Construction of bioengineered yeast platform for direct bioethanol production from alginate and mannitol

• Published in: Applied microbiology and biotechnology Vol. 101; no. 17; pp. 6627 - 6636
• Main Authors: Takagi, Toshiyuki, Sasaki, Yusuke, Motone, Keisuke, Shibata, Toshiyuki, Tanaka, Reiji, Miyake, Hideo, Mori, Tetsushi, Kuroda, Kouichi, Ueda, Mitsuyoshi
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2017; Springer; Springer Nature B.V
• Subjects: Algae; Alginate chemicals; Alginic acid; Baking yeast; Bioconversion; Bioengineering; Biofuels; Biomedical and Life Sciences; Biotechnological Products and Process Engineering; Biotechnology; Carbohydrates; Carbon sources; Cell culture; Cellulose; Chemical properties; Construction standards; Ecosystems; Ethanol; Fermentation; Genomes; Hemicellulose; Integration; Laminarin; Life Sciences; Lignin; Mannitol; Marine ecosystems; Microbial Genetics and Genomics; Microbiology; Production processes; Saccharomyces cerevisiae; Seaweeds; Sugar; Uronic acid; Yeast; Yeasts; Yeasts (Fungi); Brown macroalgae; Alginate; Bioethanol; Yeast cell surface engineering; Mannitol; Saccharomyces cerevisiae
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-017-8418-y

Brown macroalgae are a sustainable and promising source for bioethanol production because they are abundant in ocean ecosystems and contain negligible quantities of lignin. Brown macroalgae contain cellulose, hemicellulose, mannitol, laminarin, and alginate as major carbohydrates. Among these carbohydrates, brown macroalgae are characterized by high levels of alginate and mannitol. The direct bioconversion of alginate and mannitol into ethanol requires extensive bioengineering of assimilation processes in the standard industrial microbe Saccharomyces cerevisiae. Here, we constructed an alginate-assimilating S. cerevisiae recombinant strain by genome integration and overexpression of the genes encoding endo- and exo-type alginate lyases, DEH (4-deoxy- l -erythro-5-hexoseulose uronic acid) transporter, and components of the DEH metabolic pathway . Furthermore, the mannitol-metabolizing capacity of S. cerevisiae was enhanced by prolonged culture in a medium containing mannitol as the sole carbon source. When the constructed strain AM1 was anaerobically cultivated in a fermentation medium containing 6% ( w / v ) total sugars (approximately 1:2 ratio of alginate/mannitol), it directly produced ethanol from alginate and mannitol, giving 8.8 g/L ethanol and yields of up to 32% of the maximum theoretical yield from consumed sugars. These results indicate that all major carbohydrates of brown macroalgae can be directly converted into bioethanol by S. cerevisiae . This strain and system could provide a platform for the complete utilization of brown macroalgae.