The influence of other hemicellulosic sugars (arabinose, galactose, mannose, and glucose), oxygen limitation, and initial
xylose concentration on the fermentation of xylose to xylitol was in vestigated using experimental design methodology. Oxygen
limitation and initial xylose concentration had strong influences on xylitol production by Candida tropicalis ATCC 96745. Under semiaerobic conditions, xylitol yield was highest (0.62 g/g), whereas under aerobic conditions volumetric
productivity was highest (0.90g/[L·h]). In the presence of glucose, xylose utilization was strongly repressed and sequential
sugar utilization was observed. Ethanol produced from the glucose caused a 50% reduction in xylitol yield when the ethanol
con centration exceeded 30 g/L. When complex synthetic hemicellulosic sugars were fermented, glucose was initially consumed
followed by a simultaneous uptake of the other sugars. The highest xylitol yield (0.84 g/g) and volumetric productivity (0.49
g/[L·h]) were obtained for substrates containing high arabinose and low glucose and mannose contents. 相似文献
An innovative green column-switching high-performance liquid chromatographic (HPLC) technique was developed by coupling traditional and Pb2+ ion-exclusion columns to study enzyme hydrolysis components of waste cellulosic biomass. Pure water was used as the mobile phase to separate neutral polar analytes in high salt content solution. The column-switching HPLC-RI was connected on-line to the immobilized enzyme reactor for successive on-line desalting and simultaneous analysis of six carbohydrates (cellobiose, glucose, xylose, galactose, mannose, and arabinose) in the hydrolysate of waste paper and waste tree branch by incorporating the heart-cut and the elution-time-difference techniques. Six internal standard calibration curves in the linear concentration range of 0–2000 μg mL−1 were prepared. Xylitol was used as the internal standard to give excellent linear correlation coefficients (0.9984–0.9999). The limits of detection and quantification for cellobiose, glucose, xylose, galactose, mannose, and arabinose varied between 0.12–4.88 and 0.40–16.3 μg mL−1, respectively, with an accuracy of 90–102% and a precision of 0.1–7.8%. Cellulose and hemicellulose contents were higher in waste paper than in waste tree branch. 相似文献
The potential of dilute-acid prehydrolysis as a pretreatment method for sugarcane bagasse, rice hulls, peanut shells, and cassava stalks was investigated. The prehydrolysis was performed at 122 degrees C during 20, 40, or 60 min using 2% H(2)SO(4) at a solid-to-liquid ratio of 1:10. Sugar formation increased with increasing reaction time. Xylose, glucose, arabinose, and galactose were detected in all of the prehydrolysates, whereas mannose was found only in the prehydrolysates of peanut shells and cassava stalks. The hemicelluloses of bagasse were hydrolyzed to a high-extent yielding concentrations of xylose and arabinose of 19.1 and 2.2 g/L, respectively, and a xylan conversion of more than 80%. High-glucose concentrations (26-33.5 g/L) were found in the prehydrolysates of rice hulls, probably because of hydrolysis of starch of grain remains in the hulls. Peanut shells and cassava stalks rendered low amounts of sugars on prehydrolysis, indicating that the conditions were not severe enough to hydrolyze the hemicelluloses in these materials quantitatively. All prehydrolysates were readily fermentable by Saccharomyces cerevisiae. The dilute-acid prehydrolysis resulted in a 2.7- to 3.7-fold increase of the enzymatic convertibility of bagasse, but was not efficient for improving the enzymatic hydrolysis of peanut shells, cassava stalks, or rice hulls. 相似文献
A process was developed to fractionate corn fiber into glucose- and pentose-rich fractions. Corn fiber was ammonia fiber explosion treated at 90 degrees C, using 1 g anhydrous ammonia pergram of drybiomass, 60% moisture, and 30-min residence time. Twenty four hour hydrolysis of ammonia fiber explosion-treated corn fiber with cellulase converted 83% of available glucanto-glucose. In this hydrolysis the hemicellulose was partially broken down with 81% of the xylan and 68% of the arabinan being contained in the hydrolysate after filtration to remove lignin and other insoluble material. Addition of ethanol was used to precipitate and recover the solubilized hemicellulose from the hydrolysate, followed by hydrolysis with 2% (v/v) sulfuric acid to convert the recovered xylan and arabinan to monomeric sugars. Using this method, 57% of xylose and 54% of arabinose available in corn fiber were recovered in a pentose-rich stream. The carbohydrate composition of the pentose-enriched stream was 5% glucose, 57% xylose, 27% arabinose, and 11% galactose. The carbohydrate composition of the glucose-enriched stream was 87% glucose, 5% xylose, 6% arabinose, and 1% galactose, and contained 83% of glucose available from the corn fiber. 相似文献
