Open Access Highly Accessed Original article

Efficient direct ethanol production from cellulose by cellulase- and cellodextrin transporter-co-expressing Saccharomyces cerevisiae

Ryosuke Yamada1, Yuki Nakatani2, Chiaki Ogino2 and Akihiko Kondo2*

Author Affiliations

1 Organization of Advanced Science and Technology, Kobe University, 1–1 Rokkodaicho, Nada-ku, Kobe, Hyogo 657-8501, Japan

2 Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo 657-8501, Japan

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AMB Express 2013, 3:34  doi:10.1186/2191-0855-3-34

Published: 24 June 2013

Abstract

Efficient degradation of cellulosic biomass requires the synergistic action of the cellulolytic enzymes endoglucanase, cellobiohydrolase, and β-glucosidase. Although there are many reports describing consolidation of hydrolysis and fermentation steps using recombinant Saccharomyces cerevisiae that express cellulolytic enzymes, the efficiency of cellulose degradation has not been sufficiently improved. Although the yeast S. cerevisiae cannot take up cellooligosaccharide, some fungi can take up and assimilate cellooligosaccharide through a cellodextrin transporter. In this study, a S. cerevisiae strain co-expressing genes for several cell surface display cellulases and the cellodextrin transporter was constructed for the purpose of improving the efficiency of direct ethanol fermentation from phosphoric acid swollen cellulose (PASC). The cellulase/cellodextrin transporter-coexpressing strain produced 1.7-fold more ethanol (4.3 g/L) from PASC during a 72-h fermentation than did a strain expressing cellulase only (2.5 g/L). Direct ethanol production from PASC by the recombinant S. cerevisiae strain was improved by co-expression of cellulase display and cellodextrin transporter genes. These results suggest that cellulase- and cellodextrin transporter-co-expressing S. cerevisiae could be a promising technology for efficient direct ethanol production from cellulose.

Keywords:
Bioethanol; Cellulase; Yeast; Cellodextrin transporter; Cell surface display; Cellulose