Co-fermentation of cellobiose and xylose using beta-glucosidase displaying diploid industrial yeast strain OC-2 |
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Authors: | Satoshi Saitoh Tomohisa Hasunuma Tsutomu Tanaka Akihiko Kondo |
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Institution: | (1) Toyota Biotechnology & Afforestation Laboratory, Toyota Motor Co., 1099, Marune, Kurozasa-cho, Miyoshi Aichi, 470-0201, Japan;(2) Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe 657-8501, Japan;(3) Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe 657-8501, Japan |
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Abstract: | The co-utilization of sugars, particularly xylose and glucose, during industrial fermentation is essential for economically
feasible processes with high ethanol productivity. However, the major problem encountered during xylose/glucose co-fermentation
is the lower consumption rate of xylose compared with that of glucose fermentation. Here, we therefore attempted to construct
high xylose assimilation yeast by using industrial yeast strain with high β-glucosidase activity on the cell surface. We first
constructed the triple auxotrophic industrial strain OC2-HUT and introduced four copies of the cell-surface-displaying β-glucosidase
(BGL) gene and two copies of a xylose-assimilating gene into its genome to generate strain OC2-ABGL4Xyl2. It was confirmed
that the introduction of multiple copies of the BGL gene increased the cell-surface BGL activity, which was also correlated
to the observed increase in xylose-assimilating ability. The strain OC2-ABGL4Xyl2 was able to consume xylose during cellobiose/xylose
co-fermentation (0.38 g/h/g-DW) more rapidly than during glucose/xylose co-fermentation (0.18 g/h/g-DW). After 48 h, 5.77%
of the xylose was consumed despite the co-fermentation conditions, and the observed ethanol yield was 0.39 g-ethanol/g-total
sugar. Our results demonstrate that a BGL-displaying and xylose-assimilating industrial yeast strain is capable of efficient
xylose consumption during the co-fermentation with cellobiose. Due to its high performance for fermentation of mixtures of
cellobiose and xylose, OC2-ABGL4Xyl2 does not require the addition of β-glucosidase and is therefore a promising yeast strain
for cost-effective ethanol production from lignocellulosic biomass. |
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