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. 2015 Apr 22:5:9593.
doi: 10.1038/srep09593.

Direct ethanol production from starch using a natural isolate, Scheffersomyces shehatae: Toward consolidated bioprocessing

Ayumi Tanimura  1 , Minako Kikukawa  2 , Shino Yamaguchi  1 , Shigenobu Kishino  1 , Jun Ogawa  1 , Jun Shima  3
Affiliations

Direct ethanol production from starch using a natural isolate, Scheffersomyces shehatae: Toward consolidated bioprocessing

Ayumi Tanimura et al. Sci Rep. .

Abstract

Consolidated bioprocessing (CBP), which integrates enzyme production, saccharification and fermentation into a one-step process, is a promising strategy for cost-effective ethanol production from starchy biomass. To gain insights into starch-based ethanol production using CBP, an extensive screening was undertaken to identify naturally occurring yeasts that produce ethanol without the addition of any amylases. Three yeast strains were capable of producing a significant amount of ethanol. Quantitative assays revealed that Scheffersomyces shehatae JCM 18690 was the strain showing the highest ethanol production ability. This strain was able to utilize starch directly, and the ethanol concentration reached 9.21 g/L. We attribute the ethanol-producing ability of this strain to the high levels of glucoamylase activity, fermentation potential and ethanol stress tolerance. This study strongly suggests the possibility of starch-based ethanol production by consolidated bioprocessing using natural yeasts such as S. shehatae JCM 18690.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1. Changes in ethanol (a), starch (b) and glucose (c) concentrations of S. shehatae JCM 18690 (filled circles), ATY945 (open circles), ATY1112 (open triangles) and S. shehatae NBRC 1983 (crosses) from 10% starch liquid medium.
Data are the means ± standard deviations (error bars) of three assays.
Figure 2
Figure 2. Changes in α-amylase (a) and glucoamylase (b) activity of S. shehatae JCM 18690 (filled circles), ATY945 (open circles), ATY1112 (open triangles) and S. shehatae NBRC 1983 (crosses).
Data are the means ± standard deviations (error bars) of three assays.
Figure 3
Figure 3. Fermentation potentials (a) and ethanol stress tolerance (b).
Panel (a) shows the ethanol production of S. shehatae JCM 18690 (filled circles), ATY945 (open circles), ATY1112 (open triangles) and S. shehatae NBRC 1983 (crosses) from YM liquid medium containing 1% glucose. Data are the means ± standard deviations (error bars) of three assays. In panel (b), the tested strains were spotted onto YM agar medium or YM agar medium containing 7% ethanol in 10-fold serial dilutions from an initial OD600 value of 1.
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