Mixture Of Xylose Research Articles

The acetone butanol fermentation on glucose and xylose. II. Regulation and kinetics in fed‐batch cultures

The kinetics in fed-batch cultures of acetone butanol fermentation by Clostridium acetobutylicum is compared on glucose, xylose, and mixtures of both sugars. The final conversion yield of sugars into solvents always increases with the sugar feeding rate. At low feeding rates, the sugar concentration in the medium becomes limiting, which results in a slower cellular growth, a slower metabolic transition from an acid to a solvent fermentation and, thus, a higher accumulation of acids. It is only at sufficiently high feeding rates that fed-batch fermentations yield kinetic results comparable to those of batch fermentations. With mixtures of glucose and xylose, because of a maintained low glucose level, both sugars are taken up at the same rate during a first fermentation period. An earlier accumulation of xylose when the fermentation becomes inhibited suggest that xylose utilization is inhibited when the catabolic flux of glucose alone can satisfy the metabolic activity of the cell. Kinetic results with batch and fed-batch fermentations indicate several important features of the regulation of C. acetobutylicum metabolism: an early inhibition by the produced acids; an initiation of solvent formation between 4 and 6 g/L acetic and butyric acid depending on the metabolic activity of the cell; a metabolic transition from acids to solvents production at a rate closely related to the rate of sugar uptake; during solvent production, a reassimilation of acids above a minimal rate of sugar consumption of 0.2 h(-1); a final inhibition of the fermentation at a total butanol and acids concentration of ca. 20 g/L.

Regulation and butanol inhibition of D-xylose and D-glucose uptake in Clostridium acetobutylicum.

Clostridium acetobutylicum exhibited diauxie growth in the presence of mixtures of glucose and xylose. Both glucose- and xylose-grown cells had a glucose uptake activity. On the other hand, growth on xylose was associated with the induction of a xylose permease activity, which was repressed by glucose in xylose-induced cells. The rate of sugar uptake with increasing sugar concentrations showed saturation kinetics with an apparent Km of 1.25 X 10(-5) M for glucose and 5 X 10(-3) M for xylose. Concomitant with the production of solvents, the activities of the glucose and xylose transport systems decreased. Among the main products of fermentation, butanol was shown to be a potent inhibitor of the growth of the organism and of the rate of sugar uptake as well as of sugar incorporation into cell materials. These inhibitory effects of butanol were more pronounced in xylose-grown cells than in glucose-grown cells. Butanol completely inhibited growth at a concentration of 14 g/liter for cultures growing on glucose and 8 g/liter for cultures growing on xylose. Concentrations of 7 and 10.5 g/liter of butanol caused a 50% inhibition of the xylose and glucose incorporations into cell materials. These inhibitory levels of butanol were found in typical glucose or xylose fermentation.

Ethanol production during D-xylose, L-arabinose, and D-ribose fermentation by Bacteroides polypragmatus

The specific growth rate (μ) during cultivation of Bacteroides polypragmatus in 2.51 batch cultures in 4–5% (w/v) l-arabinose medium was 0.23 h-1 while that in either d-xylose or d-ribose medium was lower (μ=0.19 h-1). Whereas growth on arabinose or xylose occurred after about 6–8 h lag period, growth on ribose commenced after a 30 h lag phase. The maximum substrate utilization rate for arabinose, ribose and xylose in media with an initial substrate concentration of 4–5% (w/v) was 0.77, 0.76, and 0.60 g/l/h respectively. In medium containing a mixture of glucose, arabinose, and xylose, the utilization of all three substrates occurred concurrently. The maximum amount of ethanol produced after 72 h growth in 4–5% (w/v) of arabinose, xylose, and ribose was 9.4, 6.5, and 5.3 g/l, respectively. The matabolic end products (mol/mol substrate) of growth in 4.4% (w/v) xylose medium were 0.73 ethanol, 0.49 acetate, 1.39 CO2, 1.05 H2, and 0.09 butyrate.

Acetone-butanol production from pentoses by Clostridium acetobutylicum

Clostridium acetobutylicum fermented glucose, arabinose, and xylose with a conversion of carbon source into solvents of 32, 29, and 28% respectively. The growth yields (g cells per g sugar) were similar on the three sugars, but glucose or arabinose were consumed in preference to xylose and with faster growth (0.15 or 0.17 h-1 as compared with 0.1 h-1). Solvent yields of about 80% of the maximum were obtained using a 1:1 glucose:xylose mixture as substrate.

