Synthesis And Fermentation Kinetics Of Dextran By Leuconostoc Mesenteroides

Dextran is a kind of polysaccharide composed of glucose. It is used widely inthe field of medicine,food and petroleum etc. In industry, Dextran is obtainedfrom the fermentation of sucrose by Leuconostoc mesenteroides.In this work,the culture conditions of Leuconostoc mesenteroides 20074, 21724and 21725 were investigated.It was shown that the growth level of Leueonostocmesenieroides 21724 and 21725 is similar but higher than that of 20074 when inthe same culture medium. The optimal growth conditions for Leueonostocmesenieroides 21724 is: sucrose 130g/L,pH 7.2, temperature 25℃,and vibrationspeed 150r/min. Leuconostoc mesenteroides 21725 is cultured under the samecondition but pH 7.0.Based on our experiments, of these three Leuconostoc mesenteroides, No. 21725afforded the highest conversion from sucrose to dextran, which was obtained in88% yield with a culture medium containing 15% of sucrose after fermentation for18 h at 25℃(in the presence of 10% of Leuconostoc mesenteroides 21725).In this thesis, the fermentation kinetics is discussed. Kinetic equations forLeuconostoc mesenteroides 21725 are as follows: (1) Microorganism growthequation Product formation equation d = 0.39 d + 0.22XSubstrate consumption equation X...