Studies Of Dextran Preparation By Enzyme Engineering Technology

In this paper, the basic data of updating dextran productional technology was attained by studying fermentation process of Leuconostoc mesenteriodes-0326 and producing dextransucrase condition and the immobilization technology of dextransucrase.Reforming traditional fermentation technology was brought out by making use of enzymatic engineering,resulting in promoting dextran productional technology ,raising product quality and improving production surroundings.It laid the foundation of sequential production ,reusing enzyme and controlling molecular-weight of dextran.Firstly, the process in the preparation of dextran through the fermentation of Leuconostoc mesenteriodes-0226 and Correlative Factors of producing dextransucrase were studied in the paper. The adhesive viscosity, pH value, the production of fructose and dextran, variation of molecular-weight and the fermentation inducer was researched, and the related engineering curve of the dextran fermentation was acquired. Different molecular-weight of dextran might be obtained by directed fermentation on this base. The optimization factors of producing dextransucrase from Lmesenteriodes -0326 were that the culture medium of about 5% sucrose was optimal condition of producing dextransucrase and the product was easy to be isolated, the yield of dextransucrase reached maximum at 35C. dextransucrase activity was raised rapidly through the cooperation o f Mn2+Ca2+ or at pH 8.0.Secondly based on the results of the experiments above, we obtained the technology conditions and method of the immobilization of dextransucrase by sodium alginate.And during the course of continuous reaction some parameters such as in different flowing velocity(rounds per minutes),flowing direction,concentrationof substrate solution(sucrose),temperature,pH value were controlled and investigated. The optimum conditions for dextran production in packed bed reactor were down-flowing direction feeding , 30%sucrose , 60rpm, T28-30'C ,pH4.5--5.5 .But the fluidifying -bed reactor model is better than the packedFinally We took chitosan as to carrier,researching the result that two kinds of appearance of chitosan:powder form and bead form to immobilze the dextransucrase The result indicated that the optimum immobilizing condition is that temperature: 25C,pH:5.0,amount of enzyme: 15ml,densityofglutaraldehyde:1.0%,5h.