Synergistic saccharification, and direct fermentation to ethanol, of amorphous cellulose by use of an engineered yeast strain codisplaying three types of cellulolytic enzyme

Appl Environ Microbiol. 2004 Feb;70(2):1207-12. doi: 10.1128/AEM.70.2.1207-1212.2004.

Abstract

A whole-cell biocatalyst with the ability to induce synergistic and sequential cellulose-degradation reaction was constructed through codisplay of three types of cellulolytic enzyme on the cell surface of the yeast Saccharomyces cerevisiae. When a cell surface display system based on alpha-agglutinin was used, Trichoderma reesei endoglucanase II and cellobiohydrolase II and Aspergillus aculeatus beta-glucosidase 1 were simultaneously codisplayed as individual fusion proteins with the C-terminal-half region of alpha-agglutinin. Codisplay of the three enzymes on the cell surface was confirmed by observation of immunofluorescence-labeled cells with a fluorescence microscope. A yeast strain codisplaying endoglucanase II and cellobiohydrolase II showed significantly higher hydrolytic activity with amorphous cellulose (phosphoric acid-swollen cellulose) than one displaying only endoglucanase II, and its main product was cellobiose; codisplay of beta-glucosidase 1, endoglucanase II, and cellobiohydrolase II enabled the yeast strain to directly produce ethanol from the amorphous cellulose (which a yeast strain codisplaying beta-glucosidase 1 and endoglucanase II could not), with a yield of approximately 3 g per liter from 10 g per liter within 40 h. The yield (in grams of ethanol produced per gram of carbohydrate consumed) was 0.45 g/g, which corresponds to 88.5% of the theoretical yield. This indicates that simultaneous and synergistic saccharification and fermentation of amorphous cellulose to ethanol can be efficiently accomplished using a yeast strain codisplaying the three cellulolytic enzymes.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cellulase / genetics
  • Cellulase / metabolism*
  • Cellulose / metabolism*
  • Cellulose 1,4-beta-Cellobiosidase / genetics
  • Cellulose 1,4-beta-Cellobiosidase / metabolism*
  • Culture Media
  • Ethanol / metabolism*
  • Fermentation
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Trichoderma / enzymology
  • Trichoderma / genetics*
  • beta-Glucosidase / genetics
  • beta-Glucosidase / metabolism*

Substances

  • Culture Media
  • Recombinant Proteins
  • Ethanol
  • Cellulose
  • endoglucanase 2
  • beta-Glucosidase
  • Cellulase
  • Cellulose 1,4-beta-Cellobiosidase