A METHOD FOR PREPARATION OF alpha-GLUCAN

A method for preparing α-glucan, comprising the steps of:

• inoculating an activated culture of Leuconostoc mesenteroides in a 5 L fermenter with 10% inoculum, the fermenter comprising a fermentation broth that comprises:
• a carbon source that provides a sucrose concentration of between 10-30% by weight;
• a nitrogen source of 0.2-1.0%;
• and
• an initial pH of between 6.8-7.0 and a temperature of 25° C. to 28° C. stirring the activated culture at a speed of 120 rpm;
• after between 5-30 hours of fermentation, adding dextranase to the fermentation culture in an amount that is 1/10,0000 to 5/10,0000 of a total fermentation culture volume;
• controlling a molecular weight of the α-glucan that is prepared in the fermentation culture to be within 10000D by monitoring the fermentation time and an amount of enzyme added;
• after the reaction is terminated, the fermentation culture is decolorized and filtered through a plate and frame filter system and purified by ion exchange and chromatographic separation, and then concentrated and dried to produce a α-glucan dietary fiber product with target molecular weight 500-5000D.