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The effect of glucose on high-level xylose fermentations by recombinant Zymomonas in batch and fed-batch fermentations
| Content Provider | Semantic Scholar |
|---|---|
| Author | Lawford, Hugh G. Rousseau, Joyce D. |
| Copyright Year | 1999 |
| Abstract | AbstractXylose-fermenting recombinant Zymomonas mobilis has been proposed as a candidate biocatalyst for the production of fuel ethanol from cellulosic biomass and wastes. This study documents the effect of glucose on xylose utilization by recombinant Z. mobilis CP4:pZB5 using a nutrient-rich synthetic (puresugar) hardwood dilute-acid prehydrolyzate medium containing 0.8% (w/v) glucose and 4% (w/v) xylose that was enriched with respect to xylose concentration within the range 6–10% (w/v) xylose. Supplementation with glucose toafinal concentration of 2% (w/v) resulted in faster xylose utilization of both 6% and 8% xylose; however, higher levels of glucose supplementation (>2%) did not result in a decrease in the time required for fermentation of either 6% or 8% xylose. An improvement in the rate of 8% xylose utilization was also achieved through, continuous glucose feeding in which the total glucose concentration was about 1.3% (w/v). This fedbatch experiment was designed to mimic the continuous supply of glucose provided by the cellulose saccharifying enzymes in a simultaneous saccharifying and cofermentation process. The upper limit ethanol concentration at which xylose utilization by recombinant Z. mobilis CP4:pZB5 is completely inhibited is about 5.5% (w/v) at pH 5 and >6% at pH 5.75. At pH 5.75, this level of ethanol was achieved with the following media of pure sugar mixtures (each containing the same sugar loading of 12% (w/v):1.6% xylose+6% glucose;2.8% xylose+4% glucose; and3.4% xylose+8% glucose. At the level of inoculum used in this study, complete fermentation of the 12% sugar mixtures required 2–3 d (equivalent to a volumetric ethanol productivity of 0.83–1.25 g ethanol/L.h). The sugar-to-ethanol conversion efficiency was 94–96% of theoretical maximum. |
| Starting Page | 235 |
| Ending Page | 249 |
| Page Count | 15 |
| File Format | PDF HTM / HTML |
| DOI | 10.1385/ABAB:77:1-3:235 |
| Volume Number | 77 |
| Alternate Webpage(s) | http://www.gbv.de/dms/bowker/toc/9780896038240.pdf |
| Alternate Webpage(s) | https://doi.org/10.1385/ABAB%3A77%3A1-3%3A235 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
