Hexose Fractions Research Articles

Novel Challenges on the Catalytic Synthesis of 5-Hydroxymethylfurfural (HMF) from Real Feedstocks

The depletion of fossil resources makes the transition towards renewable ones more urgent. For this purpose, the synthesis of strategic platform-chemicals, such as 5-hydroxymethylfurfural (HMF), represents a fundamental challenge for the development of a feasible bio-refinery. HMF perfectly deals with this necessity, because it can be obtained from the hexose fraction of biomass. Thanks to its high reactivity, it can be exploited for the synthesis of renewable monomers, solvents, and bio-fuels. Sustainable HMF synthesis requires the use of waste biomasses, rather than model compounds such as monosaccharides or polysaccharides, making its production more economically advantageous from an industrial perspective. However, the production of HMF from real feedstocks generally suffers from scarce selectivity, due to their complex chemical composition and HMF instability. On this basis, different strategies have been adopted to maximize the HMF yield. Under this perspective, the properties of the catalytic system, as well as the choice of a suitable solvent and the addition of an eventual pretreatment of the biomass, represent key aspects of the optimization of HMF synthesis. On this basis, the present review summarizes and critically discusses the most recent and attractive strategies for HMF production from real feedstocks, focusing on the smartest catalytic systems and the overall sustainability of the adopted reaction conditions.

EVALUATION OF METABOLISM PARAMETRES OF CONNECTIVE TISSUE IN TREATMENT OF EXPERIMENTAL PURULENT WOUNDS OF CATS

Wound pathology is one of the most important problems of modern veterinary surgery. Violation of connective tissue metabolism significantly affects occurrence and development of many pathological processes in various organs and tissues, however, parametres of connective tissue metabolism in purulent wounds of cats have not been thoroughly studied. Therefore, their study will allow to substantiate pathogenetically and improve treatment methods of purulent wounds of cats. The studies were carried out from 2010 to 2020 on the basis of the clinic of veterinary medicine and the laboratory of the Department of Surgery and Diseases of Small Animals of Luhansk State Agrarian University, as well as in biochemical and immunological laboratory of Lugansk. Twelve animals were used in the experiment, which were divided into two groups (the first - experimental, the second - control). The ointment "Methyluracil with Miramistin" (Darnitsa) with addition of 1% hyaluronic acid and 1% trifusol were used in the experimental group. Only "Methyluracil with Miramistin" ointment was used for treatment of animals in the control group. Animals underwent daily revision of wounds and local mechanical treatment. For planimetric studies, a ruler and a transparent film with a grid on it with a cell size of 1 cm2 were used. As for animals of the experimental group, content increase of hexoses associated with proteins, hexoses of glycoproteins and sialic acids was recorded only during the period of inflammatory and degenerative changes. Subsequently, starting from the 12th day of the experiment, these parametres decreased to the initial level. As for animals of the control group, the content of hexoses associated with proteins gradually decreased, but was higher than that of cats of the experimental group due to increase of hexoses of glycosaminoglycans. Also, the content of sialic acids in the control group remained high throughout the experiment. Such tendency indicates that application of ointment with addition of hyaluronic acid and trifusol contributes to normalization of the H-GAG / H-GP index, which is typical for a more intensive development of reparative processes. On the contrary, an increase of the healing time of a wound defect of animals of the control group was accompanied by a redistribution of hexose fractions towards an increase in the proportion of glycosaminoglycans. These changes are stipulated by gradual depolymerization and restructuring of the basic substance of the connective tissue in the phase of regeneration and proliferation of the wound process.

