Ultrahigh-performance liquid chromatography coupled with evaporative light scattering detector was used to optimize acid hydrolysis conditions of polysaccharides from Dendrobium candidum. The optimized conditions were the concentration of H2SO4, 0.4?M, hydrolysis temperature, 90°C, and hydrolysis time, 1?h. Ultrahigh-performance liquid chromatography-quadrupole time-of-flight mass spectrometry was used to obtain the total ion current chromatograms and determine the hydrolyzates of polysaccharides, such as monosaccharides, oligosaccharides, and some low-molecular weight polysaccharides from D. candidum, Cordyceps sinensis, and Ganoderma atrum. The accurate mass data were analyzed by chemometric tools, including an unsupervised analytical method, principal component analysis (one-way ANOVA, p?D. candidum polysaccharides from different locations and grades can be discriminated effectively by the principal component analysis scores. The quality predictive models showed a high value with a low prediction error calculated from both validation and training sets. 相似文献
A low, but significant, fraction of the carbohydrate portion of herbaceous biomass may be composed of fructose/fructosyl-containing
components (“fructose equivalents”); such carbohydrates include sucrose, fructooligosaccharides, and fructans. Standard methods
used for the quantification of structural-carbohydrate-derived neutral monosaccharide equivalents in biomass are not particularly
well suited for the quantification of fructose equivalents due to the inherent instability of fructose in conditions commonly
used for hemicellulose/cellulose hydrolysis (>80% degradation of fructose standards treated at 4% sulfuric acid, 121°C, 1 h).
Alternative time, temperature, and acid concentration combinations for fructan hydrolysis were considered using model fructans
(inulin, β-2,1, and levan, β-2,6) and a grass seed straw (tall fescue, Festuca arundinacea) as representative feedstocks. The instability of fructose, relative to glucose and xylose, at higher acid/temperature combinations
is demonstrated, all rates of fructose degradation being acid and temperature dependent. Fructans are shown to be completely
hydrolyzed at acid concentrations well below that used for the structural carbohydrates, as low as 0.2%, at 121°C for 1 h.
Lower temperatures are also shown to be effective, with corresponding adjustments in acid concentration and time. Thus, fructans
can be effectively hydrolyzed under conditions where fructose degradation is maintained below 10%. Hydrolysis of the β-2,1
fructans at temperatures ≥50°C, at all conditions consistent with complete hydrolysis, appears to generate difructose dianhydrides.
These same compounds were not detected upon hydrolysis of levan, sucrose, or straw components. It is suggested that fructan
hydrolysis conditions be chosen such that hydrolysis goes to completion; fructose degradation is minimized, and difructose
dianhydride production is accounted for. 相似文献
The method for preparing low molecular weight fucosylated chondroitin sulfate from sea cucumber Isostichopus badionotus using partial acid hydrolysis was reported, and its hydrolysis mechanism was also investigated. The sea cucumber chondroitin sulfate FCS was hydrolyzed under different conditions (80 ℃ 3 h and 6 h), then isolated and purified on a Bio-P-4 geltration to prepare low molecular weight fractions (LMWF-FCS). The chemical compositions of LMWF-FCS showed the branched fucose (Fuc) was cleaved during acid hydrolysis process, whereas the mole ratio of acetyl-galactosamine (GalNAc) and glucuronic acid (GlcA) in the backbone remained the same, which indicated the backbone was a typical chondroitin sulfate structure. The disaccharide composition analysis of LMWF-FCS suggested that the sulfation patterns of GalNAc in the backbone chain changed and the substitution value was reduced. Furthermore, the 1 D NMR analysis illustrated the branched-Fuc was cleaved during acid hydrolysis, but their substitution patterns were not influenced, which was distinct from the previous reports that the substitutions of branched-Fuc in FCS were easy to change. Simultaneously, the sulfation pattern of GalNAc in backbone chain changed obviously in the acid hydrolysis process. The anticoagulant activity in vitro illuminated the anticoagulant activity of the degradation products over time in the acid hydrolysis are gradually declined, but still kept good. Therefore, the LMWF-FCS prepared could be developed as a new anticoagulant and antithrombotic drug like low molecular weight heparin. 相似文献
Sugarcane bagasse, a byproduct of the cane sugar industry, is an abundant source of hemicellulose that could be hydrolyzed
to yield a fermentation feedstock for the production of fuel ethanol and chemicals. The effects of sulfuric acid concentration,
temperature, time, and dry matter concentration on hemicellulose hydrolysis were studied with a 20-L batch hydrolysis reactor
using a statistical experimental design. Even at less severe conditions considerable amounts (>29%) of the hemicellulose fraction
could be extracted. The percentage of soluble oligosaccharides becomes very low in experiments with high yields in monosaccharides,
which indicates that the cellulose fraction is only slightly affected. For the sugar yields, acid concentration appears to
be the most important parameter, while for the formation of sugar degradation products, temperature shows the highest impact.
It could be demonstrated that the dry matter concentration in the reaction slurry has a negative effect on the xylose yield
that can be compensated by higher concentrations of sulfuric acid owing to a positive interaction between acid concentration
and dry matter contents. 相似文献
The hydrolysis of PEtOx is studied to evaluate the potential toxicity of partially hydrolyzed polymers that might interfere with its increasing popularity for biomedical applications. The hydrolysis of PEtOx is studied in the presence of digestive enzymes (gastric and intestinal) and at 5.8 M hydrochloric acid as a function of temperature (57, 73, 90, and 100 °C). It is found that PEtOx undergoes negligible hydrolysis at 37 °C and that thermal and solution properties are not altered when up to 10% of the polymer backbone is hydrolyzed. Mucosal irritation and cytotoxicity is also absent up to 10% hydrolysis levels. In conclusion, PEtOx will not decompose at physiological conditions, and partial hydrolysis will not limit its biomedical applications.
Beech wood derived xylan to hydrolyzed to predominantly xylose monomer units after exposure to hot, compressed liquid water
saturated with carbon dioxide. Similar treatment without CO2 saturation resulted in only minor hydrolysis and a smaller fraction of monomers among the hydrolysis products. Severity of
the hydrolysis reaction was correlated to reaction time, temperature, and carbon dioxide partial pressure and followed a function
similar to those used to characterize mineral acid systems. Results from parallel hydrolysis experiments with an aqueous system
and a very dilute sulfuric acid system allowed an approximation of the dissociation constant of carbonic acid in the temperature
range of 170–230°C. Results suggest that carbonic acid may be a viable reagent for promoting hydrolysis without mineral acids,
especially in the case of a bioprocessing plant that produces carbon dioxide. 相似文献