Biological conversion of biomass into fuels and chemicals requires hydrolysis of the polysaccharide fraction into monomeric sugars prior to fermentation. Hydrolysis can be performed enzymatically or with mineral acids. In this study, dilute sulfuric acid was used as a catalyst for the pretreatment of rapeseed straw. The purpose of this study is to optimize the pretreatment process in a 15-mL bomb tube reactor and investigate the effects of the acid concentration, temperature, and reaction time. These parameters influence hemicellulose removal and production of sugars (xylose, glucose, and arabinose) in the hydrolyzate as well as the formation of by-products (furfural, 5-hydroxymethylfurfural, and acetic acid). Statistical analysis was based on a model composition corresponding to a 33 orthogonal factorial design and employed the response surface methodology to optimize the pretreatment conditions, aiming to attain maximum xylan, mannan, and galactan (XMG) extraction from hemicellulose of rapeseed straw. The obtained optimum conditions were: H2SO4 concentration of 1.76% and temperature of 152.6 °C with a reaction time of 21 min. Under these optimal conditions, 85.5% of the total sugar was recovered after acid hydrolysis (78.9% XMG and 6.6% glucan). The hydrolyzate contained 1.60 g/L glucose, 0.61 g/L arabinose, 10.49 g/L xylose, mannose, and galactose, 0.39 g/L cellobiose, 0.94 g/L fructose, 0.02 g/L 1,6-anhydro-glucose, 1.17 g/L formic acid, 2.94 g/L acetic acid, 0.04 g/L levulinic acid, 0.04 g/L 5-hydroxymethylfurfural, and 0.98 g/L furfural. 相似文献
Flocculation is a desirable property in industrial yeasts and is particularly important in the fuel ethanol industry because it provides a simple and cost-free way to separate yeast cells from fermentation products. In the present study, the effect of pH and lignocellulose-derived sugars on yeast flocculation was investigated using a flocculent Saccharomyces cerevisiae, MA-R4, which has been recombinantly engineered to simultaneously co-ferment glucose and xylose to ethanol with high productivity. The flocculation level of MA-R4 dramatically decreased at pH values below 3.0 during co-fermentation of glucose and xylose. Sedimentation and microscopic observation revealed that flocculation was induced in MA-R4 when it fermented glucose, a glucose/xylose mixture, or mannose, whereas attempts to ferment xylose, galactose, and arabinose led to the loss of flocculation. MA-R4 fermented xylose and galactose more slowly than glucose and mannose. Therefore, the various flocculation behaviors shown by MA-R4 should be useful in the control of ethanol fermentation processes. 相似文献
A precise and accurate gas-liquid chromatographic (GLC) method has been developed for the quantitative analysis of the neutral sugars L-fucose (6-deoxygalactose), mannose, galactose, and glucose in ethanol precipitates of human serum proteins. The chromatographic conditions and sample preparation resulted in short analysis time (20 min per run) and made routine analyses practicable (twelve samples per day). The alditol acetate derivatization yielded single derivatives for each sugar. Complete separation was achieved on a 2.0 m X 2 mm I.D. column with 2.0% Silar-7CP on Chromosorb W AW 80--100 mesh. The results of hydrolysis showed that the release of fucose and galactose preceded the release of mannose. Hydrolysis with AG 50 W-X8 (H+) ion-exchange resin in 0.5 N HCl at 100 degrees for 7 h optimized glycosidic bond cleavage with only minimal destruction of fucose, mannose and galactose. A combination of strong cation- and anion-exchange resin columns was used to remove chromatographic background of peptides, amino acids, amino sugars, and inorganic ions. An average R.S.D. of less than 4% with recovery of greater than 86% for the three sugars was achieved. The homogeneity of the chromatographic peaks for the neutral sugars of normal human serum glycoproteins was confirmed by GLC--mass spectrometry. Significantly elevated ratios of fucose, galactose, and mannose to serum protein were observed for patients with small cell lung and ovarian carcinomas. 相似文献
The chemiluminescent reaction, in alkaline solution, of lucigenin with the reducing sugars sorbose, fructose, lactose, glucose, xylose, galactose, arabinose and mannose has been studied. There is a linear relationship (correlation coefficient = 0.996) between the emission intensity and the second-order rate constant for the alkaline oxidation of these sugars. The emission intensity is linearly related to the sugar concentration; at high sugar concentrations (5mM) it is independent of the lucigenin concentration, but at low concentrations (<0.05mM) is linearly related to the lucigenin concentration. These facts support the view that the rate-limiting step is the tautomerization of the sugars to the 1,2-enediol form; the enediol then undergoes reaction with lucigenin. 相似文献
The precise quantitative analysis of biomass sugars is a very important step in the conversion of biomass feedstocks to fuels
and chemicals. However, the most accurate method of biomass sugar analysis is based on the gas chromatography analysis of
derivatized sugars either as alditol acetates or trimethylsilanes. The derivatization method is time consuming but the alternative
high-performance liquid chromatography (HPLC) method cannot resolve most sugars found in biomass hydrolysates. We have demonstrated
for the first time that by careful manipulation of the HPLC mobile phase, biomass monomeric sugars (arabinose, xylose, fructose,
glucose, mannose, and galactose) can be analyzed quantitatively and there is excellent baseline resolution of all the sugars.
