Aqueous, High-Temperature Transformation of Carbohydrates Relative to Utilization of Biomass. Advances in Carbohydrate Chemistry and Biochemistry Volume 46. Elsevier; 1988. pp. 273-326. [DOI: 10.1016/s0065-2318(08)60169-9]

Dihydroxyacetone: A User Guide for a Challenging Bio-Based Synthon

1,3-dihydroxyacetone (DHA) is an underrated bio-based synthon, with a broad range of reactivities. It is produced for the revalorization of glycerol, a major side-product of the growing biodiesel industry. The overwhelming majority of DHA produced worldwide is intended for application as a self-tanning agent in cosmetic formulations. This review provides an overview of the discovery, physical and chemical properties of DHA, and of its industrial production routes from glycerol. Microbial fermentation is the only industrial-scaled route but advances in electrooxidation and aerobic oxidation are also reported. This review focuses on the plurality of reactivities of DHA to help chemists interested in bio-based building blocks see the potential of DHA for this application. The handling of DHA is delicate as it can undergo dimerization as well as isomerization reactions in aqueous solutions at room temperature. DHA can also be involved in further side-reactions, yielding original side-products, as well as compounds of interest. If this peculiar reactivity was harnessed, DHA could help address current sustainability challenges encountered in the synthesis of speciality polymers, ranging from biocompatible polymers to innovative polymers with cutting-edge properties and improved biodegradability.

Physical Properties of Hydrothermally Treated Rubberwood [Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg.] in Different Buffered Media

The dimensional instability of rubberwood [Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg.] is one of the major drawbacks that limits its utilization. Therefore, treatment is needed to improve these properties. Hydrothermal treatment in different buffered media is one of the techniques that improve its dimensional stability. The physical properties of hydrothermally treated rubberwood in different buffered media (pH 4, 6, 8, 10) and tap water (pH 7.43) with different temperatures (160 °C, 180 °C and 200 °C) were studied. In this study, physical properties such as equilibrium moisture content (EMC), density (ρ), mass loss (ML), water absorption (WA), volumetric swelling coefficient (VSC), thickness swelling (TS) and anti-swelling efficiency (ASE) were investigated for both treated and untreated specimens. Both the buffered media and temperature significantly affected the physical properties. The results indicated that the EMC (%), ρ (kg/m3), ML (%), VSC (%), TS (%) of treated rubberwood samples reduced as the treatment temperature increased. With the exception of WA (%), as WA increased when the treatment temperature increased from 160 °C to 180 °C but started to decrease when the temperature was further increased to 200 °C. The research study also exhibited that hydrothermal treatment using buffered media at different temperatures enhanced the dimensional stability of the treated samples. Alkaline media gave the best results on the physical properties compared to other treatment medias.

Ultrasensitive detection of pectin based on the decarboxylation reaction and surface-enhanced Raman spectroscopy

In the present study, a novel simple and sensitive method was developed for the determination of pectin based on the decarboxylation derivatization reaction and surface-enhanced Raman scattering (SERS) without complicated separation steps. The derivatization reaction can be controlled by the experimental parameters such as reaction time, temperature and the amount of hydrochloric acid. Additionally, the method was used to accurately and reliably detect pectin added in honey or apple, which can be detected at levels as low as 0.5 or 0.01 ppm, respectively. Based on the conventional decarboxylation reaction, a simple and sensitive SERS method was proposed for the detection of pectin, which shows potential for practical application.

Hydrothermal Modification of Wood: A Review

Wood is a versatile material that is used for various purposes due to its good properties, such as its aesthetic properties, acoustic properties, mechanical properties, thermal properties, etc. Its poor dimensional stability and low natural durability are the main obstacles that limit its use in mechanical applications. Therefore, modification is needed to improve these properties. The hydrothermal modification of wood exposes wood samples to elevated temperatures and pressure levels by using steam, water, or a buffer solution as the treating medium, or by using superheated steam. Abundant studies regarding hydrothermally treated wood were carried out, but the negative effect on the wood’s strength is one of the limitations. This is a method that boosts the dimensional stability and improves the decay resistance of wood with minimal decrements of the strength properties. As an ecofriendly and cost-effective method, the hydrothermal modification of wood is also a promising alternative to conventional chemical techniques for treating wood. Researchers are attracted to the hydrothermal modification process because of its unique qualities in treating wood. There are many scientific articles on the hydrothermal modification of wood, and many aspects of hydrothermal modification are summarized in review papers in this field. This paper reviews the hydrothermally modified mechanical properties of wood and their potential applications. Furthermore, this article reviews the effects of hydrothermal modification on the various properties of wood, such as the dimensional stability, chemical properties, and durability against termites and fungi. The merits and demerits of hydrothermal wood modification, the effectiveness of using different media in hydrothermal modification, and its comparison with other treating techniques are discussed.

