The KLa influence on ethanol production by Pichia stipitis

摘要

Nowadays, there is a great interest in the development of technologies forethanol production as an alternative combustible, since it can be used insteadof petrol or to blend with petrol, reducing the country’s dependence on oiland imported fuel. It is known that the ethanol production by fermentationis influenced by several process conditions such as pH, temperature, mediumcomposition, oxygen availability, among others. Determining the most suitablefermentation conditions is of large importance for the establishment of asuccessful technology. In the present work, the influence of oxygen transfervolumetric rate (KLa) on xylose to ethanol bioconversion by the yeast Pichiastipitis NRRL Y-7124 was evaluated using a semi-defined fermentation mediumcontaining 90 g/l xylose. The assays were carried out in a bioreactor at 30°C,under different aeration conditions (0.5, 1.0, and 1.5 vvm) and stirring rates(200, 300 and 400 rpm) which resulted in KLa values of 2.3, 18.7 and 65.8 h-1respectively. According to the results, the bioconversion was dependenton the aeration rate employed, the highest ethanol production (27.1 g/l)being achieved when using a KLa of 2.3 h-1. The increase of this parameterto 18.7 and 65.8 h-1 promoted decreases of 52% and 100% on ethanolproduction, respectively. By using a KLa of 65.8 h-1 the ethanol production wastotally deviated to biomass production. Such results are of interest for thedevelopment of a suitable technology for ethanol production by Pichia stipitis.