Background

The use of lignocellulosic biomass rather than fossil fuel is an environmental sustainable alternative for bioetha-nol production. However, fermentation of lignocellulosic hydrolysates by Saccharomyces cerevisiae is not viable since this yeast cannot ferment xylose naturally. Cur-rent, several studies are being developed to introduce a pathway that allows pentose fermentation by S. cerevi-siae [1]. The bacterium Propionibacterium acidipropio-nici, employed in many industrial processes, is able to efficiently ferment xylose using the enzyme xylose iso-merase. Xylose isomerase, codified by the XI gene, converts xylose to xylulose [2]. This study aims to develop a yeast capable of fermenting xylose through the expression of the P. acidipropioniciXI gene in S. cer-evisiae. Furthermore, the effect of the over expression o