Rheological Analysis of Biopolymer Produced by Aureobasidium Pullulans in Different Sources of Nitrogen

Abstract

In this study, the rheological behaviors of media fermented by two Aureobasidium pullulans strains (IOC 3467 and IOC 3011) were evaluated in different nutritional conditions. The media consisted of crystal sugar (sucrose), as the main carbon source, and different nitrogen sources (ammonium sulfate, sodium nitrate, ammonium nitrate, urea or residual brewery yeast -RBY). Viscosity measurements were performed on cell-free supernatants, from 48-hour fermentation assays, at 25 8 C. Shear rates ranged between 0.1000 and 500 s À1 . All samples showed pseudoplastic behavior. Nevertheless, the viscosimetric profile of each one varied according to the nitrogen source, its concentration and the strain used. The maximum viscosity of 0.06 Pa.s. was achieved at 15.6 s À1 for IOC 3011 strain grown on RBY as nitrogen source.