<p>Detoxification of dilute-acid lignocellulose hydrolysates by treatment with Ca(OH)<sub>2 </sub>(overliming) efficiently improves the production of fuel ethanol, but is associated with drawbacks like sugar degradation and CaSO<sub>4</sub> precipitation. In factorial designed experiments, in which pH and temperature were varied, dilute-acid spruce hydrolysates were treated with Ca(OH)<sub>2</sub>, NH<sub>4</sub>OH or NaOH. The concentrations of sugars and inhibitory compounds were measured before and after the treatments. The fermentability was examined using the yeast <em>Saccharomyces cerevisiae</em> and compared with reference fermentations of synthetic medium without inhibitors. The treatment conditions were evaluated by comparing the balanced ethanol yield, which takes both the degradation of sugars and the ethanol production into account. Treatment conditions resulting in excellent fermentability and minimal sugar degradation were possible to find regardless of whether Ca(OH)<sub>2</sub>, NH<sub>4</sub>OH or NaOH was used. Balanced ethanol yields higher than those of the reference fermentations were achieved for hydrolysates treated with all three types of alkali. As expected, treatment with Ca(OH)<sub>2</sub> gave rise to precipitated CaSO<sub>4</sub>. The NH<sub>4</sub>OH treatments gave rise to a brownish precipitate but the amounts of precipitate formed were relatively small. No precipitate was observed in treatments with NaOH. The possibility that the ammonium ions from the NH<sub>4</sub>OH treatments gave a positive effect as an extra source of nitrogen during the fermentations was excluded after experiments in which NH<sub>4</sub>Cl was added to the medium. The findings presented can be used to improve the effectiveness of alkali detoxification of lignocellulose hydrolysates and to minimize problems with sugar degradation and formation of precipitates.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:kau-2632 |
| Date | January 2006 |
| Creators | Alriksson, Björn |
| Publisher | Karlstad University, Faculty of Technology and Science, Karlstad : Karlstads universitet |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, text |
| Relation | Karlstad University Studies, 1403-8099 ; 2006:30 |
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