Operability and feasibility of ethanol production by immobilizedZymomonas mobilis in a fluidized-bed bioreactor |
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Authors: | B H Davison C D Scott |
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Institution: | 1. Oak Ridge National Laboratory, TN 37831, Oak Ridge
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Abstract: | Studies have been carried out using immobilized Z.mobilis in fluidized-bed bioreactors and have emphasized operation during high productivity and conversion. The bacteria are immobilized
within small uniform beads (~1 to 1.5-mm diam) of K-carrageenan at cell loadings of 15-50 g (dry wt)/L. Conversion and productivity
were measured under a variety of conditions, including feedstocks, flow rates, temperature, pH, and column sizes (up to 2.5
m tall). Volumetric productivities of 50-120 g EtOH/h-L reactor volume have been achieved. Productivities of 60 g/h-L are
demonstrated from a 15% feed with residual glucose concentrations of less than 0.1% and 7.4% EtOH in the tallest fermentor.
Among feeds of 10, 15, and 20% dextrose, the 15% gave the highest productivity and avoided substrate inhibition. A temperature
of 30°C and pH 5 were the optimum conditions. The ethanol yield was shown to be nearly constant at 0.49 g EtOH/g glucose,
or 97% of the theoretical under a variety of conditions and transients. The biocatalyst beads have been shown to remain active
for two months. Nonsterile feed has been used for weeks without detrimental contamination. The advantages of this advanced
bioreactor system over conventional batch technology are discussed. |
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Keywords: | Index Entries" target="_blank">Index Entries Ethanol fermentation immobilized cells Zymomonas mobilis fluidized-bed reactor |
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