Monday, April 30, 2007

Processing parameters matching effects upon Rhizobium tropici biopolymers reological properties

Flávia Duta Pimenta, Textile Industrial Engineering, Centro de Tecnologia da Industria Quimica e Têxtil, Doutor Manoel Cotrim, 195, Rio de Janeiro, Brazil, Francisca Pessôa De França, Biochemistry Engineering, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Cidade Universitária, Rio de Janeiro, Brazil, and Lea Maria de Almeida Lopes, Instituto de Macromoléculas Professora Eloisa Mano, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Cidade Universitária, Rio de Janeiro, Brazil.

The combined effects of the processing parameters for exopolysaccharides production by Rhizobium tropici was studied as a function of carbon source variation, Ca+2 ions and yeast extract concentration added to the medium. The experiments were carried out using a fermenter with 20L capacity, as the reactor. All processing parameters were online monitored. The temperature [(30±1) °C] and pH value (7.0) were kept constant throughout the experimental time. As statistical tools, a complete 23 factorial planning with central point and response surface were used to investigate the interactions among relevant variables of the fermentation process: mannitol concentration, calcium carbonate concentration, yeast extract concentration, aeration and agitation. The processing parameters setup for reaching a maximum response for reological propriety production was obtained when applying mannitol concentration of 10.0 g/L, calcium carbonate concentration 1.0g/L, yeast extract concentration 1.0 g/L, aeration 1.3 vvm and agitation 800 rpm. Purified biopolymers were analysed by infrared spectrometric analysis, which showed the presence of O-acetyl group. The produced biopolymers in the different experimental condition showed on its composition glucose, galactose, mannose and xylose. Viscosimetric investigation of polysaccharides solutions exposed theirs pseudoplastic behaviour and polyelectrolytic character.