Take Care in how you Store Your PD Fluids: Actual Temperature Determines the Balance between Reactive and Non-Reactive GDPs

Objective

During heat sterilization and during prolonged storage, glucose in peritoneal dialysis fluids (PDF) degrades to carbonyl compounds commonly known as glucose degradation products (GDPs). Of these, 3,4-dideoxyglucosone-3-ene (3,4-DGE) is the most cytotoxic. It is an intermediate in degradation between 3-deoxyglucosone (3-DG) and 5-hydroxymethyl-2-furaldehyde (5-HMF). We have earlier reported that there seems to be equilibrium between these GDPs in PDF. The aim of the present study was to investigate details of this equilibrium.

Methods

Aqueous solutions of pure 3-DG, 3,4-DGE, and 5-HMF were incubated at 40°C for 40 days. Conventional and low-GDP fluids were incubated at various temperatures for up to 3 weeks. Formaldehyde, acetaldehyde, glyoxal, methylglyoxal, 3-DG, 3,4-DGE, and 5-HMF were analyzed using high performance liquid chromatography.

Results

Incubation of 100 μmol/L 3,4-DGE resulted in the production of 36 μmol/L 3-DG, 4 μmol/L 5-HMF, and 40 μmol/L unidentified substances. With the same incubation, 200 μmol/L 3-DG was converted to 9 μmol/L 3,4-DGE, 6 μmol/L 5-HMF, and 14 μmol/L unidentified substances. By contrast, 100 μmol/L 5-HMF was uninfluenced by incubation. In a conventional PDF incubated at 60°C for 1 day, the 3,4-DGE concentration increased from 14 to a maximum of 49 μmol/L. When the fluids were returned to room temperature, the concentration decreased but did not reach original values until after 40 days. In a low GDP fluid, 3,4-DGE increased and decreased in the same manner as in the conventional fluid but reached a maximum of only 0.8 μmol/L.

Conclusions

Considerable amounts of 3,4-DGE may be recruited by increases in temperature in conventional PDFs. Lowering the temperature will again reduce the concentration but much more time will be needed. Precursors for 3,4-DGE recruitment are most probably 3-DG and the enol 3-deoxyaldose-2-ene, but not 5-HMF. Considering the ease at which 3,4-DGE is recruited from its pool of precursors and the difficulty of getting rid of it again, one should be extremely careful with the temperatures conventional PDFs are exposed to.

Glucose Degradation Products in Peritoneal Dialysis Fluids May Have Both Local and Systemic Effects: A Study of Residual Fluid and Mesothelial Cells

Objective

When peritoneal dialysis (PD) fluids are heat sterilized, glucose is degraded to carbonyl compounds. These compounds are known to interfere with many cellular functions and to promote the formation of advanced glycation end-products. However, little is known about what actually happens with glucose degradation products (GDPs) after infusion into the peritoneal cavity. The aim of the present study was to investigate possible targets for GDPs in the peritoneal cavity.

Design

In vitro reactions between residual fluid and GDPs were studied by incubating unused PD fluid with overnight dialysate. Confluent monolayer cultures of human mesothelial cells were used as a model to study the reactions of GDPs with the cells lining the peritoneal cavity.

Methods

Samples were analyzed, using high pressure liquid chromatography, for the presence of formaldehyde, acetaldehyde, 5-hydroxymethyl-2-furaldehyde (5-HMF), methylglyoxal, and 3-deoxyglucosone (3-DG). Cytotoxicity was determined as inhibition of proliferation of cultured fibroblasts.

Results

None of the analyzed GDPs reacted with overnight dialysate. Formaldehyde and methylglyoxal, in contrast to 3-DG and 5-HMF, reacted with the cultured mesothelial cells.

Conclusions

Low molecular weight carbonyls such as formaldehyde and methylglyoxal most probably react with the mesothelial cells lining the peritoneal cavity, and could be responsible for the disappearance of these cells during long-term treatment. 3-Deoxyglucosone showed remarkably low reactivity and was most probably transported within the patient.