This method was demonstrated for standard sugars, pretreated corn stover liquid and solid fractions. Our method can also be
used to analyze dimeric sugars (cellobiose and sucrose). 相似文献
A quantitative approach was taken to determine the inhibition effects of glucose and other sugar monomers during cellulase
and β-Glucosidase hydrolysis of two types of cellulosic material: Avicel and acetic acid-pretreated softwood. The increased
glucose content in the hydrolysate resulted in a dramatic increase in the degrees of inhibition on both β-Glucosidase and
cellulase activities. Supplementation of mannose, xylose, and galactose during cellobiose hydrolysis did not show any inhibitory
effects on β-Glucosidase activity. However, these sugars were shown to have significant inhibitory effects on cellulase activity
during cellulose hydrolysis. Our study suggests that high-substrate consistency hydrolysis with supplementation of hemicellulose
is likely to be a practical solution to minimizing end-product inhibition effects while producing hydrolysate with high glucose
concentration. 相似文献
In this study, we determine concentrations of neutral and amino sugars and a sugar alcohol in freshwaters using high-performance liquid chromatography and pulsed amperometric detection with a single isocratic analysis. Coeluting arabinose, galactosamine, and mannosamine are separated with a mobile phase of 22.8 mM NaOH-KOH at a temperature of 17 degrees C. The resolutions are 0.73 and 0.64, respectively. The method separates closely eluting glucose-mannose and mannose-xylose peaks with resolutions of 0.85 and 0.71. Other sugars, fucose, rhamnose, galactose, fructose, ribose, glucosamine, and mannitol are resolved completely. Arabinose and galactosamine are measured in stream, ground, and soil waters that contain dissolved total saccharide (DTS) concentrations of 527 to 1555 nM. Failure to distinguish galactosamine from arabinose in those samples results in a 53-82% overestimation of arabinose concentrations and a 1.8-6.5% overestimation of DTS concentrations. The near unity of glucosamine and galactosamine concentrations in stream water samples allows us to suggest a correction factor for historical samples that had been analyzed without resolving galactosamine and arabinose. 相似文献
A polysaccharide with MW 25,000 consisting of arabinose, galactose, and mannose units in a 1:2.8:3.2 ratio was isolated from
Gleditsia macracantha seeds. Chemical and spectral methods established that the polysaccharide was a branched galactomannan with side branches
consisting of arabinose units.
Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 128-130, March-April, 2009. 相似文献
The process of converting renewable lignocellulosic biomass to ethanol requires a number of steps, and pretreatment is one
of the most important. Pretreatment usually in volves a hydrolysis of the easily hydrolyzed hemicellulosic component of biomass
using some form of thermal/chemical/mechanical action that results in a product that can be further hydrolyzed by cellulase
enzymes (the cellulosic portion). The sugars produced can then befermented to ethanol by fermentative microorganisms. If the
pretreatment step is not severe enough, the resultant residue is not as easily hydrolyzed by the cellulase enzyme. More severe
pretreatment conditions result in the production of degradation products that are toxic to the fermentative microorgan ism.
In this article, wereport the quantitative analysis of glucose, mannose, xylose, and acetic acid using Fourier transform infrared
(FTIR) spectroscopy on liquors from dilute-acid-pretreated softwood and hard wood slurries. Comparison of FTIR and high-performance
liquid chromatography quantitative analyses of these liquorsare reported. Recent developments in infrared probe technology
has enabled the rapid quantification of these sugars by FTIR spectroscopy in the batch reactor during optimization of the
pretreatment conditions, or interfaced to the computer controlling a continuous reactor for on-line monitoring and control. 相似文献
Astaxanthin is a potential high-value coproduct in an ethanol biorefinery. Three mutant strains of the astaxanthin-producing
yeast Phaffia rhodozyma, which were derived from the parent strain ATCC 24202 (UCD 67-210) and designated JTM166, JTM185, and SSM19, were tested
for their capability of utilizing the major sugars that can be generated from cellulosic biomass, including glucose, xylose,
and arabinose, for astaxanthin production. While all three strains were capable of metabolizing these sugars, individually
and in mixtures, JTM185 demonstrated the greatest sugar utilization and astaxanthin production. Astaxanthin yield by this
strain (milligrams astaxanthin per gram of sugar consumed) was highest for xylose, followed by arabinose and then glucose.
