Direct and efficient production of ethanol from cellulosic material with a yeast strain displaying cellulolytic enzymes

Appl Environ Microbiol. 2002 Oct;68(10):5136-41. doi: 10.1128/AEM.68.10.5136-5141.2002.

Abstract

For direct and efficient ethanol production from cellulosic materials, we constructed a novel cellulose-degrading yeast strain by genetically codisplaying two cellulolytic enzymes on the cell surface of Saccharomyces cerevisiae. By using a cell surface engineering system based on alpha-agglutinin, endoglucanase II (EGII) from the filamentous fungus Trichoderma reesei QM9414 was displayed on the cell surface as a fusion protein containing an RGSHis6 (Arg-Gly-Ser-His(6)) peptide tag in the N-terminal region. EGII activity was detected in the cell pellet fraction but not in the culture supernatant. Localization of the RGSHis6-EGII-alpha-agglutinin fusion protein on the cell surface was confirmed by immunofluorescence microscopy. The yeast strain displaying EGII showed significantly elevated hydrolytic activity toward barley beta-glucan, a linear polysaccharide composed of an average of 1,200 glucose residues. In a further step, EGII and beta-glucosidase 1 from Aspergillus aculeatus No. F-50 were codisplayed on the cell surface. The resulting yeast cells could grow in synthetic medium containing beta-glucan as the sole carbon source and could directly ferment 45 g of beta-glucan per liter to produce 16.5 g of ethanol per liter within about 50 h. The yield in terms of grams of ethanol produced per gram of carbohydrate utilized was 0.48 g/g, which corresponds to 93.3% of the theoretical yield. This result indicates that efficient simultaneous saccharification and fermentation of cellulose to ethanol are carried out by a recombinant yeast cells displaying cellulolytic enzymes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cellulase / metabolism
  • Cellulose / chemistry
  • Cellulose / metabolism*
  • Chromatography, High Pressure Liquid
  • Culture Media
  • Enzymes, Immobilized
  • Ethanol / metabolism*
  • Fermentation
  • Genes, Synthetic
  • Genetic Engineering
  • Genetic Vectors
  • Microscopy, Fluorescence
  • Peptide Fragments / genetics
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*

Substances

  • Culture Media
  • Enzymes, Immobilized
  • Peptide Fragments
  • Recombinant Fusion Proteins
  • Ethanol
  • Cellulose
  • Cellulase