Nitrogen-Functionalized Hydrothermal Carbon Materials by Using Urotropine as the Nitrogen Precursor

Nitrogen-containing hydrothermal carbon (N-HTC) materials of spherical particle morphology were prepared by means of hydrothermal synthesis with glucose and urotropine as precursors. The molar ratio of glucose to urotropine has been varied to achieve a continuous increase in nitrogen content. By raising the ratio of urotropine to glucose, a maximal nitrogen fraction of about 19 wt % could be obtained. Decomposition products of both glucose and urotropine react with each other; this opens up a variety of possible reaction pathways. The pH has a pronounced effect on the reaction pathway of the corresponding reaction steps. For the first time, a comprehensive analytical investigation, comprising a multitude of analytical tools and instruments, of a series of nitrogen-containing HTC materials was applied. Functional groups and structural motifs identified were analyzed by means of FTIR spectroscopy, thermogravimetric MS, and solid-state NMR spectroscopy. Information on reaction mechanisms and structural details were obtained by electronic structure calculations that were compared with vibrational spectra of polyfuran or polypyrrole-like groups, which represent structural motifs occurring in the present samples.

Kinetics of the conversion of dihydroxyacetone to methylglyoxal in New Zealand mānuka honey: Part II--Model systems

The irreversible dehydration reaction of dihydroxyacetone (DHA) to methylglyoxal (MGO) in a honey model system has been examined to investigate the influence of added perturbant species on the reaction rate. The secondary amino acid proline, primary amino acids (alanine, lysine and serine), and iron, or combinations of these perturbants, were added to artificial honey with either DHA or MGO and stored at 20, 27 and 37°C. These systems were monitored over time. A 1:1 conversion of DHA to MGO was not observed in any system studied, including the control system with no added perturbants. Addition of proline to the matrix increased consumption of DHA but did not produce any more MGO than the control sample. Lysine and serine behaved similarly. Alanine enhanced the conversion of DHA to MGO and had the best efficiency of conversion of DHA to MGO for the amino acids studied. An iron II salt enhanced the conversion of DHA to MGO, even in the presence of proline.

The role of activated charcoal in plant tissue culture

Activated charcoal has a very fine network of pores with large inner surface area on which many substances can be adsorbed. Activated charcoal is often used in tissue culture to improve cell growth and development. It plays a critical role in micropropagation, orchid seed germination, somatic embryogenesis, anther culture, synthetic seed production, protoplast culture, rooting, stem elongation, bulb formation etc. The promotary effects of AC on morphogenesis may be mainly due to its irreversible adsorption of inhibitory compounds in the culture medium and substancially decreasing the toxic metabolites, phenolic exudation and brown exudate accumulation. In addition to this activated charcoal is involved in a number of stimulatory and inhibitory activities including the release of substances naturally present in AC which promote growth, alteration and darkening of culture media, and adsorption of vitamins, metal ions and plant growth regulators, including abscisic acid and gaseous ethylene. The effect of AC on growth regulator uptake is still unclear but some workers believe that AC may gradually release certain adsorbed products, such as nutrients and growth regulators which become available to plants. This review focuses on the various roles of activated charcoal in plant tissue culture and the recent developments in this area.

Acid hydrolysis and quantitative determination of total hexosamines of an exopolysaccharide produced by Citrobacter sp

During the hydrolysis of an exopolysaccharide (EPS) produced by Citrobacter sp., the maximum liberation of hexosamine was obtained with 6 M HCl at 115 degrees C in an autoclave for 1 h. The glycosidic bond energy and degree of acetylation of the hexosamine in EPS were approximately 77 kJ mol(-1) and 61%, respectively. Thermal destruction of the hexosamines and the effect of salt on the hexosamine determination could be minimized under the optimized hydrolytic conditions. Using a modified Elson-Morgan method, maximum total hexosamine concentration was determined to be 3.2 g l(-1) (29% of crude EPS) after 96 h of fed-batch culture.

