Sunday, May 4, 2008
3-60

Biotechnological Production of Xylitol: Optimization of Monosaccharide Recovery by Post-Hydrolysis of Hemicellulsic Hydrolysate after Acid hydrolysis of Sugarcane Baggase

Boutros Fouad Sarrouh, Juan Daniel Rivaldi, Ricardo De Freitas Branco, and Silvio Silverio da Silva. Department of Biotechnology, Escola de Engenharia de Lorena, Universidade de São Paulo, Estrada Municipal do Campinho, s/n CEP 12.602-810, Lorena - SP, Brazil

Sugarcane bagasse hemicellulosic hydrolysate was obtained with an initial xylose concentration of 18,4 g/L at the end of its hydrolysis. The acid hydrolysis represented a conversion efficiency (hemicellulose to xylose) of 73 %, considering that the maximum theoretic xylose concentration found in the hemicellulosic hydrolsate is of 25 g/L. In order to increase the xylose concentration found in the obtained hemicellulosic hydrolysate, a post hydrolysis stage was carried out. At the end of the post-hydrolysis stage, almost a complete conversion of xylose-oligosaccharides to xylose-monosaccharides took place, resulting in a 20% increase in the total xylose concentration, from 18,4 g/l in the hemicellulosic hydrolysate to 23,5 g/l in the post-hydrolysate. The post-hydrolysis stage consisted in heating the obtained hemicellulosic hydrolysate at 121oC for 10min. Such heating will prevent the re-polymerization of the produced monosaccharides and at the same time will degrade the formed oligosaccharides, thus leading to an optimum xylose extraction from the hemicellulosic fraction of sugarcane bagasse. fermentation process for xylitol production using post-hydrolysate showed better xylose-xylitol conversion efficiency of 76% (0,7 g xylitol/g xylose) and volumetric productivity of 0,68 g xylitol/l.h than the original hemicellulosic hydrolyste, which resulted in a conversion efficiency of 71% (0,65 g xylitol/g xylose) and volumetric productivity of 0.61 g xylitol/l.h. Such results were expected since the inhibitors concentrations were higher for the original hydrolsyate than that for post-hydrolsyate, thus more toxic substances were found in the original hydrolystae that influenced negatively in the fermentation process yield and productivity. Acknowledgment: FAPESP, CNPq

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