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Production of Ethanol from Starch by Co-Immobilized Zymomonas mobilis-Glucoamylase in a Fluidized-Bed Reactor

  • May Y. Sun
  • Nhuan P. Nghiem
  • Brian H. Davison
  • Oren F. Webb
  • Paul R. Bienkowski
Part of the Applied Biochemistry and Biotechnology book series (ABAB)

Abstract

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 Entries

Ethanol starch Zymomonas mobilis glucoamylase simultaneous saccharification and fermentation fluidized-bed reactor 

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Copyright information

© Springer Science+Business Media New York 1998

Authors and Affiliations

  • May Y. Sun
    • 1
    • 2
  • Nhuan P. Nghiem
    • 1
  • Brian H. Davison
    • 1
    • 2
  • Oren F. Webb
    • 1
  • Paul R. Bienkowski
    • 1
    • 2
  1. 1.Bioprocessing Research and Development CenterOak Ridge National LaboratoryOak RidgeUSA
  2. 2.Department of Chemical EngineeringUniversity of TennesseeKnoxvilleUSA

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