Native species of spruce was debarked, cut, milled, and screened to achieve a size of less than 1 mm. The treatment was performed using 85%w/w NMMO solution at 120ºC for 1, 3, and 15 h. The pretreated wood species were then regenerated by addition of boiling distilled water, followed by vacuum filtration and washing. The pretreated and untreated wood species were enzymatically hydrolyzed by commercial cellulase (15 FPU/g) and β-glucosidase (30 IU/g) at 45°C for 96 h. Then, the hydrolyzates were fermented by a flocculation strain of Saccharomyces cerevisiae (CCUG 53310) at 30°C for 24 h.
The results showed that the pretreatment, in general, did not significantly affect the composition of the wood, while increased the yield of hydrolysis and fermentation. The cellulose hydrolysis was increased from 11% for native spruce to more than 98% for the wood treated with NMMO for 15 h, and, correspondingly, the yield of ethanol production was increased from 8.1% to over 86.1%.