Intercalation of the Microbial Biopolymers Welan Gum and EPS I into Layered Double Hydroxides

Johann Plank, Serina Ng, Sebastian Foraita
2012 Zeitschrift für Naturforschung. B, A journal of chemical sciences  
Three microbial polysaccharides, namely welan gum, scleroglucan, and EPS I, a novel polysaccharide obtained from a newly isolated bacillus species with structural similarities to xanthan gum, were employed in the fabrication of bio-nanocomposites based on layered double hydroxides (LDH). Synthesis was performed by direct co-precipitation of Zn(NO3)2 and Al(NO3)3 in the polysaccharide solutions at pH ~ 8.5. The reaction products were characterized by powder X-ray diffraction (XRD), elemental and
more » ... XRD), elemental and thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning and transmission electron microscopy (SEM and TEM). It was found that welan gum is successfully intercalated into the Zn-Al-LDH structure, giving a d-spacing of 2:38 nm for the interlayer distance, while neutral scleroglucan failed to be intercalated. Instead, this biopolymer was only surface-adsorbed on inorganic CaAl-OH-LDH platelets, as was evidenced by de-washing experiments. These results indicate that the anionic functionality of the polysaccharides presents a main driving force behind their intercalation. In contrast to regular xanthan gum, EPS I was intercalated into the LDH structure to give a sharp X-ray reflection representing a d-spacing of 2:77 nm. This behavior proves that slight modifications of the polysaccharide can greatly improve its intercalation ability.
doi:10.5560/znb.2012-0081 fatcat:wrj6nip6jvb5bpyclpx2k22jte