A novel polysaccharide has been observed in uivo by 13C nuclear magnetic resonance (NMR) spectroscopy of the gram-negative bacterium, Zymomonas mobilis. The polysaccharide, which was not removed from the Zmobilis cell by washing with 0.86 % saline, was extracted by mild acid treatment. The structure was elucidated by a combination of NMR techniques, including proton and proton-carbon two-dimensional methods. The structure was determined to be -a-fructofuranosyl-(2-1)-~-fructofuranosyl-(2-6)-. The polysaccharide is unlike levan, a p-(2-6)-fructose polymer which is produced by many bacteria, including Z.mobilis, when grown on sucrose. The polysaccharide isolated here is produced by cells cultured on glucose, fructose or sucrose.Polyfructosides are generally subdivided into two main classes : levans, in which the main interglycoside linkage is p(2 -6), and inulin, in which the main linkage is p(2 -1) [1]. Both inulin and levans are widely distributed throughout the plant kingdom, where they occur as both linear and branched polymers of comparatively low molecular mass and usually contain a small porportion of glucose in addition to fructose.Microbial polyfructosides are generally of the levan type. Levan is produced by both gram-positive and gram-negative bacteria [2] including Zymomonas mobilis. Z . mobilis is a gramnegative bacterium which can ferment only glucose, fructose and sucrose to ethanol anaerobically via the EntnerDoudoroff pathway. Growth on sucrose results in the synthesis of levan while in the absence of sucrose no levan production occurs. The levan produced by Z . mobilis has been shown to be typical of the bacterial levans containing only fructose in the furanose ring form, linked p(2 -6) with p(2 -1) branch points and a very high molecular mass (approximately 10 MDa) [3].The novel polyfructoside described here has been isolated from Z . mobilis cells grown on glucose and has been found to have a different structure to that of levan and a lower molecular mass.
MATERIALS AND METHODS
Ma terialsSephacryl 200 was obtained from Pharmacia ; the anionexchange resin, AG3-X4A, was obtained from Bio-Rad. D 2 0 ( 2 99.75 % D) was obtained from the Australian Atomic Energy Commission, Lucas Heights. All other reagents were analytical reagent grade.