Dra. Patrícia Diaz de Oliveira is an adjunct Professor at Biotechnology College and in Postgraduate Programs of Biotechnology and Food Science and Technology at Federal University of Pelotas, in Pelotas, Rio Grande do Sul, Brazil. She holds a degree in Chemical Engineering from the Federal University of Rio Grande (FURG) and a doctorate in Biotechnology from Federal University of Pelotas (UFPel), doing its research activities at the Biopolymers Laboratory of UFPel. Works specifically with the xanthan pruni hydrocolloid, synthesized by genuinely Brazilian strains of Xanthomonas arboricola pv pruni, and with which performs studies about production, characterization, and application since 2000. Also researches production, characterization, and biodegradation of the bioplastic polyhydroxy butyrate [P(3HB)],synthesizing by Brazilian isolates.


The aim of this work was to evaluate the utilization of analysis of the distribution of relaxation time (DRT) using a dynamic light back-scattering technique as alternative method for the determination of the concentration regimes in aqueous solutions of biopolymers (xanthan, clairana and tara gums) by an analysis of the overlap (c*) and aggregation (c**) concentrations. The diffusion coefficients were obtained over a range of concentrations for each biopolymer using two methods. The first method analysed the behaviour of the diffusion coefficient as a function of the concentration of the gum solution. This method is based on the analysis of the diffusion coefficient versus the concentration curve. Using the slope of the curves, it was possible to determine the c* and c** for xanthan and tara gum. However, it was not possible to determine the concentration regimes for clairana using this method. The second method was based on an analysis of the DRTs, which showed different numbers of relaxation modes. It was observed that the concentrations at which the number of modes changed corresponded to the c* and c**. Thus, the DRT technique provided an alternative method for the determination of the critical concentrations of biopolymers.