Purification and characterization of a xylobiose- and xylose-producing endo-xylanase from Aspergillus niger

A xylanase from a commercial Aspergillus niger pentoglycanase was purified to homogeneity by column chromatography on Ultrogel AcA 54, SP-Sephadex, Sephadex G-50, and SP-Sephadex. The enzyme hydrolyzed xylotriose slowly to xylose and xylobiose, and xylotetraose and higher xylo-oligosaccharides rapidly to mixtures of smaller xylo-oligosaccharides, with xylobiose and xylose being the preponderant final products. The anomeric configuration of the products was inverted, in contrast to the behavior of most other carbohydrases that initially produce mixtures of oligosaccharides. This enzyme is a glycoprotein having an amino acid composition high in acidic residues. Its molecular weight is 20,800 and its isoelectric point is at pH 6.7. Optimal pH values for activity and stability are between 4 and 6 and, in a 20-min assay, maximal activity is attained at 55°.

Studies on the mechanism of enzymatic hydrolysis of cellulosic substances.

Most cellulosic substances contain appreciable amounts of cellulose and hemicellulose, which on enzymatic hydrolysis mainly yield a mixture of glucose, cellobiose, and xylose. In this paper, studies on the mechanisms of hydrolysis of bagasse (a complex native cellulosic waste left after extraction of juice from cane sugar) by the cellulase enzyme components are described in light of their adsorption characteristics. Simultaneous adsorption of exo- and endoglucanases on hydrolyzable cellulosics is the causative factor of the hydrolysis that follows immediately after. It supports the postulate of synergistic enzyme action proposed by Eriksson. Xylanase pretreatment enhanced the hydrolysis of bagasse owing to the creation of more accessible cellulosic regions that are readily acted upon by exo- and endoglucanases. The synergistic action of the purified exoglucanase, endoglucanase, and xylanse has been found to be most effective for hydrolysis of bagasse but not for pure cellulose. Significant quantities of glucose are produced in beta-glucosidase-free cellulase action on bagasse. Individual and combined action of the purified cellulase components on hydrolysis of native and delignified bagasse are discussed in respect to the release of sugars in the hydrolysate.

ワラビ(<i>Pteridium aquilinum</i> var. <i>latiusculum</i> Und.) およびヤマドリゼンマイ (<i>Osmundastrum cinnamomeum</i> var. <i>fokiense Tagawa</i>) の遊離糖類について

As taste substances in Warabi (Pteridium aquilinum var. latiusculum Und.) and Yamadori-zenmai (Osmundastrum cinnamomeum var. fokiense Tagawa), free sugars were examined. The sugars were extracted by conventional means, tentatively identified by thin-layer chromatography, and were converted to O-trifluoroacetyl-sugars, which were then quantitatively analyzed by gas chromatography on Silicone DC QF-1. The linear temperature-programmed procedure was used to separate an authentic mixture of rhamnose, arabinose, xylose, fructose, galactose, mannose, glucose, sucrose, maltose, lactose and inositol into each component. Linearity of area ratio (sugar/inositol) versus molar ratio (sugar/inositol) was confirmed with arabinose, fructose, glucose and sucrose, respectively. Glucose and fructose were detected, and glucose was the major component (70_??_80%) of free sugars of Warabi and Yamadori-zenmai.

A rapid quantitative thin-layer chromatographic separation of fucose from other neutral monosaccharides an application to separate other sugars of physiological interest

Fucose can be completely separated in 65 min from seven other neutral monosaccharides of biological interest on thin layers of Kieselguhr G buffered with 0.15 M sodium dihydrogen orthophosphate. It can be determined within the range 5 to 80 μg. Using a plate 35 cm long, each of the eight individual sugar can be well separated, one from another, in 9 h. This procedure is limited to mixtures containing an upper level of 15 μg of xylose and ribose. Mixtures of fucose and xylose can be determined quantitatively by the method described.

High doses of neomycin sulfate and the absorption of glucose and xylose from the rat small intestine.

