Resumen

PENA, Maribel; CARRASCO, Cristhian; CRESPO, Carla  y  TERRAZAS S. L., Enrique. Influence of oxygen concentration in ethanol production by Pichia stipitis CBS 5773 through fermentation of D-glucose/D-xylose mixtures and Curupaú hydrolyzed. BIOFARBO [online]. 2009, vol.17, n.1, pp. 9-21. ISSN 1813-5363.

The Curupaú residues from the Bolivian wood industry are a potential substrate for ethanol production of second generation. The main goal from ethanol production from hard wood is the efficient conversion of xylose to ethanol. It is dependent of the microbial activity. The current research studied the capability of Pichia stipitis to convert xylose to ethanol with high yield and relatively high velocity. The effect of the proportion of xylose, the influence of oxygen and the inhibition due to a complex substrate (hydrolysate of Curupaú residues) respect to the growth and products formation of Pichia stipitis were studied. Pichia stipitis was cultivated under aerobic conditions using a mixed substrate with different proportions of glucose and xylose, 10:10, 5:15 y 1:19 (g: g), respectively. It was demostrated that higher proportion of xylose (1g glucose: 19g xylose) favors the increasing of biomass (1g/L respect to the other proportions). The oxygen supply favors the biomass production reaching 8.8g/L. Moreover, under microaerobic conditions the biomass production was 7.6g/L. Under microaerobic conditions the fermentation of a complex substrate yielded 52% on ethanol production. However, the yield of ethanol production was 79% in a defined medium. This remarkable difference on yields demonstrates the inhibition on fermentation when the hydrolysate of Curupaú residue was used. This can be explained due to the production of inhibitors during its physicochemical pretreatment.

Palabras llave : lignocellulosic; pretreatment; etanol; xylose; aerobic; microaerobic; yeast.