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Applied and Environmental Microbiology, December 1998, p. 4857-4861, Vol. 64, No. 12
Department of Synthetic Chemistry and
Biological Chemistry,
Received 8 June 1998/Accepted 30 September 1998
Since Saccharomyces cerevisiae lacks the cellulase
complexes that hydrolyze cellulosic materials, which are abundant in
the world, two types of hydrolytic enzymes involved in the degradation of cellulosic materials to glucose were genetically co-immobilized on
its cell surface for direct utilization of cellulosic materials, one of
the final goals of our studies. The genes encoding
FI-carboxymethylcellulase (CMCase) and
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Assimilation of Cellooligosaccharides by a Cell
Surface-Engineered Yeast Expressing
-Glucosidase and
Carboxymethylcellulase from Aspergillus
aculeatus
-glucosidase from the fungus
Aspergillus aculeatus were individually fused with the gene
encoding the C-terminal half (320 amino acid residues from the C
terminus) of yeast
-agglutinin and introduced into S. cerevisiae. The delivery of CMCase and
-glucosidase to the
cell surface was carried out by the secretion signal sequence of the
native signal sequence of CMCase and by the secretion signal sequence
of glucoamylase from Rhizopus oryzae for
-glucosidase,
respectively. The genes were expressed by the glyceraldehyde-3-phosphate dehydrogenase promoter from S. cerevisiae. The CMCase and
-glucosidase activities were
detected in the cell pellet fraction, not in the culture supernatant.
The display of CMCase and
-glucosidase proteins on the cell surface
was confirmed by immunofluorescence microscopy. The cells displaying
these cellulases could grow on cellobiose or water-soluble
cellooligosaccharides as the sole carbon source. The degradation and
assimilation of cellooligosaccharides were confirmed by thin-layer
chromatography. This result showed that the cell surface-engineered
yeast with these enzymes can be endowed with the ability to assimilate
cellooligosaccharides. This is the first step in the assimilation of
cellulosic materials by S. cerevisiae expressing
heterologous cellulase genes.
*
Corresponding author. Mailing address: Department of
Synthetic Chemistry and Biological Chemistry, Graduate School of
Engineering, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan. Phone: 81-75-753-5524. Fax: 81-75-753-5534. E-mail:
atsuo{at}sbchem.kyoto-u.ac.jp.
Applied and Environmental Microbiology, December 1998, p. 4857-4861, Vol. 64, No. 12
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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