Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
Sugarcane bagasse is produced nowadays in Brazil in amounts exceeding 150 million tons per year, and represents an important source of fermentable sugars such as xylose, present in the hemicellulosic hydrolysate, obtained after acid pretreatment. However, the presence of cellular inhibitors from this process is shown as an obstacle to the use of xylose arising from this hydrolysate. Therefore, this study aimed at confirming the need of a previous acclimatization in the hydrolysate to obtain an efficient fermentation process and explore this metabolic phenomenon through repeated subcultures in increasing concentrations of hydrolysate (50%, 60%, 70% 80% and 90% v/v) by P.stipitis LADEBIO01. After 40 successive subcultures, it was possible to reduce the fermentation time from 40h to 30h, leading to an increase in the volumetric productivity of ethanol from 0.71 g/L.h, with cells acclimated in 2 steps, to 0.84 g/L.h, after 40 successive subculture in the hemicellulosic hydrolysate by this yeast strain. For effect of comparison, the original strain of this yeast (CBS5774) was acclimatized and its fermentative performance resuted in an ethanol volumetric productivity of only 0.19 g/Lh, suggesting a probable change in the yeast over the years. In addition, it was possible to define, through statistical analysis, the hierarchy of the negative influence of cell inhibitors and to establish cell growth and fermentation by P.stipitis at concentrations of 18g acetic acid/L, 900 mg furfural/L and 300 mg hydroxymethylfurfural/L.