Fructose mannitol formation

Addition of some sodium borate to increase the fructose —> mannitol hydrogenation selectivity due to fructose-borate complex formation [21, 22]. 

Mannitol salt formation is also used as a laboratory diagnostic test for the separation of homofermenters (which do not reduce fructose in formation of mannitol) from heterofermenters, which utilize the pathway described above. From the winemaker s perspective, the importance of mannitol formation, by itself, is uncertain except to increase the potential for acetic acid production. Sponholz (1993) reports that it is associated with bacterially mediated deterioration in high-pH sweet wines. He concludes that the best technique for the prevention is acidulation, whereby the pH is lowered to the point (<3.5) at which the likelihood of growth of most spoilage lactics is precluded. 

Oxidation of mannitol Formation of fructose (used by yeasts and LAB)... 

In 1886, Brown11 discovered an organism which formed extremely tough membranes when cultivated m suitable nutrient solutions containing carbohydrates such as D-fructose, D-mannitol or D-glucose ethanol, sucrose or starch did not support membrane formation by this organism which Brown called Bacterium xylinum ) (Acetobacter xylinum). The membranes were readily soluble in cuprammonium hydroxide solution and yielded a dextrorotatory sugar upon acid hydrolysis. These properties and the results of combustion analysis led him to believe that the membrane was cellulose. 

Normally, however, the reaction involving the formation of hydroxy-methylfurfural proceeds less readily than does the hydrogenation of glucose and fructose to mannitol and sorbitol, but its occurrence is detected by the fact that tetrahydrofuran derivatives have been isolated from the hydrogenation products. Thus, we have isolated tetrahydrofuran 2,5-dicarbinol (identified as its ditosyl derivative), 5-methyltetra-hydrofurfuryl alcohol and 2,5-dimethyltetrahydrofuran (VII) together with hydrogenolysis products of these compounds. 

The first, total synthesis of sugar-like compounds was performed as early as 1861 in that year, Butlerov2 reported the formation of methylenitan on treatment of aqueous formaldehyde with calcium hydroxide. The first, defined sugar derivative, DL-mannitol ( a-acrit ), was obtained by Emil Fischer and Tafel,3 and the first, optically active, totally synthetic sugars, D- and L-mannose and D- and L-fructose, were also prepared by Fischer.4... 

MPa H2. To suppress the isomerization of D-glucose to D-mannose and D-fructose (Lobry de Bruyn-van Ekenstein transformation) (Scheme 5.2) and the Cannizzaro reaction, which were both promoted in an alkaline medium, the pH value was maintained between 5.5 and 6.5. Under the conditions that were optimized to minimize the side reactions, the formation of gluconic acid and mannitol was reduced to less than 1% each at 99.5-99.6% conversion, while with a normal nonpromoted Raney Ni 1.5-2.1% of gluconic acid and 1.3-1.9% of mannitol were formed at 99.5-99.7% conversion. 

The formation of alditols in eye lenses is one of the major complications in diabetic patients. Interestingly, the detailed molecular pattern of the lens alditols allows us to differentiate between the diabetic lens having increased concentrations of sorbitol 3-phosphate and fructose 3-phosphate, and the galactosemic lens, where the major products are galactitol 2-phosphate and galactitol 3-phosphate [202]. 2,5-Anhydro-D-mannitol is an analogue of fructose that has become popular in cellular metabolic studies using perfused rat liver [203]. 

D-mannitol is widely used as sweetening agent and finds also different application in the food industry and related areas [1]. D-mannitol can be directly prepared from mannose or by stereoselective hydrogenation of D-fructose. However, the hydrogenation of D-fructose in aqueous solution over different heterogeneous catalysts leads to the formation of two isomers, i.e. D-mannitol and D-sorbitol, near to a ratio of one to one [1]. 

A study of the relaxational transitions and related heat capacity anomalies for galactose and fructose has been described which employs calorimetric methods. The kinetics of solution oxidation of L-ascorbic acid have been studied using an isothermal microcalorimeter. Differential scanning calorimetry (DSC) has been used to measure solid state co-crystallization of sugar alcohols (xylitol, o-sorbitol and D-mannitol), and the thermal behaviour of anticoagulant heparins. Thermal measurements indicate a role for the structural transition from hydrated P-CD to dehydrated P-CD. Calorimetry was used to establish thermodynamic parameters for (1 1) complexation equilibrium of citric acid and P-CD in water. Several thermal techniques were used to study the decomposition of p-CD inclusion complexes of ferrocene and derivatives. DSC and derivative thermogravimetric measurements have been reported for crystalline cytidine and deoxycytidine. Heats of formation have been determined for a-D-glucose esters and compared with semiempirical quantum mechanical calculations. ... 

Sugar alcohols mannitol and xylitol are used as sweeteners [113]. Mannitol also has some medical uses [114]. Mannitol is produced in a single step from D-fructose by mannitol dehydrogenase. In one E. coli system, reducing power from formate was used and D-fructose was converted to mannitol with 84% molar yield and final titer about 66 g 1 [115]. 

The nature of ester formation between borate and D-mannitol, D-glucitol, D-fructose and D- lucose in aqueous solution at pg 6 - 12 has been elucidated using B- and C-n.m.r. spectroscopy. In order to better understand the action of a gluconate-borate eluent for elution of anions from an anion-exchange resin, the structural features of such solutions have been investigated by potentiometric titrations and C-n.m.r. spectroscopy. Reference to borate esters as transport media in a model membrane will be found in Chapter 2. 

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