Ethanol Production from Glucose and Xylose by Immobilized Zymomonas mobilis CP4(pZB5)
Fermentation of glucose-xylose mixtures to ethanol was investigated in batch and continuous experiments using immobilized recombinant Zymomonas mobilis CP4(pZB5). This microorganism was immobilized by entrapment in k-carrageenan beads having a diameter of 1.5-2.5 mm. Batch experiments showed that the immobilized cells co-fermented glucose and xylose to ethanol and that the presence of glucose improved the xylose utilization rate. Batch fermentation of rice straw hydrolyzate containing 76 g/L glucose and 33.8 g/L xylose gave an ethanol concentration of 44.3 g/L after 24 hours, corresponding to a yeild of 0.46 g ethanol/g sugars. Comparable results were achieved with a synthetic sugar control. Continuous fermentation runs were performed in a laboratory scale fluidized-bed bioreactor (FBR). Glucose-xylose feed mixtures were run through the FBR at residence times of 2 to 4 hours. Glucose conversion to ethanol was maintained above 98% in all continuous runs. Xylose conversion to ethanol was highest at 91.5% for a feed containing 50 g/L glucose-13 g/L xylose at a dilution rate of 0.24 h-1. The xylose conversion to ethanol decreased with increasing feed xylose concentration, dilution rate and age of the immobilized cells. Volumetric ethanol productivities in the range of 6.5 to 15.3 g/L-h were obtained.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Transportation Technologies (EE-30)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 6930
- Report Number(s):
- ORNL/CP-103176; EB 52 01 00 0; ON: DE00006930
- Resource Relation:
- Conference: 21st Sympsoium on Biotechnology for Fuels and Chemicals, Ft. Collins, CO, May 2-6, 1999
- Country of Publication:
- United States
- Language:
- English
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