Ethanol Production from Starch by Co-Immobilized Amyloglucosidase—Zymomonas Mobilis Cells in a Continuously-Stirred Bioreactor

Abstract

ABSTRACTContinuous ethanol production from starch was studied in a continuously-stirred bioreactor using co-immobilized amyloglucosidase (AMG) and Zymomonas mobilis cells. In this process, saccharification of starch and fermentation to ethanol were carried out in a single reactor.The experiments were carried out at three sets of conditions for which temperature and centrifuged cell weight were 35°C and 20.3 g; 30°C and 19.0 g; 35°C and 29.2 g, respectively. The maximum volumetric ethanol productivity (7.6 g·L−1h−1) was achieved with 0.45 g·g−1 yield at the 0.20 h−1 dilution rate at 35°C, with the initial centrifuged cell concentration of 29.2 g. The maximum ethanol concentration (43.5 g L−1) was obtained at the 0.15 h−1 dilution rate with a 96 % conversion of substrate.When experimental conditions in the reactor were compared to each other, the initial concentration of immobilized cells was found to have a significant positive influence on the kinetic parameters of ethanol fermentation.