Generation of organic acids and monosaccharides by hydrolytic and oxidative transformation of food processing residues

Carbohydrate-rich biomass residues, i.e. sugar beet molasses, whey powder, wine yeast, potato peel sludge, spent hops, malt dust and apple marc, were tested as starting materials for the generation of marketable chemicals, e.g. aliphatic acids, sugar acids and mono-/disaccharides. Residues were oxidized or hydrolyzed under acidic or alkaline conditions applying conventional laboratory digestion methods and microwave assisted techniques. Yields and compositions of the oxidation products differed according to the oxidizing agent used. Main products of oxidation by 30% HNO(3) were acetic, glucaric, oxalic and glycolic acids. Applying H(2)O(2)/CuO in alkaline solution, the organic acid yields were remarkably lower with formic, acetic and threonic acids as main products. Gluconic acid was formed instead of glucaric acid throughout. Reaction of a 10% H(2)O(2) solution with sugar beet molasses generated formic and lactic acids mainly. Na(2)S(2)O(8) solutions were very inefficient at oxidizing the residues. Glucose, arabinose and galactose were formed during acidic hydrolysis of malt dust and apple marc. The glucose content reached 0.35 g per gram of residue. Important advantages of the microwave application were lower reaction times and reduced reagent demands.

Kinetic and chemical studies on the isomerization of monosaccharides in N-methylmorpholine-N-oxide (NMMO) under Lyocell conditions

The Lyocell process is a modern and environmentally fully compatible industrial fiber-making technology. Cellulosic pulp is dissolved without chemical derivatization in a melt of N-methylmorpholine-N-oxide monohydrate (NMMO). In the present work, the reactions of monosaccharides under Lyocell conditions were investigated in detail, using capillary zone electrophoresis as the analytical technique to clarify the composition of reaction mixtures and to follow the kinetics. Under Lyocell conditions, xylose and glucose undergo two competitive reactions: rapid conversion to nonreducing products, and complete isomerization involving the whole carbohydrate backbone, via ketose intermediates. Sugar acids are present in minor amounts only, as demonstrated by employing isotopically labeled material for NMR techniques.

Study of degradation pathways of Amadori compounds obtained by glycation of opioid pentapeptide and related smaller fragments: stability, reactions, and spectroscopic properties

Reactions between biological amines and reducing sugars (the Maillard reaction) are among the most important of the chemical and oxidative changes occurring in biological systems that contribute to the formation of a complex family of rearranged and dehydrated covalent adducts that have been implicated in the pathogenesis of human diseases. In this study, chemistry of the Maillard reactions was studied in four model systems containing fructosamines (Amadori compounds) obtained from the endogenous opioid pentapeptide leucine-enkephalin (Tyr-Gly-Gly-Phe-Leu), leucine-enkephalin methyl ester, structurally related tripeptide (Tyr-Gly-Gly), or from amino acid (Tyr). The degradation of model compounds as well as their ability to develop Maillard fluorescence was investigated under oxidative conditions in methanol and phosphate buffer pH 7.4 at two different temperatures (37 and 70 degrees C). At 37 degrees C, glycated leucine-enkephalin degraded slowly in methanol (t(1/2) approximately 13 days) and phosphate buffer (t(1/2) approximately 9 days), producing a parent peptide compound as a major product throughout a three-week incubation period. Whereas fluorescence slowly increased over time at 37 degrees C, incubations off all studied Amadori compounds at 70 degrees C resulted in a rapid appearance of a brown color and sharp increase in AGE (advanced glycation end products)-associated fluorescence (excitation 320 nm/emmision 420 nm) as well as in distinctly higher amounts of fragmentation products. The obtained data indicated that the shorter the peptide chain the more degradation products were formed. These studies have also helped to identify a new chemical transformation of the peptide backbone in the Maillard reaction that lead to beta-scission of N-terminal tyrosine side chain and p-hydroxybenzaldehyde formation under both aqueous and nonaqueous conditions.

Degree of acetylation of heteropolysaccharides

The acetyl groups in polysaccharides and glycoproteins have been determined using 4 N HCl at 120 degrees C for acid hydrolysis. Acetic acid and hexosamine were determined by high-performance cation-exchange chromatography with UV detection and high-performance anion-exchange chromatography with pulsed amperomeric detection, respectively. The method compares well with other procedures and shows an additional advantage of being able to analyze for hexosamine in the same hydrolyzate, thus permitting the degree of acetylation of hexosamine-containing biopolymers to be determined directly without correction for additional components in the material of interest.

