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Poster Presentation 3-39
Xylitol Production from Sugarcane Bagasse Hydrolysate by Ca-Alginate Entrapped Cells in a Stirred Tank Reactor
Walter Carvalho, Silvio S. Silva, Julio C. Santos and Ismael M. Mancilha
Department of Biotechnology, Faculty of Chemical Engineering of Lorena/FAENQUIL Rodovia Itajubá-Lorena km 74.5, Lorena S.P. Brazil 12600-000
Telephone: 0055-12-553-3209; Fax: 0055-12-553-3133; E-mail: silvio@debiq.faenquil.br
Xylitol, a sugar-alcohol with high sweetening power, is used in dietetic foods, sugarless chewing gums and bakery products. This sweetener can be obtained by biotechnological means, although the small productivities are still a bottleneck for the establishment of a large-scale process. Immobilized cell systems have been considered as an alternative to increase the productivities of fermentation processes in spite of the high cell concentrations attained in the reactor. However, the use of these systems on xylitol production has received minimal study to date. In this study, Candida guilliermondii cells were immobilized by entrapment in Ca-alginate beads (2.70 mm in diameter) and used for xylitol production from concentrated sugarcane bagasse hemicellulosic hydrolysate in a stirred tank reactor at 30 ºC. After 60 h of fermentation, 23.5 g/L of xylitol were produced with a yield of 0.58 g xylitol/g xylose consumed and a productivity of 0.39 g/L/h. Despite the high agitation speed employed (500 rpm), a small reduction of 3.7 % (p<0.05) in the mean diameter of the beads was observed at the end of the fermentation run. The adaptation of a basket to prevent the contact between the beads and the turbines allowed the maintenance of the integrity of the beads. However, the xylitol yields and productivities obtained were significantly reduced.
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