Physicochemical and biological characteristics of DEAE-derivatized PS7 biopolymer of Beijerinckia indica

Physicochemical and biological characteristics of the exopolysaccharide, PS7, produced from Beijerinckia indica were investigated. The PS7 weight fractions of G1c and G1cUA were 0.45 and 0.25, respectively, and the molar ratio of Glc:Rha:GalUA was approximately 5:1:1.3. The PS7 was chemically derivatized with diethylaminoethyl chloride-HCl (DEAE-HCl), and the resulting modified PS7 contained both positive and negative charges. The elemental and IR analyses were conducted to confirm the successful incorporation of DEAE groups into PST Large increase in nitrogen fraction was observed from the derivatized PS7 by elemental analysis. The characteristic CH3 and CH, peaks originated from DEAE group were detected in H-1 NMR spectrum of the derivatized PS7 as well. Solubility of native PS7 was improved almost twice from 40 to 75% after DEAE-derivatization, while water holding capacity (WHC) drastically decreased from 10,026 to 245%. Oil binding capacity (OBC) of PS7 also significantly dropped from 1528 to 331 % after the derivatization. The [n] values of native and derivatized PS7 were 27.6 and 0.31 dL/g at 25 degrees C, respectively, which means that the DEAE-derivatization significantly decreased the [n] of PST The bile acid binding capacity of PS7 was indirectly determined by measuring the holding capability of cholic acid inside the dialysis membrane. When PS7 was DEAE-derivatized, there was substantial decrease in the cholic acid retardation index (CRI). Up to 8-9 h of dialysis, the derivatized PS7 hold 8.6% less of cholic acid compared to native one. (C) 2007 Elsevier B.V. All rights reserved.