Tuesday, April 20, 2010
11-26

Influence of medium nutritional composition and oxygen transfer rate on xylose-to-ethanol conversion by Pichia stipitis

João Paulo A. Silva1, Solange I. Mussatto2, Livia M. Carneiro1, José A. Teixeira2, and Inês C. Roberto1. (1) Department of Biotechnology, Engineering College of Lorena, University of São Paulo, Estrada Municipal do Campinho, s/n, Lorena, 12.602-810, Brazil, (2) IBB - Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar, Braga, Portugal

Two important aspects to be considered on ethanol production from xylose include the nutritional composition of fermentation medium and the oxygen transfer volumetric rate (KLa). Among these, oxygen plays an important role in pentoses fermentation since it determines the partitioning of the flux of carbon from substrate between growth and product formation. The present work evaluated the influence of medium nutritional composition and different KLa values on ethanol production by Pichia stipitis in a bioreactor, under high xylose concentration (90.0 g/L). In a first step, the effect of urea, MgSO4x7H2O and yeast extract addition to the medium were evaluated. Addition of urea (2.3 g/L) and yeast extract (3.0 g/L) were important to improve the process parameters, but the yeast extract was the most important nutrient source since ethanol production was not observed in its absence. In the following step, different KLa values (0.7, 2.3, 3.3, 4.9, 11.7 and 12.1 h-1) were evaluated during the ethanol production in a 1.6-L bioreactor. The highest ethanol production (about 27 g/L in 84 h) was achieved when a KLa value of 4.9 h-1 was employed. The KLa increase proportioned the yeast metabolism deviation from ethanol production to cell growth, while its decrease resulted in a lower consumption of substrate, ensuring a lower yield of ethanol. Oxygen availability and nutritional composition of fermentation medium proved to be variables of great influence on xylose-to-ethanol conversion by Pichia stipitis. Establishing suitable conditions is of great importance to achieve elevated ethanol conversion results. Acknowledgements: Santander (Brazil).

See more of Poster Session Two
See more of General Submissions

See more of The 32nd Symposium on Biotechnology for Fuels and Chemicals (April 19-22, 2010)