Fructose concentrations

The calibration curves for fructose were compared between PP/FDH/Pt and PP/FCN/FDH/Pt electrodes (prepared by the two-step method) [Fig.23]. In both cases, the response current was directly proportional to fructose concentration up to 10 mM and with a detection range of up to 30mM fructose. The minimum detection limit was 10 //M and 5 mM in the case of PP/FDH/Pt and PP/FCN/FDH/Pt electrodes, respectively. The slope of the linearity was about 80 nA/mM and 450 nA/mM, respectively. 

Figure 1 were not known with sufficient certainty to pinpoint a value. Further investigations, using an accurate evaluation of the final equilibrium fructose concentration, are in progress to determine this dependence. 

Fig. 3 Changes in metabolic fluxes in the energy metabolism of Piromyces induced by changes in the fructose concentration in the medium. The thickness of the arrows is proportional to the calculated fluxes in the presence of 0.1% fructose (Panel A) or 0.5% fructose (Panel B). Abbreviations are as in Fig. 3. (Calculated from the data in Boxma et al. 2004)...

Mammalian sperm cells metabolize D-fructose preferentially as a source of energy. Fructose is formed in cells of the seminal vesicle from D-glucose via reduction to the sugar alcohol sorbitol using NADPH, followed by oxidation of sorbitol to fructose using NAD+. The fructose concentration... 

Fructose concentration in medium Sucrose concentration in medium... 

Dorrell, D.G. and Chubey, B.B., Irrigation, fertilizer, harvest dates and storage effects on the reducing sugar and fructose concentrations of Jerusalem artichoke tubers, Can. J. Plant Sci., 57, 591-596, 1977. 

In the presence of weak acceptors, such as glucose or fructose, initial overall reaction rates decrease significantly with increasing acceptor concentration, whereas they increase with the substrate concentration. Initial rates of acceptor product formation increase with both substrate and acceptor concentration, the dextran formation being suppressed to a major extent only at very high acceptor concentration (at about 3 M glucose or fructose concentration) [20, 21], The acceptor product of fructose, leucrose, does not act as an acceptor, so that high yields (up to about 70%) can be obtained, which is of interest for industrial application. Leucrose has been developed up to the pilot scale (500 kg leucrose produced) for application as an alternative sweetener [24, 25]. 

The above methods are so designed that the oxidation of ketoses by sodium hypoiodite is restricted to a minimum. Bailey and Hopkins studied the conditions under which ketoses would be oxidized. The reaction rate increased with the temperature, and the extent of the reaction, which was studied over the temperature range of 1 to 35 , went through a minimum at 15°. An excess of alkali in the 17-37 range apparently caused enolization of the D-fructose and increased the extent of the oxidation. When the alkali was added progressively in small amounts, this effect was increased 4-5 times and was independent of the D-fructose concentration. Oxalic acid was isolated and the presence of D-erythronic acid was assumed. 

The absorption of sugars and amino acids appears to follow the same basic mechanisms as previously described for the proximal tubule of the kidney (73-77). An additional D-fructose-facilitated carrier mechanism has been located in the brush border membrane that is stereoselective and specific (78). It is Na+-independent and does not accept D- or L-glucose. After transport into the cell, the intracellular fructose concentration is decreased... 

FIGURE 1 Yeast cell growth, viability, sugar consumption, and ethanol production patterns of a typical fermentation. In a synthetic grape juice medium. Triple M (Spiropoulos et al., 2000) was used and inoculated with a commercial strain of 5. cerevisiae. Glucose and fructose concentrations were determined by enzymatic assay, viable cell counts by plating on YPD medium, and cell mass by absorbance at 580 nm. 

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