title: Xylose fermentation by genetically modified Saccharomyces cerevisiae 259ST in spent sulfite liquor.
abstract: Spent sulfite pulping liquor (SSL) is a high-organic content byproduct of acid bisulfite pulp manufacture which is fermented to make industrial ethanol. SSL is typically concentrated to 240 g/l (22% w/w) total solids prior to fermentation, and contains up to 24 g/l xylose and 30 g/l hexose sugars, depending upon the wood species used. The xylose present in SSL is difficult to ferment using natural xylose-fermenting yeast strains due to the presence of inhibitory compounds, such as organic acids. Using sequential batch shake flask experiments, Saccharomyces cerevisiae 259ST, which had been genetically modified to ferment xylose, was compared with the parent strain, 259A, and an SSL adapted strain, T2, for ethanol production during SSL fermentation. With an initial SSL pH of 6, without nutrient addition or SSL pretreatment, the ethanol yield ranged from 0.32 to 0.42 g ethanol/g total sugar for 259ST, compared to 0.15-0.32 g ethanol/g total sugar for non-xylose fermenting strains. For most fermentations, minimal amounts of xylitol (<1 g/l) were produced, and glycerol yields were approximately 0.12 g glycerol/g sugar consumed. By using 259ST for SSL fermentation up to 130% more ethanol can be produced compared to fermentations using non-xylose fermenting yeast.
authors.affiliation: UBC Department of Chemical and Biological Engineering, 2216 Main Mall, Vancouver, BC, Canada V6T 1Z4.
authors.forename: Steve S
authors.initials: SS
authors.lastname: Helle
authors.forename: Allison
authors.initials: A
authors.lastname: Murray
authors.forename: Janet
authors.initials: J
authors.lastname: Lam
authors.forename: David R
authors.initials: DR
authors.lastname: Cameron
authors.forename: Sheldon J B
authors.initials: SJ
authors.lastname: Duff
mesh_terms: D018533:Biomass; D019149:Bioreactors; D000431:Ethanol; D005285:Fermentation; D030781:Organisms, Genetically Modified / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*; D014994:Xylose / Q000378:metabolism*
chemical_list: D000431:Ethanol; D014994:Xylose