Simultaneous saccharification and fermentation of Jerusalem artichoke tubers to ethanol with an inulinase-hyperproducing yeast Kluyveromyces cicerisporus

Abstract:

Jerusalem artichoke tubers with inulin as major component are potential feedstock for fuel ethanol production, and Kluyveromyces cicerisporus Y179 expressing high level of inulinase is suitable for ethanol production with this feedstock by simultaneous saccharification and fermentation approach. In this article, the impact of inoculum, aeration and temperature on ethanol production by the yeast was studied. The experimental results illustrated that inoculum with different levels and seed collected at different cultivation times had negligible effect, while anaerobic conditions enhanced ethanol production, and more ethanol was produced by the yeast at 30°C than at 37°C or 42°C. The medium using Jerusalem artichoke tuber meal as sole component with 22% (W/V) total sugars was inoculated with 36 h-precultured seed at 10% (V/V), and the batch fermentation was conducted in a 5 L fermentor at 30°C with a stirring speed of 300 r/min under anaerobic conditions. After 144 h, 12.3% (V/V) ethanol was produced and the yield of ethanol from sugars was 86.9% of its theoretical one, with 93.6% sugars consumed. These results indicate that K. cicerisporus Y179 is a promising candidate for industrial ethanol production using Jerusalem artichoke tuber feedstock.

Key words:Jerusalem artichoke tubers, Kluyveromyces cicerisporus, inulinase, simultaneous saccharification and fermentation, ethanol fermentation