Evidence for microbial polysaccharide preparations containing polyester substituents

CPMAS 13C-n.m.r. spectroscopy was employed to characterize the composition and solid phase morphology of gellan, welan, rhamsan and NW11. Spectra indicated that commercial preparations of these polysaccharides, which share a similar molecular backbone, contain a non-carbohydrate component exhibiting four inequivalent carbon atoms. Isolation of this component, followed by 13C-n.m.r. in CHCl3 and MS analysis, revealed its structure to be poly(beta-hydroxybutyrate). Evidence is presented which suggests that this polyester may be a covalent adduct to the above polysaccharides, although this cannot be unambiguously determined at this time. Further experimentation is in progress.