The kinetics of sugar utilization by strain JTM185 was studied in fermenters using mixtures of glucose, xylose, and arabinose
at varied concentrations. It was found that glucose was utilized preferentially, followed by xylose, and lastly, arabinose.
Astaxanthin yield was significantly affected by sugar concentrations. Highest yields were observed with sugar mixtures containing
the highest concentrations of xylose and arabinose. Hydrolysates produced from sugarcane bagasse and barley straw pretreated
by the soaking in aqueous ammonia method and hydrolyzed with the commercial cellulase preparation, Accellerase™ 1000, were
used for astaxanthin production by the mutant strain JTM185. The organism was capable of metabolizing all of the sugars present
in the hydrolysates from both biomass sources and produced similar amounts of astaxanthin from both hydrolysates, although
these amounts were lower when compared to yields obtained with reagent grade sugars. 相似文献
The gum exudate from Anacardium occidentale contains galactose (61 %), arabinose (14 %), rhamnose (7 %), glucose (8 %) and glucuronic acid (5 %) in addition to small amounts (<2 %) of each of mannose, xylose and 4-0 methylglucuronic acid. Contrary to earlier findings, the main aldobiuronic acid present is 6-O-(β-D-glucopyranosyluronic acid)-D-galactose; smaller amounts of the 4-O-methyl analogue are also present. Mild acid hydrolysis showed only two galactobioses, 3-O-β-D-galactopyranosyl-D-galactose (major component) and 6-O-β-D-galactopyranosyl-D-galactose (minor component). Degraded gum A, prepared by controlled acid hydrolysis, contained galactose, glucose, and uronic acid. A Smith-degradation of degraded gum A gave degraded gum B, which contained only galactose. Sequential Smith-degradations of Anacardium occidentale gum, and methylation analyses of the gum and of its degradation products indicated a highly-branched galactan framework consisting of chains of β-(1–3)-linked D-galactose residues branched and interspersed with β-(1–6) linkages. Arabinose is present as end-groups or in short (1–2)-linked chains up to five units long. Glucose, rhamnose, mannose xylose, and uronic acid are all present as end-groups. 相似文献
Three polysaccharides, LTPS-1, LTPS-21 and LTPS-31 were isolated and purified from the seed cakes of lacquer tree using DEAE-52 cellulose and Sephadex G-200 column chromatography. The total sugar contents of LTPS-1, LTPS-21 and LTPS-31 were 931.8, 958.2 and 895.1 g kg?1, respectively. LTPS-1 (3.48 kDa) was mainly composed of rhamnose, arabinose, glucose and galactose in a ratio of 35.36:5.06:1:2. LTPS-21 (11.4 kDa) was mainly composed of rhamnose, arabinose, mannose and galactose in a ratio of 41.93:21.8:1.01:9.24. LTPS-31 (19.49 kDa) was mainly composed of rhamnose, arabinose and mannose in a ratio of 38.31:16.44:1.1. IR analysis suggested they contained lower sulphuric acids, the LTPS-21 and LTPS-31 belonged to β-type polysaccharide. Among the three polysaccharides, LTPS-21 exhibited the strongest reducing power, scavenging activity on ABTS and hydroxyl radicals. These findings suggested that polysaccharides from the seed cakes could be potentially developed as natural functional ingredients in the food and cosmetic industry. 相似文献
Mixed fungal cultures used for making tempe, a fermented soy bean food, were screened for biomass conversion. Thirty-two zygomycetes strains from two tempe cultures were isolated and identified as Rhizopus, Mucor, Rhizomucor, and Absidia species based upon morphology. The dry weight biomass of these strains contained 49% to 63% protein and 10?C24% chitosan. The strains with the best growth performance were selected and registered at Culture Collection of Gothenburg University as Rhizomucor CCUG 61146 and Rhizomucor CCUG 61147. These strains were able to grow both aerobically and micro-aerobically. Their ethanol yields were 0.38?C0.47, 0.19?C0.22, and 0.31?C0.38?g/g on glucose, xylose, and a mix sugars consisting of cellobiose, glucose, xylose, arabinose, galactose, and mannose, respectively. The biomass yield of the strains varied between 65 and 140?mg dry weight/g glucose. 相似文献