초록
<P><B>Abstract</B></P> <P>The improvement of yields and productivity for second-generation ethanol (2G) production as well as a better understanding of industrial yeasts and processes are required. Nevertheless, a process to produce 2G ethanol efficiently from lignocellulosic C5-sugars has not yet been proposed. <I>Scheffersomyces stipitis</I> presents good fermentation performance, promising to be a potential biocatalyst for converting C5-sugars to ethanol. In order to evaluate yeast performance, experiments were carried out in a retentostatic extractive vacuum system (REV) with total cell retention, controlled substrate feeding (at different xylose concentrations 100–200gL<SUP>−1</SUP>) and simultaneous ethanol production and extraction. During REV at 100gL<SUP>−1</SUP>, it was possible to achieve an efficient ethanol production. The optimum dilution rate was 0.025h<SUP>−1</SUP>. To avoid stress effects to the yeast metabolism, the ethanol was continuously extracted. Low ethanol concentrations were kept inside the fermenter (25–35gL<SUP>‐1</SUP>), resulting in higher yields and productivity when compared with batch, fed-batch and continuous cultures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An innovative process with simultaneous ethanol fermentation and extraction was developed. </LI> <LI> High cell density of <I>Scheffersomyces stipitis</I> was achieved using retentostat extractive process. </LI> <LI> Bioconversion of concentrated xylose feed streams was evaluated. </LI> <LI> Ethanol levels were kept low inside the reactor avoiding inhibition. </LI> <LI> Ethanol removal was an efficient strategy to increase xylose consumption and ethanol productivity. </LI> </UL> </P>