Continuous ethanol production and cell growth in an immobilized-cell bioreactor employing Zymomonas mobilis.
Ethanol-producing bioreactors employing cells of Zymomonas mobilis attached to glass-fiber pads were operated continuously for as long as 28 days. Ethanol production, which is related to bed-associated biomass levels, was found to occur in three distinct phases: an exponential phase, a linear phase, and a "steady-state" phase. After prolonged operation, a bacterial floc developed in the reactor. The maximum effluent ethanol concentration and the maximum volumetric productivity were 6.4% and 152 g L(-1) h(-1), respectively, and both were attained at a liquid residence time of from 10-15 min. Both maxima occurred after the development of the bacterial floc. The flocculant bacterium has been isolated and tentatively identified as a flocculant strain of Z. mobilis.
Chemical Technology Division, Oak Ridge National Laboratory, Operated by Union Carbide Corporation under contract W-7405-eng-26 with the U.S. Department of Energy. Oak Ridge, Tennessee 37830.
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