ПАТОГЕНЕТИЧЕСКИЕ ПОДХОДЫ К ТЕРАПИИ ПРИ ЭКСПЕРИМЕНТАЛЬНЫХ ИНФИЦИРОВАННЫХ РАНАХ У КОШЕК

Wound pathology is one of the most important problems of modern veterinary surgery. Violation of connective tissue metabolism significantly affects the occurrence and development of many pathological processes in various organs and tissues, but the indicators of connective tissue metabolism in purulent wounds in cats have not been studied enough. Therefore, their study will allow pathogenetically substantiate and improve the methods of treatment of purulent wounds in cats. In animals of the experimental group who were treated with methyluracil with miramistin with the addition of 1% hyaluronic acid and 1% trifuzol, an increase in the content of hexoses associated with proteins, hexoses of glycoproteins and sialic acids was recorded only during the period of inflammatory and degenerative changes. In the future, starting from the twelve days of the experiment, these indicators decreased to the initial level. In animals of the control group during treatment, the content of hexoses associated with proteins gradually decreased, but was higher than in cats of the experimental group due to an increase in the proportion of hexoses of glycosaminglicans. Also in the control group, the content of sialic acids remained high throughout the experiment. This trend indicates that the use of ointment with the addition of hyaluronic acid and trifuzol contributes to the normalization of the G-GAG / G-GP index, which is characteristic of a more intensive development of reparative processes. On the contrary, an increase in the healing time of a wound defect in animals of the control group was accompanied by a redistribution of hexose fractions towards an increase in the proportion of glycosaminglicans. These changes are due to the gradual depolymerization and restructuring of the main substance of the connective tissue in the phase of regeneration and proliferation of the wound process.

A Mathematical Model to Evaluate the Kinetics of D-glucose and D-fructose Fermentations by Saccharomyces bayanus at Increasing Ethanol Concentrations

In the cellar, slow and stuck fermentations occurring during winemaking are often successfully solved by the addition of yeast strains like Saccharomyces bayanus. The kinetic behaviour shown by S. bayanus during alcoholic fermentation was investigated using a mathematical model previously tested for S. cerevisiae, in order to show which of the six functional parameters of the model differed significantly with the yeast population. Although some parameters (hexose fractions converted to ethanol and glycerol) did not change, the kinetic constant related to the inactivation rate of the yeast population showed by S. cerevisiae assumed a value significantly higher (approximately 50-fold) than that observed for S. bayanus, while this latter population was ten times less affected by ethanol than S. cerevisiae. Although no remarkable differences could be found between the ability shown by the two yeast populations to convert hexoses (D-glucose and D-fructose), the tolerance for ethanol accumulation changed strongly. The conversion rate of these two hexoses by S. bayanus was affected less (about ten thousand-fold) by ethanol than that of S. cerevisiae.

Batch fermentation kinetics of ethanol production by Zymomonas mobilis on cellulose hydrolysate

Growth and ethanol production by three strains (MSN77, thermotolerant, SBE15, osmotolerant and wild type ZM4) of the bacterium Zymomonas mobilis were tested in a rich medium containing the hexose fraction from a cellulose hydrolysate (Aspen wood). The variations of yield and kinetic parameters with fermentation time revealed an inhibition of growth by the ethanol produced. This inhibition may result from the increase in medium osmolality due to ethanol formation from glucose.

Alcoholic fermentation of cellulose hydrolysate by Zymomonas mobilis

Growth and ethanol production by three strains of the bacterium Zymomonas mobilis were tested, at 40°C, in a medium containing cellulose hydrolysate (hexose fraction) as carbon source. The thermotolerant mutant C107 exhibited the best growth compared to wild type ZM4 and to the osmotolerant mutant SBE15. When cultivated in media supplemented with various nutrients, growth was only observed in presence of yeast extract (10 g/l) which acted both as a vitamin supplier and pH stabilizer. Using calcium pantothenate instead of yeast extract and sodium acetate to control pH resulted in growth inhibition by the high medium osmolality. Batch fermentation with pH control (KOH addition) showed good growth and ethanol production with the mineral medium.