Neomycin sulfate, at doses of 250 mg./kg. or 2 gm./kg., was instilled intragastrically, in male Fisher-strain rats daily for 21 days. Pair-fed controls received an equal amount of saline intragastrically for an equal period. After 3 weeks of treatment animals were tested by our modification of the Cori method to assess the absorption of xylose, glucose, and a mixture of xylose and glucose. Rats receiving neomycin at both doses demonstrated an enhanced absorption of glucose. A significant reduction in the absorption of xylose was noted in animals treated with 2 gm./kg. of neomycin. When glucose and xylose were administered together to rats receiving 2 gm./kg. of neomycin, a significant reduction in the absorption of xylose and an enhancement in the absorption of glucose was observed.

Gas Chromatographic Sugar Analysis in Hydrolyzates of Wood Constituents. Quantitative Determination of Mixtures of Arabinose, Xylose, Mannose, Galactose and Glucose as Their Trimethylsilyl Ether Derivatives.

Gas Chromatographic Sugar Analysis in Hydrolyzates of Wood Constituents. Quantitative Determination of Mixtures of Arabinose, Xylose, Mannose, Galactose and Glucose as Their Trimethylsilyl Ether Derivatives.

Pentose metabolism in Candida: III. The triphosphopyridine nucleotide-specific polyol dehydrogenase of Candida utilis

Extracts of Candida utilis grown in the presence of xylose contain a triphosphopyridine nucleotide (TPN)-specific polyol dehydrogenase which catalyzes the reversible reduction of a number of aldoses to the corresponding polyols. The activity is low in glucose-grown cells, but growth on a mixture of glucose and xylose does not yield a diauxic growth curve, and induction of the enzyme by xylose does not appear to be prevented by the presence of glucose. The enzyme has been purified about 30-fold from extracts of commercially grown cells. The purified enzyme was active with a wide variety of sugars but appeared to prefer sugars having the hydroxyl group at carbon-2 in the d-glyccro- configuration. The reverse reaction was demonstrable with concentrations of polyol in the range of 0.1–0.3 m. The Michaelis constants for d-xylose and xylitol were found to be 2.8 × 10 −2 and 0.53 m, respectively, and for TPNH and TPN, 1.6 × 10 −5 and 1.4 × 10 −4 m, respectively. There is no activity with DPNH or DPN. The purified enzyme preparations are homogeneous in disc gel electrophoresis and by sedimentation analysis. The molecular weight obtained by equilibrium ultracentrifugation was 69,700. Amino acid analysis showed the enzyme to be rich in acidic and neutral amino acids and poor in methionine, half-cystine, and histidine.

Enzymic synthesis of 3-O-alpha-D-glucopyranosyl D-xylose.

TRANSGLYCOSYLATION reactions with microbial enzymes offer a facile method for the synthesis of new oligosaccharides. Following our earlier report1 on the production of 3-O-β-D-glucopyranosyl D-xylose by the action of a cell-free extract of A. niger 152 on a cellobiose–xylose mixture, the corresponding disaccharide containing an α-glucosidic linkage has now been synthesized via the following reaction : catalysed by a transglycosylase from Penicillium lilacinum.

The proximate analysis of wheat flour carbohydrates. III.—the estimation of the hemicellulose fraction

AbstractThe composition of the hemicellulose fractions of wholemeal and flours of about 70% extraction in terms of anhydro‐arabinose, xylose and uronic acid units has been investigated. It has been shown that the hemicelluloses, on distillation with hydrochloric acid, behave in the same manner as an equimolecular mixture of arabinose and xylose. Xylose is a suitable standard for the distillation process, and the ‘xylose equivalent’ of a wheat fraction multiplied by 0.97 is a quantitative measure of the hemicellulose present, provided this is not less than 1.8%.

Determination of Small Quantity of Pentosan in Cellulosic Materials

Abstract 1. For the estimation of a small quantity of pentosan in cellulosic materials, an improvement of phloroglucin method and colorimetry with aniline were investigated on mixtures of glucose and xylose, and the results were compared with brornate, the usual phloroglucin and barbituric acid methods. 2. Treatment of the undried phloroglucide with alcohol remarkably removes the influence of hexosan on pentosan determination but it is not complete. As the solubility of the furfural-phloroglucide increases with phloroglucin added, it is desirable to increase the amount of the latter to twice the theoretical. 3. Colorimetry with aniline is superior to other methods. The color reaction is stable at low temperatures. 4. Pentosan contents of some cellulosic materials, such as rayons, pulps and cellulose acetates, are tabulated.