Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2016 Apr 15:6:24550.
doi: 10.1038/srep24550.

Engineering of a novel cellulose-adherent cellulolytic Saccharomyces cerevisiae for cellulosic biofuel production

Zhuo Liu  1 , Shih-Hsin Ho  2   3 , Kengo Sasaki  2 , Riaan den Haan  4 , Kentaro Inokuma  2 , Chiaki Ogino  1 , Willem H van Zyl  5 , Tomohisa Hasunuma  2 , Akihiko Kondo  1   6
Affiliations

Engineering of a novel cellulose-adherent cellulolytic Saccharomyces cerevisiae for cellulosic biofuel production

Zhuo Liu et al. Sci Rep. .

Abstract

Cellulosic biofuel is the subject of increasing attention. The main obstacle toward its economic feasibility is the recalcitrance of lignocellulose requiring large amount of enzyme to break. Several engineered yeast strains have been developed with cellulolytic activities to reduce the need for enzyme addition, but exhibiting limited effect. Here, we report the successful engineering of a cellulose-adherent Saccharomyces cerevisiae displaying four different synergistic cellulases on the cell surface. The cellulase-displaying yeast strain exhibited clear cell-to-cellulose adhesion and a "tearing" cellulose degradation pattern; the adhesion ability correlated with enhanced surface area and roughness of the target cellulose fibers, resulting in higher hydrolysis efficiency. The engineered yeast directly produced ethanol from rice straw despite a more than 40% decrease in the required enzyme dosage for high-density fermentation. Thus, improved cell-to-cellulose interactions provided a novel strategy for increasing cellulose hydrolysis, suggesting a mechanism for promoting the feasibility of cellulosic biofuel production.

PubMed Disclaimer

Figures

Figure 1
Figure 1. Engineering cellulolytic S. cerevisiae for cellulosic ethanol production via either cell-surface display or secretion of enzymes.
PSED1, SED1 promoter; SS, secretion signal; ASED1, SED1 anchoring region; TSAG1, SAG1 terminator.
Figure 2
Figure 2. Time course of direct ethanol production from cellulosic materials.
Ethanol was produced from 20 g/L PASC (a) and from 10 g/L Avicel (b). Data are presented as the means and standard deviations of triplicate measurements.
Figure 3
Figure 3. Time course of direct ethanol production using recombinant strains EG-D-CBH1-D-CBH2-D and EG-S-CBH1-S-CBH2-S.
Ethanol was produced from 20 g/L PASC (a) and from 10 g/L Avicel (b). Data are presented as the means and standard deviations of triplicate measurements.
Figure 4
Figure 4. SEM micrographs of the interactions between cellulolytic S. cerevisiae cells and cellulosic materials.
Interactions with PASC (a,b) and with Avicel (c,d). Cellulolytic cells (30 g/L) were incubated with 1% cellulosic materials (PASC or Avicel) for 2 h, and the cellulosic materials were used for SEM imaging. Scale bars are 10 μm.
Figure 5
Figure 5. SEM micrographs of the interactions between PASC and EG-D-CBH1-D-CBH2-D cells.
The observation conditions were the same as those used in Fig. 4. Scale bars are 1 μm.
Figure 6
Figure 6. Comparison of cellulosic feedstock rice straw with MC6 for cellulosic ethanol production.
(a) SEM micrographs of the surface structures on cellulosic materials (I,II); observation of adhesion between strain EG-D-CBH1-D-CBH2 and cellulosic materials using optical microscopy (I’,II’). (b) Ethanol yields at 96 h of fermentation from 25 g/L rice straw and MC6, respectively. Data are presented as the means and standard deviations of triplicate measurements.
Figure 7
Figure 7. Evaluations of commercial cellulase addition in ethanol production from 100 g/L MC6.
(a) Ethanol production at 96 h of fermentation with the addition of 0, 0.2, 0.6, 1.0, 1.4, 1.8, and 2.2 FPU/g-biomass cellulase (C-Tec2). (b) Cellulolytic activities in the fermentation media at 0 and 96 h of fermentation with the respective strains. Data are presented as the means and standard deviations of triplicate measurements.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Sheehan J. Engineering direct conversion of CO2 to biofuel. Nat. Biotechnol. 27, 1128–1129 (2009). - PubMed
    1. Lynd L. R., Wyman C. E. & Gerngross T. U. Biocommodity Engineering. Biotechnol. Prog. 15, 777–793 (1999). - PubMed
    1. Himmel M. E. et al. Biomass recalcitrance: engineering plants and enzymes for biofuels production. Science 315, 804–807 (2007). - PubMed
    1. Schubert C. Can biofuels finally take center stage? Nat. Biotechnol. 24, 777–784 (2006). - PubMed
    1. van Zyl W. H., Lynd L. R., den Haan R. & McBride J. E. Consolidated bioprocessing for bioethanol production using Saccharomyces cerevisiae. Adv. Biochem. Eng. Biotechnol. 108, 205–235 (2007). - PubMed

Publication types