Sugar transport in leaf discs ofPhaseolus coccinius

Kinetic profiles for sucrose, glucose and 3‐OMG glucose were determined in leaf discs ofPhaseolus cocciniusL. (cv. Scarlet). All three sugars exhibited identical uptake kinetics. At sugar concentrations below 25 mM, transport was due to an active, carrier‐mediated transport system. A linear component was the dominant mode of uptake at sugar concentrations above 25 mM. Sucrose and glucose carriers were specific for these sugars, since no uptake inhibition was observed from competing sugars. Sucrose was not hydrolyzed by leaf tissue because the label in asymetrically labeled sucrose was not randomized. Furthermore, no label was present in hexose fractions when tissue was incubated with [84C]‐sucrose. Therefore, [14C]‐sucrose uptake did not reflect hexose uptake.Both saturable and linear components of uptake contribute significantly to total uptake rates. The former, however, is more important when apoplastic sugar concentrations are low. The molecular nature of the linear component is not well understood but accounts for most of the uptake at high sugar concentrations.

Solute Accumulation by Grape Pericarp Cells III. Sugar Changes in vivo and the Effect of Shading

Summary The endogenous glucose, fructose and sucrose of the skin of the grape berry has been partitioned into diffusible and residual fractions during 1G d of the phase of rapid sugar accumulation following veraison. The data have been related to total soluble solids of the perirarp juice (°Brix) as an index of development: strong correlations were found between the partitioned hexose fractions and 0 Brix, but with the notable exception of non-diffusing glucose which was most variable during this period. Sucrose did not show good correlations with other attributes. A large proportion of both glucose and fructose diffused from the skin into an osmotic buffer during 30 min of efflux: at 5 °Brix, 40—45% of each hexose diffused, and at 16 °Brix this fraction was 70 to 75%. However, the degree of eompartmentation of glucose consistently exceeded that of fructose by a small, constant amount for any given total level. A series of berries were shaded individually, a treatment known to lessen the rate of global sugar accumulation but, as shown here, having no qualitative effect upon the relationship between glucose and fructose nor upon their degrees of “compartmentation”. A tentative calculation indicates a substantial concentration gradient between the diffusible and compartmented space (compartmented space having the lower concentration) both before veraison and during rapid sugar accumulation in the tissue. Aceumulation seems essentially an increase in diffusible sugars, in whir h the primary process is probably unloading from the phloem into the apoplast rather than eventual compartmentation within the cell.

Occurrence of an organic inhibitor in cane molasses affecting citric acid production by Aspergillus niger

A highly potent inhibitor of citric acid fermentation by Aspergillus niger is shown to be present, in addition to minerals, in cane molasses. Sephadex G-10 fractionation of molasses shows the inhibitor to be present in the hexose fraction. This fraction, after concentration reduces the citric acid yield from a citric acid-producing system. The hexose fraction of the sulphitated syrup is much more inhibitory than the hexose fraction of unsulphitated syrup, indicating enhanced activity of the inhibitor at this step of cane-juice processing in sugar-mills.

Thermophilic ethanol fermentations.

Thermophilic ethanol fermentations are of interest to industrial alcohol production because both the pentose and hexose fraction of biomass can be directly fermented in high yield (i.e., mol ethanol/mol substrate consumed), and because of potential novel process features associated with high temperature operation. As a net result, the co-culture cellulose fermentations described here may have the potential to convert more substrate to alcohol than some other bioconversion systems described [see Figure 11, (2)]. However, considerably more fundamental and applied research is required before realistic economic assessments can be made. Detailed analysis of the data presented above suggests key control parameters for thermophilic ethanol production (see Table IX). Understanding in detail the physiological and biochemical features that control rate limitation, yield limitation and concentration limitation appears to me as trends for future applied and fundamental studies on thermophilic ethanologenic bacteria. It is worth noting from the data reviewed here that understanding control of any one of these 3 major limitations is complex and multi-faceted. Indeed, improvement of ethanol tolerance (i.e. the ability to produce greater than 1% ethanol at high rates) in these bacteria appears to involve challenges by all three limitations. Furthermore, the biochemical basis for alcohol tolerance in thermophilic ethanologens appears to vary in different species. For example, the ethanol dehydrogenase of C. thermocellum is inhibited by physiological concentrations of alcohol (i.e. 1%) whereas, the reversible activity of T. brockii or C. thermohydrosulfuricum enzyme is increased by higher solvent concentration (greater than 5%).

