Consolidated bioprocessing of corn cob-derived hemicellulose: engineered industrial Saccharomyces cerevisiae as efficient whole cell biocatalysts

Joana T Cunha; Aloia Romaní; Kentaro Inokuma; Björn Johansson; Tomohisa Hasunuma; Akihiko Kondo; Lucília Domingues

doi:10.1186/s13068-020-01780-2

Consolidated bioprocessing of corn cob-derived hemicellulose: engineered industrial Saccharomyces cerevisiae as efficient whole cell biocatalysts

Biotechnol Biofuels. 2020 Aug 8:13:138. doi: 10.1186/s13068-020-01780-2. eCollection 2020.

Authors

Joana T Cunha¹, Aloia Romaní¹, Kentaro Inokuma², Björn Johansson³, Tomohisa Hasunuma^{2

4}, Akihiko Kondo^{2

4}, Lucília Domingues¹

Affiliations

¹ CEB-Centre of Biological Engineering, University of Minho, Campus Gualtar, Braga, Portugal.
² Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501 Japan.
³ Center of Molecular and Environmental Biology (CBMA), University of Minho, Braga, Portugal.
⁴ Engineering Biology Research Center, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501 Japan.

Abstract

Background: Consolidated bioprocessing, which combines saccharolytic and fermentative abilities in a single microorganism, is receiving increased attention to decrease environmental and economic costs in lignocellulosic biorefineries. Nevertheless, the economic viability of lignocellulosic ethanol is also dependent of an efficient utilization of the hemicellulosic fraction, which contains xylose as a major component in concentrations that can reach up to 40% of the total biomass in hardwoods and agricultural residues. This major bottleneck is mainly due to the necessity of chemical/enzymatic treatments to hydrolyze hemicellulose into fermentable sugars and to the fact that xylose is not readily consumed by Saccharomyces cerevisiae-the most used organism for large-scale ethanol production. In this work, industrial S. cerevisiae strains, presenting robust traits such as thermotolerance and improved resistance to inhibitors, were evaluated as hosts for the cell-surface display of hemicellulolytic enzymes and optimized xylose assimilation, aiming at the development of whole-cell biocatalysts for consolidated bioprocessing of corn cob-derived hemicellulose.

Results: These modifications allowed the direct production of ethanol from non-detoxified hemicellulosic liquor obtained by hydrothermal pretreatment of corn cob, reaching an ethanol titer of 11.1 g/L corresponding to a yield of 0.328 g/g of potential xylose and glucose, without the need for external hydrolytic catalysts. Also, consolidated bioprocessing of pretreated corn cob was found to be more efficient for hemicellulosic ethanol production than simultaneous saccharification and fermentation with addition of commercial hemicellulases.

Conclusions: These results show the potential of industrial S. cerevisiae strains for the design of whole-cell biocatalysts and paves the way for the development of more efficient consolidated bioprocesses for lignocellulosic biomass valorization, further decreasing environmental and economic costs.

Keywords: Cell-surface display; Consolidated bioprocessing; Industrial Saccharomyces cerevisiae; Lignocellulosic ethanol.