Production of Ethanol from Starch by Co-Immobilized Zymomonas mobilis-Glucoamylase in a Fluidized-Bed Reactor
The production of ethanol from starch was studied in a fluidized-bed reactor (FBR) using co-immobilized Zymomonas mobilis and glucoamylase. The FBR was a glass column of 2.54 cm in diameter and 120 cm in length. The Z. mobilis and glucoamylase were co-immobilized within small uniform beads (1.2-2.5 mm diameter) of K-carrageenan. The substrate for ethanol production was a soluble starch. Light steep water was used as the complex nutrient source. The experiments were performed at 35°C and pH range of 4.0-5.5. The substrate concentrations ranged from 40 to 185 g/L, and the feed rates from 10 to 37 mL/min. Under relaxed sterility conditions, the FBR was successfully operated for a period of 22 d, during which no contamination or structural failure of the biocatalyst beads was observed. Volumetric productivity as high as 38 g ethanol/(Lh), which was 74% of the maximum expected value, was obtained. Typical ethanol volumetric productivity was in the range of 15-20 g/(Lh). The average yield was 0.49 g ethanol/g substrate consumed, which was 90% of the theoretical yield. Very low levels of glucose were observed in the reactor, indicating that starch hydrolysis was the rate-limiting step.
Index EntriesEthanol starch Zymomonas mobilis glucoamylase simultaneous saccharification and fermentation fluidized-bed reactor
Unable to display preview. Download preview PDF.
- 2.Godia, F., Casas, C., and Sola, C. (1987), Process Biochem., 22, 43–48.Google Scholar
- 4.Lee, G. M., Kim, C. H., Mohammed, Z. A., Han, M. H., and Rhee, S. K. (1987), J. Chem. Tech. Biotechnol., 38, 235–242.Google Scholar
- 12.Sun, M. Y., Davison, B. H., Bienkowski, P. R., Nghiem, N. P., and Webb, O. F., (1997), Poster presented at the 213th National Meeting of the American Chemical Society, San Francisco, CA.Google Scholar