17-40: Evaluation of Pichia stipitis acclimatization strategies on rice straw hemicellulosic hydrolysate aiming to ethanol production

Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Ines Roberto, Livia Carneiro and Joo Paulo Silva, Biotechnology, Engineering College of Lorena, University of So Paulo, Lorena, Brazil
In this work, different strategies aiming acclimatization of Pichia stipitis on rice straw hemicellulosic hydrolyzate were evaluated. The acclimatization strategies (A, B, C, D and E) were based on successive transfer of cell at increasing concentrations (45, 60 and 75%v/v) of hydrolyzate with 112 g/L of xylose. During the strategy A was possible to isolate a strain (A75-2) with superior fermentability as compared to the original strain. The increasing transfer’s number, as well as the use of high cell concentrations (strategies B and C) did not improve the cellular adaptation. On the other hand, employing higher levels of oxygen supply during periods of successive transfers (strategy E), the yeast was able to overcome the inhibitory effects of toxic compounds in the hydrolyzate. In this condition, the values of YP/S (0.33 g/g) and QP (0.35 g/L.h) were maintained during the successive transfers, indicating better tolerance of this yeast to the inhibitors in the hydrolyzate. By using this strategy in bioreactor, it was obtained an increase of 7 and 50% on the values of YP/S and QP, respectively, in relation to the reference fermentation (without successive transfer). Based on the data, it was possible to conclude that acclimatization of P. stipitis on undetoxified hydrolyzate is an effective method to overcome numerous problems concerning the physiological stress and inhibition of microbial metabolism. However, the adaptive response of this yeast is dependent on the transfer’s number, cell concentration and oxygenation level of the medium.

  Supported by FAPESP, CNPq and CAPES (BRAZIL)

See more of: Poster Session 2
See more of: General Submissions