Sunday, May 3, 2009
6-15
Ethanol bioproduction from sugarcane bagasse hemicellulosic hydrolysate
The objective of this study was to evaluate the sugar-to-ethanol bioconversion using Pichia stipitis DSM 3651 and sugarcane bagasse hemicellulosic hydrolysate as fermentation medium. A loopful of cells was transferred to 500-mL Erlenmeyer flasks containing 200 mL of medium consisting of (g/L) 30.0 xylose, 3.0 yeast extract, 3.0 malt extract and 5.0 peptone. The cells were then incubated at 30 ºC and 200 rpm. The fermentations were carried out in 250-mL Erlenmeyers flasks containing 100 mL of medium and 3.0 g/L initial cell concentration, at 30 ºC and 200 rpm for 120 h. The medium was composed by the hydrolysate (not treated or treated with ion-exchange resins adsorption or treated with pH alteration and active charcoal adsorption), supplemented with same nutrients described above. Sugars, acetic acid and ethanol concentrations were determined by HPLC and cell concentrations by spectroscopy. As results, 4.9, 6.1 and 7.5 g/L ethanol concentration, 0.2, 0.3 and 0.3 g/g sugar-to-ethanol bioconversion (YP/S) and 0.04, 0.1 and 0.2 g/Lh volumetric productivity (Qp) were obtained in the fermentations that used medium compounded by hydrolysate not treated, treated with pH alteration and active charcoal or treated with resins, respectively. As conclusion, the fermentation that used hydrolysate treated with ion-exchange resins presented the best results in terms of ethanol concentration and Qp, and also presented a good YP/S. As a whole, the present study points out to the fact that the sugarcane bagasse hemicellulosic hydrolysate is a potential fermentation medium to be used for ethanol production. Acknowledgments: Fapesp and CNPq.
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