ETHANOL PRODUCTION FROM AN INDUSTRIAL FEEDSTOCK BY IMMOBILIZED ZYMOMONAS MOBILIS IN A FLUIDIZED-BED BIOREACTOR.

The utilization of a continuous system to ferment glucose to ethanol offers considerable advantages over the traditional batch technology. Immobilization of the microorganism within gel beads prevents washout and provides high cell loadings sufficient to allow good substrate conversions at high flow rates. Thus, productivity can be greatly increased. The combination of high cell loading and rapid flow rate allows the use of nonsterile feed because free contaminants will be washed out of the system. Operation of a columnar reactor filled with the biocatalyst beads as a fluidized-bed reactor (FBR) will minimize mass transfer resistances and channeling and allow improved disengagement of the gas product, CO//2. Zymomonas mobilis has been shown to have a higher specific conversion rate and to be more efficient at ethanol fermentation than the conventional Saccharomyces cerevisiae. The response of Z. mobilis to typical unrefined industrial feedstocks, particularly the supplemental nutrients, was unknown and might be a stumbling block to commercialization. Z. mobilis immobilized in k-carrageenan beads has been shown in our laboratory to assimilate and to convert industrial feedstocks as well as the laboratory medium.