How Is Pullulan Made?

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Pullulan is a kind of polysaccharide with a linear chain staircase-like structure made by fermentation of the fungus Aureobasidium pullulans., usually called black yeast. The whole production process mainly includes material preparation, strain culture, fermentation, filtration, decolorization, concentration, drying, and packing. Pullulan is produced inside the fungal cell and excluded from the body, forming a sticky and loose layer outside to prevent water loss and protect itself from predation. It also facilitates the movement of substances in and out of the cell.

Aureobasidium pullulans strain, like black yeast
Aureobasidium pullulans strain, like black yeast

Pullulan has repeating units of three maltotrioses, which are linked internally by α-1,4 glycosidic bond and connected externally by α-1,6 glycosidic bond, with molecular weights of 1.5*104 to 1.0*107 Da. In commercial production, the pullulan average molecular weight is 200KDa.

pullulan staircase-like structure
Pullulan staircase-like structure

Material preparation

The raw materials for the fermentation of pullulan are similar to other microbial fermentations, including nitrogens, carbons, oxygen, and phosphates.

The most commonly used carbon source is glucose and the nitrogen sources are ammonium salts, ammonium sulfate, Ammonium nitrate, urea, peptone, yeast extract, soybean pomace, and corn steep liquor. the choice of nitrogen and carbon sources directly affects the yield and molecular weight of pullulan polysaccharide. Nowadays, people are still trying different nitrogen and carbon sources to achieve the maximum yield.

Strain Culture

The strain culture includes two stages: shake flask culture and seed pot culture. After sterilization by steam at a high temperature, the strain is transferred to the culture medium and then to the shake flask. Seed pot culture is to mix raw material and strain, culture temperature 28-32℃, pot pressure 0.02-0.06MPa, culture cycle about 18-30 hours.

There are many strains that produce pullulan, Tremella mesenterica, Cytaria harioti, Cytaria darwinii, Cryphonectria parasitica, Teloschistes flavicans, and Rhodotorula bacarum. Why is this strain A. Pullulans chosen? It is because of its significant yield. This strain has five forms: yeast-like cells, young blastospores, swollen blastospores, chlamydospores, and mycelia, among which the yeastlike state produces the most polysaccharide.


The fermentation stage of Pullulan is to move the seed tank culture strain and raw material into the fermenter and incubate it for 60-75 hours at a temperature of 28-32°C, tank pressure of 0.02-0.06 MPa, and airflow of 1000-2700 m3/h. People change the condition parameters to try to find the optimal fermentation environment, including whether to stir or not, and change the airflow rate, temperature, and PH level.


In the fermenter, there are strain cells, culture medium, pullulan, etc. By adding flocculants, the particulate matter, strain cells, etc. are combined to form large flocs that are easily filtered and removed later.


Through the first filtration, the large particles, precipitates, etc. are removed and the rest is purified pullulan solution.

filtration in pullulan manufacturing

Color Removal

Melanin and fine impurities are removed from the solution using edible-grade activated carbon, which is also an important part of the product cost.

Secondary Filtration

The second filtration is to remove the activated carbon to obtain a pure pullulan polysaccharide solution.


The concentration of pullulan solution by high-temperature steam, reducing the moisture content


We get the pure pullulan powder by spray drying through the tower device. The evaporation capacity of the drying tower is 2000 kg/h, and the temperature of the inlet air is 170-230°C. Unlike the method with alcohol additives (pullulan is insoluble in alcohol), this method achieves 0 alcohol residue.

spray drying tower in pullulan production
Spray drying tower in pullulan production

Packing and Storage

Pack the finished products according to the customer’s requirements, 10kg, 20kg per carton, drum, bag, etc. Finally stored in the warehouse.

pullulan packed in 25kg drum
Pullulan packed in 25kg drum


The whole manufacturing process of pullulan includes raw material preparation, strain culture, fermentation, filtration, color removal, concentration, drying, packaging, and storage.

Through the above article, I think you should have an understanding of how Pullulan polysaccharide is made, if you have any questions, please feel free to discuss, contact us at

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