Operability and Feasibility of Ethanol Production by Immobilized Zymomonas Mobilis in a Fluidized-Bed Bioreactor

摘要

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 (/approximately/1 to 1.5-mm-diam) of kappa-carrageenan at cell loadings of 15 to 50 g (dry wt)/L. Conversion and productivity were measured under a variety of conditions, including feedstocks, flow rates, and column sizes (up to 2.5 m tall). Volumetric productivities of 50 to 100 g EtOH/L.h have been achieved with residual glucose concentrations of less than 0.1% in the tallest fermentor. Among feeds of 10, 15, and 20% dextrose, the 15% gave the highest productivity and avoided substrate inhibition. 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 systems over conventional batch technology are discussed. 25 refs., 6 figs., 2 tabs. (ERA citation 13:032452)