The role of deoxyhexonic acids in the hydrothermal decarboxylation of carbohydrates

Hydrothermolysis of D-glucose, cellobiose, and beta-cyclodextrin leads to the formation of small amounts of 3-deoxyhexonic acids. These acids are known to be produced by the alkaline degradation of carbohydrates. The formation under neutral hydrothermal conditions of the 3-deoxyhexonic acids provides evidence for the formation of 3-deoxy-D-erythro-hex-2-ulose, a compound that has been reported to play a role in both alkaline and acidic conversion of carbohydrates. Hydrothermolysis of 2- and 3-deoxy-D-arabino-hexonic acid does not lead to significant decarboxylation, and therefore these compounds cannot be considered to play a major role in the initial hydrothermal decarboxylation of biomass.

Autoclaved and filter sterilized liquid media in maize anther culture: significance of activated charcoal

Medium sterilization techniques (autoclaving, filter sterilization and separate sterilization of medium components), combined with preculture exposure to activated charcoal (AC) were evaluated for effects on maize anther culture response. The addition of AC to filter sterilized medium had no effect on the number of embryo-like-structures (ES) produced. For autoclaved medium, pre-culture AC treatment resulted in a 3-fold increase in ES yield over medium lacking AC. When AC was included, autoclaved medium was more productive than filter sterilized medium. Autoclaved media without AC gave lower response than filter sterilized medium. Separate sterilization of sucrose or FeEDTA was beneficial for media autoclaved in the absence of AC. However, when all components were autoclaved together in the presence of AC, there was no advantage to separate sterilization. The maximum ES frequency (224.6 ES/100 anthers) was obtained with the genotype ETH-M 52 cultured in autoclaved medium which had been exposed to AC (5 g/L) for 96 h prior to culture initiation. It is supposed that the higher ES frequencies observed with AC-treated, autoclaved media were due to the availability of glucose and fructose following heat-induced hydrolysis of sucrose and the AC-mediated adsorption of inhibitory compounds produced during autoclaving.

Diagnostic methods for the determination of iduronic acid in oligosaccharides

A high-performance liquid chromatography (HPLC) method with pulsed amperometric detection (PAD) was used for the determination of the acid hydrolysis products of L-iduronic acid containing oligosaccharides isolated from biological sources. This HPLC-PAD method was compared with gas chromatographic (GLC) methods. Since acid hydrolysis of oligosaccharides can produce a number of products, several uronic acid derivatives were prepared by chemical synthesis. These well characterized standards in conjunction with mass spectrometry allowed for the identification of most of the products of methanolysis or hydrolysis of glycosamino-glycans, which included chondroitin sulfates A and B (dermatan sulfate), heparin, and hyaluronic acid. (4 M) HCl in methanol 100 degrees C for 24 h was found to be optimum for GLC and 1 M aqueous HCl for 4 h at 100 degrees C for HPLC-PAD. All of the monosaccharides, hexosamines, and uronic acids could be separately identified in a single chromatographic step using either technique. Good resolution, high sensitivity (low microgram samples) and rapid analysis makes these methods particularly useful for the determination of small amounts of glycosaminoglycans and other glycoconjugates found in samples isolated from biological sources. These two techniques are specifically designed to allow the qualitative determination of the carbohydrate content and composition of samples whose carbohydrate composition and content is completely unknown.

Further studies on the mechanism of phenol-sulfuric acid reaction with furaldehyde derivatives

Even though the chromogens formed from mannose and galactose showed comparable absorbances at 480 nm in the conventional (developer present during heat of dilution) and modified (developer reacted at room temperature after cooling; epsilon mannose = 13,700, galactose = 14,000) phenol-sulfuric acid reactions, shoulders in the region 420-430 nm were prominent in the former method. Fucose was 10 times less reactive in the modified method (epsilon = 800) than in the conventional method. 2-Formyl-5-furan sulfonic acid reacted equally efficiently in the two methods (epsilon = 40,800). 5-Methyl-2-furaldehyde, unlike the sulfonate derivative or 5-hydroxymethyl-2-furaldehyde, required heat for condensation with phenol. 2-Furaldehyde dimethylhydrazone reacted 25 times better to form a chromogen (epsilon = 40,500) in the modified phenol-sulfuric acid method. The possible roles of intermediates between hexoses and furaldehydes in forming chromogens and the effect of substitution at the 2- and 5-positions of furaldehyde on the rates of condensation with phenol for the observed differences between the conventional and the modified methods are discussed.