auf. — Bis zur halben Länge mit Permalloy bedampfte Biprismafäden ermöglichen die quantitative Überprüfung der vonEhrenberg undSiday undAharonov undBohm angegebenen Beziehung für die phasenschiebende Wirkung des magnetischen Vektorpotentials auf Elektronenwellen. Der experimentell gefundene Wert der Flußeinheit vonF2p = 3,93·10-7 Gß cm2 bestätigt den von der Theorie dafür geforderten Werth/e= 4,13·10-7 Gß cm2 innerhalb der Meßgenauigkeit.

Zusammenfassung Dünne Permalloy-Schichten werden mit schnellen Elektronen durchstrahlt. Infolge der magnetischen Ablenkung stellen entgegengesetzt magnetisierte Bereiche dieser Schichten für die Elektronen ein Biprisma dar. Die hinter diesem beobachtbaren Interferenzen lassen sich vollständig nur mit Hilfe der phasenschiebenden Wirkung des Vektorpotentials beschreiben. Eine Berechnung mit virtuellen Quellen läßt nämlich die Lage der Interferenzstreifen unbestimmt, da die Phasenbeziehungen zwischen den virtuellen Quellen nicht angegeben werden können. Im zweiten Teil werden die Beugung und die Ausdehnung der Bereichsgrenzen berücksichtigt, indem das Fresnelsche Beugungsbild des magnetischen Biprismas berechnet wird. Der Vergleich mit den Beobachtungen läßt auf eine Bereichswanddicke von etwa 2500 Å schließen.

Zusammenfassung Zum Nachweis der phasenschiebenden Wirkung des magnetischen Vektorpotentials auf Elektronenwellen wurde ein Zweistrahl-Interferometer benutzt, in dem die beiden Wellenfelder ein mit dem magnetischen Fluß erfülltes Gebiet umgeben, ohne es zu durchdringen. Die Interferenzfigur kann als Beugungserscheinung unter Berücksichtigung der magnetischen Phasenschiebung mit Hilfe des Kirchhoffschen Beugungsintegrals behandelt werden. Als Folge der magnetischen Phasenschiebung ergeben sich in Übereinstimmung mit dem Experiment Unsymmetrien in der Intensitätsverteilung, die sich beim Umpolen des magnetischen Flusses spiegelbildlich umkehren.

Zusammenfassung Schnelle Elektronen, die dünne ferromagnetische Schichten durchstrahlen, werden durch die Lorentz-Kraft aus der Primärrichtung abgelenkt. An der Grenze zweier antiparallel magnetisierter Weißscher Bezirke können derartige Umlenkungen zu Zweistrahlinterferenzen Anlaß geben, die auch mit einer geeigneten Anordnung experimentell nachgewiesen wurden. Die Intensität der Erscheinung in der Endbildebene des elektronenoptischen Strahlenganges ist bei gegebener Strahlspannung nur von der magnetischen Ablenkung, der Breite des Übergangsbereiches im Biprisma (Bloch-Wand) und der Streifenzahl abhängig. Das Auftreten der Zweistrahlinterferenzen beweist, daß das Vektorpotential im Sinne vonAharonov undBohm eine direkte physikalische Wirkung auf die Elektronen ausübt.

Zusammenfassung Magnetfelder stellen für Elektronenwellen Phasenobjekte dar, an denen Beugung auftreten kann. Mit der Kirchhoffschen Formel wird das Beugungsbild berechnet, das hinter einem Objekt mit schwach ablenkendem Magnetfeld entsteht.

TFA-amino acid esters and TFA-dipeptide esters have been employed as optically active stationary phases for the resolution of amino acid enantiomers by gas chromatography. Structural consideration of the hydrogen bonded diastereoisomeric association complex formed during the separation of amino acid enantiomers led to the synthesis of an N-acyl-amino acid n-alkyl amide (N-caproyl-L-valine n-hexyl amide). This amino acid derivative fulfills the general requirements for the reversible association between the enantiomers and the asymmetric solvent molecules. The results obtained show that the amide portion, when in competition with the ester portion of a dipeptide phase, is involved in formation of the diastereoisometric association complex between the enantiomeric solutes and the chiral solvent by hydrogen bonds.

32P-labeled (in vivo) øX174 RFI DNA was restricted by Hinc II. Three aliquots of the same digest: a) nondenatured, b) heat denatured, and c) denatured by 5 mM Me-HgOH were analyzed on 3-15% acrylamide gelgradients or on 3% gels with reduced N,N′-methylene-bis-acrylamide. The autoradiography of the gels showed that the nondenatured sample migrates two times faster than the denatured samples. After denaturation each original fragment appeared as a doublet. Using in vitro synthesized RFI DNA labeled only in negative strand with 32P we could identify the position of the negative strand in each denatured doublet. The single strand DNA fragments could be recovered from the gel slices on a semi-preparative scale by electrophoresis into dialysis tubing.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.