By combining modern fiber optics and opto-electronic instrumentation with chemical and biochemical reagent system, it is possible to produce optical biosensors also known as optodes.In the literature there are many papers describing selective and sensitive methods for sensing bioanalytes using such devices.The rapid development of this method indicates is importance in analytical chemistry.The present state of art of optodes is briefly reviwed.The reresentative optical biosensors are described.
The review is focused on recent advances in the enzymatic synthesis of oligosaccharides by exoglycosidases. Reversed hydrolysis, transglycosylation and glycosidase-mediated coupling have been discussed. Relations between catalytic properties of the enzyme used, acceptor molecular structure and their effect on the synthesis results have been highlighted. The work contains 55 references the majority of which appeared after 1996.
An approach for enzymatic sythesis of oligosachcharides via transglycosylation with endo-beta-1,3-glucanase from Oerskovia xanthineolytica is described.Linear -beta-1,3-glucan (laminarin) was used as a donor of glycosyl residues, whereas nitrophenyl glycosides of different monosaccharides served as acceptors.The synthesis was performed in water-organic solvent environment with several combinations of donor/acceptor.Employing p-nitrophenyl-beta-D-xylopyranoside as an acceptor in the presence of 30% acetonitrile resulted in the production of six new glycosides shown by FAB MS to be di-, tri- and tetrasaccharides.This enzyme is therefore suitable for the synthesis of short-chain oligosaccharides.
The review is focused on recent advances in the enzymatic synthesis of oligosaccharides catalysed by endo-glycosidases. Four types of applicable donors (oligo- and polysaccharides, oligosyl fluorides, distorted substrates, glycopeptides) have been presented. Additionally enzymatic glycosylation of glycals by endo-acting glycosidses has been discussed.
Information on beneficial impact of probiotic microorganisms on human health and effects of prebiotic oligosaccharides on proliferation of the latter microflora are presented in the first part of the article. Its further part focuses on fructans, i.e. structures of natural polyfructans and fructooligosaccharides, mechanisms of function of enzymes involved in their synthesis and methods of manufacturing of prebiotic fructooligosaccharides (FOS) in commercial scale.
A mathematical model describing sucrose esters synthesis in biphasic di-n-phentyl ether - water system by lipase from Mucor circinelloides has been elaborated. This model considers correlation between physicochemical factors, dependent on the solvent, substrates, products and temperature, catalytic factors corresponding to the relationship between lipase and the physicochemical factors of the model (Ko=F(A)), as well quantitative factors whose values may be regulated during the reaction (substrate concentration, phase volume coefficient (A) and water concentration). This model was confirmed by syntheses of caprylic and oleic sucrose esters. The maximum reaction yield for the synthesis of caprylic sucrose ester calculated on the basis of the elaborated model was 67,5% and experimental value was 67,8% for A = 44. For oleic sucrose ester, the theoretical and experimental yields of synthesis, were 71,9% and 70,5% respectively. Using this model it is possible to estimate the maximum achievable (in particular conditions) yield of the ester synthesis. It can also be applied for simulations enabling evaluation of the effect of the particular factors on the yield of ester synthesis and resulting optimisation of selected factors in the reaction system. The simulations were performed for two factors of the model in three dimensional space. It was found that the ester synthesis was mostly affected by the following invariable factors: partition coefficients of products (PE, PW) and phase volume coefficient (A). The concentration of water in the water phase and the partition coefficients of sugar (PAL) influenced the yield to a smaller extent.
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