Abstract
Xylose-fermenting recombinant bacteria and recombinant and wild-type yeasts are being examined for use in large-scale hemicellulose conversion processes for the production of fuel ethanol. Significant differences in xylose metabolism exist between these microorganisms, however, and different factors influence their fermentative performance. For comparison, this chapter provides a summary ofrepresentative performance data for xylose fermentation carried out using synthetic media. Performance data achieved on detoxified hydrolyzates also are summarized for the two microorganisms for which the most performance data are available, recombinant Escherichia coli bacteria and xylose-fermenting Pichia stipitis yeast. The discussion focuses on the significant influence that hydrolyzatecomposition, particularly the levels and types of carbohydrates and indibitory components, has on processing requirements and operating characteristics. This analysis suggests that recombinant ethanologenic enteric bacteria are superior to wild-type yeast in two key attributes: substrate range and tolerance to inhibitory components. Hower, given the rate of progress in developingxylose-fermenting strains of Saccharomyces cerevisiae and Zymomonas mobilis, it is undertain how long recombinant enteric bacteria will remain the front-runners for use in large-scale conversion processes. Regardless of which type of microorganism is used, hydrolyzates generally must be detoxified to achieve favorable bioconversion performance. It is therefore recommended that priority be givento studying the feasibiliy of incorporating detoxification treatments into an integrated ethanol-from-biomass process.
| Original language | American English |
|---|---|
| Title of host publication | Handbook on Bioethanol: Production and Utilization |
| Editors | C. E. Wyman |
| Pages | 287-313 |
| State | Published - 1996 |
NREL Publication Number
- NREL/CH-420-6713