Abstract
Whole tree chips obtained from softwood forest thinnings were converted to ethanol via a two-stage dilute acid hydrolysis followed by yeast fermentation. The chips were first impregnated with dilute sulfuric acid, then pretreated in a steam explosion reactor to hydrolyze, more than 90% of the hemicellulose and approx 10% of the cellulose. The hydrolysate was filtered and washed with water to recover the sugars. The washed fibers were then subjected to a second acid im pregnation and hydrolysis to hydrolyze as much as 45% of the reamining cellulose. The liquors from both hydrolysates were combined and fermented to ethanol by a Saccharomyces cerevisiae yeast that had been adapted to the inhibitors. Based on available hexose sugars, ethanol yields varied from 74 to 89% of theoretical. Oligosaccharide contents higher than about 10% of the total available sugar appear to have a negative impact on ethanol yield.
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Nguyen, Q.A., Tucker, M.P., Keller, F.A. et al. Dilute acid hydrolysis of softwoods. Appl Biochem Biotechnol 77, 133–142 (1999). https://doi.org/10.1385/ABAB:77:1-3:133
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DOI: https://doi.org/10.1385/ABAB:77:1-3:133