Control of Molecular Weight of Dextran Produced by Enzymatic Synthesis

Leuconostoc mesenteroides was immobilized by entrapment in calcium alginate for dextransucrase.In the preparation of dextran by dextransucrase,dextranase was added to control the molecular weight of dextran.Molecular weight of dextran was determined by gel permeation chromatography.After 2 h reaction,weight-average relative molecular mass of dextran produced in the solution descended from 8.52×105 to 2.00×105,then the effect slowed down.The weight-average relative molecular mass of dextran diminished with increasing dextranase dosage,and the effect of enzyme dosage on it was nonlinear.The highest yield of 86.8% was attained by adding two enzymes simultaneously.For dextran synthesis,in 100 mL 10% sucrose solution adding 15 U dextransucrase together with 0.19～0.75 U dextranase,the resulting relative molecular mass of dextran was 1.0×105～2.0×104.