Fermentation method for producing pullulan polysaccharide

The invention relates to a fermenting method for producing pullulanuse polysaccharide, which is characterized in that the method comprises following steps: firstly, preparing seed culture medium, secondly, preparing fermenting initial culture medium, thirdly, inoculating liquid seeds into the fermenting initial culture medium, wherein the inoculation amount is 3-8%, the fermentation stirring speed is 200-500rpm, the fermentation temperature is 29 DEG C +- 1 DEG C, the ventilation volume is 0.5-10V/V, and the bed pressure is 0.01-0.02MPa, fourthly, complementarily adding the other carbon source after fermenting for 24 hours, wherein the adding amount is 40-80g/L and the adding liuqid is sucrose solution or glucose solution or starch hydrolysate whose pH value is 40-60, and continuingly fermenting for 60-72 hours after adding the carbon source, fifthly, flocculating, hyper-filtrating, barrier-separating, concentrating and drying the fermenting liquid and obtaining the pullulanuse polysaccharide whose molecular weight is between 20-60 million daltons. The invention has simple technique and significant effects and prominently shortens the fermenting time, the fermenting time is 80-100 hours, the production efficiency is increased greatly, energy is saved, the yield rate of product is greatly improved, and the yield can reach by 50%.