Purification and Characterization of a Novel Polysaccharide Involved in the Pellicle Produced by a Thermotolerant AcetobacterStrain

Acetobacterstrains able to produce a thick pellicle at 37°C were screened among many thermotolerant strains isolated from fruits in Thailand. As a result, Acetobactersp. SKU 1100 was selected as the producer of a relatively thick pellicle even when cultured at higher temperatures such as 37°C or 40°C. This strain could produce a pellicle polysaccharide in a shaking submerged culture as well as under static culture conditions. The polysaccharide was found to be attached to the bacterial cells. Although the polysaccharide production was higher at 30°C than at 37°C in shaking submerged culture, the productivity in static culture was not decreased even at higher temperatures. The membrane-attached polysaccharide was purified from the SKU 1100 strain by cell disruptions using either ultrasonic treatment or lysozyme treatment, followed by ultracentrifugation, enzyme treatments, dialysis against SDS, DEAE-cellulose column chromatography, alcohol precipitation, and gel filtration chromatography. The polysaccharide purified by the sonic treatment and also by the mild conditions using lysozyme treatment had the same average molecular mass of 120 kDa. The purified polysaccharide was composed of three different monosaccharides; glucose, galactose, and rhamnose, in an approximately equimolar ratio of 1:1:1.