ABSTRACT
Pullulan solutions are viscous and pseudoplastic, with the deviation from Newtonian behavior increasing with pullulan concentration. Purified pullulan is highly water soluble, nonhygroscopic, nontoxic, tasteless, odorless, biodegradable, impermeable to oxygen, and resistant to oil and grease and changes in temperature and pH. Pullulan was digested by pullulanase and amyloglucosidase, and the resultant glucose then reacted with glucose dehydrogenase to reduce oxidized nicotinamide adenine dinucleotide, allowing the reaction to be followed spectrophotometrically at 340 nm. Aureobasidium pullulans is a ubiquitous organism. Its tolerance to high concentrations of sugars and neutral salts, a wide pH range, and high doses of ultraviolet radiation ensures that it occurs in a large variety of natural and artificial habitats. Several reports have shown that pullulan and exopolysaccharide yields can be markedly affected by the concentrations of growth factors including vitamins, and cations in the medium. In some cases, these components induced morphological changes which appeared to correlate with the levels of exopolysaccharide formed.
