초록
<P><B>Background</B></P><P>Consolidated bioprocessing (CBP), integrating cellulase production, cellulose saccharification, and fermentation into one step has been widely considered as the ultimate low-cost configuration for producing second-generation fuel ethanol. However, the requirement of a microbial strain able to hydrolyze cellulosic biomass and convert the resulting sugars into high-titer ethanol limits CBP application.</P><P><B>Results</B></P><P>In this work, cellulolytic yeasts were developed by engineering <I>Saccharomyces cerevisiae</I> with a heterologous cellodextrin utilization pathway and bifunctional minicellulosomes. The cell-displayed minicellulosome was two-scaffoldin derived, and contained an endoglucanase and an exoglucanase, while the intracellular cellodextrin pathway consisted of a cellodextrin transporter and a β-glucosidase, which mimicked the unique cellulose-utilization system in <I>Clostridium thermocellum</I> and allowed <I>S. cerevisiae</I> to degrade and use cellulose without glucose inhibition/repression on cellulases and mixed-sugar uptake. Consequently, only a small inoculation of the non-induced yeast cells was required to efficiently co-convert both cellulose and galactose to ethanol in a single-step co-fermentation process, achieving a high specific productivity of ~62.61 mg cellulosic ethanol/g cell·h from carboxymethyl cellulose and ~56.37 mg cellulosic ethanol/g cell·h from phosphoric acid-swollen cellulose.</P><P><B>Conclusions</B></P><P>Our work provides a versatile engineering strategy for co-conversion of cellulose-mixed sugars to ethanol by <I>S. cerevisiae</I>, and the achievements in this work may further promote cellulosic biofuel production.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s13068-016-0554-6) contains supplementary material, which is available to authorized users.</P>