Synthesis Dextran By Biological Mehtod And Characterization

Dextran is an extracellular polysaccharides which are production by microbial with sucrose as substrate.At present,moderate,small and very tiny molecular weight of dextran production were widely used in pharmaceutical,food,cosmetics industries and other fields.Different molecular weight dextran were synthesized through Leuconostoc Mesenteroides and Penicillium Cyclopium in this papper.These data could provide help for dextran industrial development and processing of sucrose.The method of high performance gel permeation chromatography determing dextran molecule and the mothed of high performance liquid chromatography（HPLC）determing fructose,glucose and sucrose in the fermentation liquid have been established.The molecule of dextran which synthesis by Leuconostoc Mesenteroides is large,it’s molecular weight is more than 2000k Da.The method of anhydrous ethanol fractional precipitation are used to separate the dextran in Leuconostoc Mesenteroides fermentation liquid.The dextran production can be separated fully when the alcohol concentrationt up to 65%.It is shown that ethanol fractional precipitation could be applied to determine the production of dextran.The substrate of Leuconostoc Mesenteroides synthesizing dextran consist of sucrose 140.0g/L,peptone 7.7g/L,phosphate mixture 1.5g/L,trophic factor 0.7g/L.Under selected condition,the rate of dextran production achieve 96.03%and the rate of reaction is 2.12g·L^-1·h^-1.The process of degrading dextran with enzyme produced by Penicillium Cyclopium have been researched.The dextran can be degrated which molecular weight change from 2000k Da to 10000Da under the condition of dextran concentration 9.0%,initial p H 6.0,temperature 50℃,ratio of feed solution to enzyme 1:1,shaker speed 150r/min,reaction time 48h.The molecular weight of degrading product can be regulated with the reaction time,its distribution range factor is 2.45 according to the above condtions.The analysis of fourier transform infrared（FTIR）spectrum and nuclear magnetic resonance（NMR）spectroscopy indicate that the both dextran product synthesising by Leuconostoc Mesenteroides and degrading by Penicillium Cyclopium areα-dextran,which mostly is straight-chain structure ofα-1,6glycosidic bond,and a little is branch structure ofα-1,3 glycosidic bond.