Purification and Chemical Properties of Acinetobacter calcoaceticus A2 Biodispersan

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Abstract
The extracellular dispersant of Acinetobacter calcoaceticus A2, referred to as biodispersan, was concentrated by ammonium sulfate precipitation and deproteinized by hot phenol treatment. The active component was an anionic polysaccharide (PS-A2). The specific activity of PS-A2 was approximately three times greater than that of crude biodispersan. PS-A2 had a sedimentation constant of 1.39 S, a diffusion coefficient of 18.8 × 10−8 cm2 s−1, and a partial molar volume of 0.65 cm3 g−1, yielding an average molecular weight of 51,400. Titration of the polymer gave two inflection points: pK1 = 3.1 (1.15 μEq/mg) and pK2 = 8.0 (0.4 μEq/mg). PS-A2 slowly consumed 1.10 μmol of periodate per mg. The 13C nuclear magnetic resonance spectrum of PS-A2 indicated four methyl groups, four carbonyl C atoms, and four signals in the anomeric region (95 to 110 ppm), indicative of the presence of four different monosaccharides. Strong acid hydrolysis of PS-A2 yielded four reducing sugars: glucosamine, a 6-methyl aminohexose, galactosamine uronic acid, and an unidentified amino sugar. Ruthenium red binding to PS-A2 was stoichiometric: 1 molecule of dye bound per 2.0 carboxyl groups.