Sunday, May 4, 2008
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The influence of rice bran extract as nutrient on xylitol production

Ernesto A. Martinez1, Juliana A. F. Santos2, Walter Carvalho2, João B. Almeida e Silva2, and Arnaldo M. R. Prata2. (1) Chemical Division, Institute of Technological Research, São Paulo, Brazil, (2) Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, Estrada Municipal do Campinho, s/n, Lorena, 12602810, Brazil

The bioconversion of xylose into xylitol using rice bran concentration of 5 and 20 g/L was carried out to verify the influence of this supplement on Candida guilliermondii metabolism for xylitol production. Experiments were performed with synthetic medium and sugarcane bagasse hemicellulosic hydrolysate treated with ion-exchange resins and by combining alteration of pH and adsorption with activated charcoal in 125 mL Erlenmeyer flasks, at 30 oC, 200 rpm during 72 h. A batch cultivation of hydrolysate treated with active charcoal was carried out in a 1 L fermentor at 30 oC, pH 5.00, 300 rpm, using oxygen transfer coefficient of 22.86 h-1. The results showed that higher values of xylitol productivity (0.70, 0.71 and 0.62 g/g.L) and yield factor of xylitol (0.71, 0.69 and 0.63 g/g), in synthetic medium, hydrolysate treated with resins and treated with active charcoal, respectively were obtained with 5 g/L of rice bran. The use of lower quantity of rice bran eliminates the stage of fermented broth treatment in the process of xylitol production.

 Acknowledgements
The authors acknowledge the financial support of Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Brazil.