A comparative study on the physico-chemical properties of bacterial capsular polysaccharides from different serotypes of Klebsiella

Comparative studies on various physico-chemical properties of bacterial capsular polysaccharides from different serotypes of Klebsiella have been investigated. A correlation of the primary structures with the solution properties of different polymers has been established based on spectrophotometric, spectrofluorometric and viscometric measurements. Absorption studies on four experimental biopolymers (K7, K14, K17 and K26) with four cationic dyes, pinacyanol choloride (PCYN), acridine orange (AO), toluidine blue (TB) and phenosafranin (PSF) indicated that chromotropic capability of the polymers with respect to induction of metachromasy followed the order: K7 > K14 > K26 > K17. Formation of (1:1) stoichiometric polymer–dye complexes suggested stacking conformation in all the four polymers. Fluorescence quenching of AO and PSF dye induced by the polymers also revealed the quenching efficiency of polymers to follow the same order as revealed in the absorption studies. The Stern–Volmer constant (KSV) also supported similar trend. The order of chromotropic character and fluorescence quenching of the polymer were in conformity with their charge densities. Viscosity measurements of all the four capsular polysaccharide solutions showed the characteristic behavior of polyelectrolytes indicating sharp increase in reduced viscosity of the aqueous polysaccharide solution at lower dilution. Molecular weight of the bacterial polysaccharides were also determined from viscometric measurements.