Affiliation:
1. Carlsberg Laboratory, Yeast Biology, Gamle Carlsberg Vej 10, DK-2500 Valby, Copenhagen, Denmark
2. Department of Microbiology, Friedrich Schiller University, and Junior Research Group: Fungal Pathogens, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute, Beutenbergstrasse 11a, D-07745 Jena, Germany
Abstract
ABSTRACT
Synthesis of chitin de novo from glucose involves a linear pathway in
Saccharomyces cerevisiae
. Several of the pathway genes, including
GNA1
, are essential. Genes for chitin catabolism are absent in
S. cerevisiae
. Therefore,
S. cerevisiae
cannot use chitin as a carbon source. Chitin is the second most abundant polysaccharide after cellulose and consists of
N
-acetylglucosamine (GlcNAc) moieties. Here, we have generated
S. cerevisiae
strains that are able to use GlcNAc as a carbon source by expressing four
Candida albicans
genes (
NAG3
or its
NAG4
paralog,
NAG5
,
NAG2
, and
NAG1
) encoding a GlcNAc permease, a GlcNAc kinase, a GlcNAc-6-phosphate deacetylase, and a glucosamine-6-phosphate deaminase, respectively. Expression of
NAG3
and
NAG5
or
NAG4
and
NAG5
in
S. cerevisiae
resulted in strains in which the otherwise-essential Sc
GNA1
could be deleted. These strains required the presence of GlcNAc in the medium, indicating that uptake of GlcNAc and its phosphorylation were achieved. Expression of all four
NAG
genes produced strains that could use GlcNAc as the sole carbon source for growth. Utilization of a GlcNAc catabolic pathway for bioethanol production using these strains was tested. However, fermentation was slow and yielded only minor amounts of ethanol (approximately 3.0 g/liter), suggesting that fructose-6-phosphate produced from GlcNAc under these conditions is largely consumed to maintain cellular functions and promote growth. Our results present the first step toward tapping a novel, renewable carbon source for biofuel production.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
50 articles.
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