Hexosamine metabolism II. effect of insulin and phlorizin on the absorption and metabolism, in vivo, of d-glucosamine and [formula omitted] in the rat

1. 1. Fasted rats, which had been treated with neomycin and injected with insulin or phlorizin, were administered solutions containing either d-[1- 14C]glucosamine or N- acetyl- d -[1- 14 C] glucosamine by stomach tube. 2. 2. Insulin did not affect the absorption coefficients of glucosamine or N-acetyl-glucosamine. The production of 14CO 2, as a per cent of that absrobed, from d-[1- 14C]-glucosamine was almost doubled in rats treated with insulin, but the increase was less marked in those given N- acetyl- d -[1- 14 C] glucosamine . Insulin increased significantly the specific radiactivity of the hexose fraction of liver and small-intestinal tissue from rats administered d-[1- 14C]glucosamine or N- acetyl- d -[1- 14 C] glucosamine . There results are consistent with the hypothesis that insulin may alter in some tissues the cellular transport or metabolism of these amino sugars. 3. 3. Pholorizin stimulated the adsorption of glucosamine and markedly inhibited the absorption of N-acetyglucosamine. The percentage of absorbed radioactivity incorporated into the non-dialyzable fraction of serum from both amino sugars was increased. Pholorizin also increased significantly the dialyzable radioactivity of the small-intestinal tissue in rats administered N-acetylglucosamine but not glucosamine. Although the amounts of hexosamine, hexose and amino acid in the small intestinal tissues were not altered by pholorizin, the specific radioactivities of these fractions from the group of rats given N-acetylglucosamine were increased. These results suggest that pholorizin may alter the transport of N-acetylgucosamine and also its metabolism to non-dialyzable or macromolecular tissue hexosamine.

Incorporation of radioactive glucosamine into submicrosomal fractions isolated from rat liver

The incorporation of [1- 14C[glucosamine into various submicrosomal fractions and cell sap from rat liver, as well as into plasmaproteins, has been examined after intraperitoneal injection. It has been shown that after 1 h there is a significant incorporation of protein-bound radioactivity into the submicrosomal fractions. 69% of the total radioactivity was found in the ultrasonic extract of the microsomal pellet, 28% in the subsequent deoxycholate extract and 3% associated with the ribosomes. Of the total radioactivity in the ultrasonic extract and the deoxycholate extract, more than 80% was found in the perchloric acid precipitate and only about 5–10% in the phosphotungstic acid precipitate. 15% of the protein-bound radioactivity in the perchloric acid precipitate of the ultrasonic extract was associated with a sialic acid fraction and about 1% found in the hexose fraction. Most of the remaining radioactivity was associated with glucosamine. The intracellular site for the biosynthesis of glycoproteins is discussed.

Effect of Age on Growth and Metabolism of Mycelial Felts ofRhizoctonia solani

The results of the present investigation showed that the five-day-old mycelial mats of Rhizoctonia solani revealed least but steady rate of respiration, smallest sugar uptake, and maximum efficiency in building up and accumulation of carbo hydrates within their mats. They were thus considered to be most suitable for studies on growth and metabolism. The fungus used in the present investigation was R. solani Kuhn. The fungus was grown throughout the whole work on a modified Richard's culture medium. The methods used for the preparation and extraction of mycelial mats and estimation of various sugars in the culture media or mycelial mats, C02-output and pH-values were those described by Tolba and Salama (1961). RESULTS AND DISCUSSION (a) Analysis of media. The results of the analysis of the various media for their sugar contents are represented graphically in Fig. 1. This shows that all the sucrose media started with a very low direct reducing value. When coming in contact with the fungal mats, reducing sugars (in the forms of glucose and fructose) accumulated in the culture media. This result indicated sucrose inversion into glucose and fructose in culture media of the test mats, thus fully confirming the previous finding by Said and Naguib (1955). Analysis of the culture media for their various hexose fractions showed that they invariably contained less amounts of glucose than fructose throughout