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Browsing by Subject "acceptor reaction"

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  • In vitro synthesis and structural analysis of selected acceptor products of Weissella confusa VTT E-90392 dextransucrase 
    Hou, Yaxi (2014)
    Non-digestible oligosaccharides possess important physicochemical and physiological properties. They have gained great attention because of their potential prebiotic properties. The oligosaccharides have wide food industrial applications as dietary fibers, sweeteners, humectants, and possible weight controlling agents. In this thesis, cloned Weissella confusa VTT E-90392 dextransucrase was used to catalyze the synthesis of oligosaccharides (acceptor products) by acceptor reaction, when sucrose was the glucosyl unit donor. Maltose acceptor reaction was selected to analyze the effects of the concentrations of sucrose and maltose, as well as the dosages of dextransucrase on maltose acceptor products. Other acceptor reactions were also evaluated, with primary lactose and cellobiose acceptor products being purified and partially characterized by MS/MS. Concentrations of sucrose and maltose, as well as their interactions were the most important factors regarding isomalto-oligosaccharides production. The production of overall oligosaccharides could be increased by increasing sucrose and maltose concentrations. Lactose, cellobiose, other disaccharides and trisaccharides could be acceptors for W. consufa dextransucrase. In combination with the structures from previous publications, 2-a-Dglucopyranosyl-cellobiose and 2-a-D-glucopyranosyl-lactose were probably the primary products for cellobiose and lactose, although one trisaccharide synthesized by lactose acceptor reaction remains unknown. In order to verify the characterization, NMR spectroscopic analysis is needed for further study. In conclusion, W. consufa dextransucrase is capable of catalyzing oligosaccharides synthesis, and acceptor reactions would be promising methods in producing prebiotic oligosaccharides.
  • Optimizing the production of maltosylisomaltooligosaccharides to improve functional properties of syrup for baking applications 
    Koivistoinen, Mia (2019)
    Oligosaccharides and dextran can both be produced from sucrose during sourdough fermentation when using dextran producing lactic acid bacteria (LAB). Both dextran and oligosaccharides increase the softness and volume of bread. Since they both are produced simultaneously, the exact effects of dextran and oligosaccharides in sourdough cannot be differentiated. The production of oligosaccharides and dextran can, however, be affected by modifying the concentrations and ratio of sucrose and acceptor and changing the used pH and temperature. The aim of this master’s thesis was to improve the functionality of syrups used in baking by optimizing the production of maltosylisomaltooligosaccharides (MIMO) by oligosaccharides and dextran producing LAB Weissella confusa. The used fermentation temperatures were 20℃ and 30℃. Sucrose concentrations in syrups were 0%, 10% and 20%. Native syrup was used as a control sample. The optimized, functionalized syrup with 20% added sucrose was further used in bread production to evaluate its ability to increase volume and decrease hardness of bread. Breads with added optimized and functionalized syrup, syrup with 0% added sucrose and native syrup as well as control wheat bread were baked. The volume of functionalized syrup containing bread was expected to increase and hardness to decrease compared to other breads. The oligosaccharide production in syrups was qualitatively whereas mono- and disaccharides quantitatively evaluated by high performance anion exchange chromatography with pulse amperometric detection (HPAEC-PAD). Dextran content was evaluated after enzymatic degradation using HPAEC-PAD. The technological impact in bread was evaluated by measuring of the specific volume and texture profile analysis (TPA) of breads containing dextran and MIMO. The results were compared to the breads containing syrup with 0% added sucrose, native syrup and control wheat bread. An increased production of MIMO was obtained by increasing sucrose concentration from 10% to 20%. The peaks of short-chain MIMO decreased, and long-chain MIMO increased as sucrose concentration increased. Temperature did not affect MIMO production. Unlike expected, the volume of functionalized syrup containing bread decreased, and the hardness increased compared to control, bread containing syrup with 0% sucrose or bread with native syrup. This could be due to decreased yeast activity due to increased osmotic pressure, which was caused by a low water amount and yet high sugar content. In further studies, the baking conditions of functionalized syrup containing bread should be optimized to increase the activity of yeast and also the use of functionalized syrup fermented with 10% sucrose should be evaluated in baking.

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