Description
[About Pullulan polysaccharide]
Pullulan, an extracellular water-soluble microbial polysaccharide produced by strains of Aureobasidium pullulans is a linear -D-glucan made mainly of maltotriose repeating units interconnected via -(16)linkages. It is a kind of characteristic polysaccharide ,which was first found by R.Bauer in 1938. The molecular weight of pullulan is from 4.8104 to 2.2106 dol. The average molecular weight of Commodity pullulan is 2105consisting approximately of 480 maltotrioses.
[Application]
A number of potential applications have been reported for pullulan as a result of its good film-forming properties; pullulan can form thin film which is transparent, oil resistant and impermeable to oxygen. Pullulan may be used as a coating and packaging material, as a sizing agent for paper, in plywood manufacturing, and in dielectric condensors, as a starch replacer in low-calorie food formulations, in cosmetic emulsions, and in other industrial and medicinal applications. Other potential applications include use as an adhesive binder, thickener and encapsulating agent. In conclusion, this polysaccharide is of economic importance with increased applications to the food, pharmaceutical and chemical industries.
[Production]
According to the reports, Aureobasidium pullulans is the producer of pullulan, but some difficulties exist in industry production, such as low sugar utilization, melanin produced during fermentation. Commercial production of pullulan only made in Japan, its output is close to ten thousand tons. But according to the reports overseas, the production concentration is low, most is 2050g l-1.Besides, pullulan fermentation needs 96144h, which is too long for industry production. Many research institutes of China reported pullulan concentration of 3060g l-1 had been achieved. Furthermore melanin is produced during fermentation which will make it more difficult to purify the exopolysaccharide at the end of fermentation, besides, long fermentation time(108144h, even 156h) is unfavorable to industry production. A strain of Aureobasidium pullulans was isolated by our lab in 1980s, a mutant was achieved via U.V. and NTG inducing, which could produce a large amount of extracellular polysaccharide, could have high sugar utilization, and didnt produce melanin during the fermentation.? Fermentation conditions of this mutant were studied in a rotary shaking incubator and a 16L fermentor, a maximum pullulan concentration of 70gL-1, pullulan yield of 60% and sugar utilization of 98% were achieved. Further study on the abstraction technology was carried out, which solved a series of industrialization technology difficulties. We got superior pullulan product similar to that of Japanese. From all of the reports about pullulan, our pullulan-producing strain of A. pullulans is better than others, which pullulan concentration is stable, polysaccharide yield is high, no pigment is observed during the fermentation but its fermentation time is half of others. Therefore, the advantage of this strain to industry production is obvious, its industrialization value is larger than others.
