Direct production of bioethanol from Jerusalem artichoke inulin by gene-engineering Saccharomyces cerevisiae 6525 with exoinulinase gene

Abstract

Jerusalem artichoke (Helianthus tuberosus L.), an important crop, containing over 50% inulin in its tubers on a dry weight basis is an agricultural and industrial crop with a great potential for production of ethanol and industrial products. Inulin is a good substrate for bioethanol production. Saccharomyces cerevisiae 6525 can produce high concentrations of ethanol, but it cannot synthesize inulinase. In this study, a new integration vector carrying inuA1 gene encoding exoinulinase was constructed and transformed into 18SrDNA site of industrial strain S. cerevisiae 6525. The obtained transformant, BR8, produced 1.1 U mL^− 1 inulinase activity within 72 h and the dry cell weight reached 12.3 g L^− 1 within 48 h. In a small-scale fermentation, BR8 produced 9.5% (v/v) ethanol, with a productivity rate of 0.385 g ethanol per gram inulin, while wild-type S. cerevisiae 6525 produced only 3.3% (v/v) ethanol in the same conditions. In a 5-L fermentation, BR8 produced 14.0% (v/v) ethanol in fermentation medium containing inulin and 1% (w/v) (NH4)₂SO₄. The engineered S. cerevisiae 6525 carrying inuA1 converted pure nonhydrolyzed inulin directly into high concentrations of ethanol.

Keywords::

• Bioethanol
• Jerusalem artichoke
• inulinase
• Saccharomyces cerevisiae
• gene engineering

Additional information

Funding

Funding

The authors are grateful for the financial support of the National Key Project of Scientific and Technical Supporting Programs funded by Ministry of Science & Technology of China [grant no. 2011BAD13B09]; the National Key Project of Scientific and Technical Supporting Programs funded by Ministry of Science & Technology of Jiangsu Province [grant no. BE2011368]; the Fundamental Research Funds for the Central Universities [grant no.Y0201100249]; the Project of Special Fund for Public Welfare Industrial (Agriculture) Research of China [grant no. 200903001-5]; One Hundred-Talent Plan of Chinese Academy of Sciences (CAS), the Science and Technology Development Plan of Shandong Province [grant no. 2010GSF10208]; and the Yantai Science and Technology Development Project [grant no. 2011016].