title: Liquefaction of lignocellulose at high-solids concentrations.
abstract: To improve process economics of the lignocellulose to ethanol process a reactor system for enzymatic liquefaction and saccharification at high-solids concentrations was developed. The technology is based on free fall mixing employing a horizontally placed drum with a horizontal rotating shaft mounted with paddlers for mixing. Enzymatic liquefaction and saccharification of pretreated wheat straw was tested with up to 40% (w/w) initial DM. In less than 10 h, the structure of the material was changed from intact straw particles (length 1-5 cm) into a paste/liquid that could be pumped. Tests revealed no significant effect of mixing speed in the range 3.3-11.5 rpm on the glucose conversion after 24 h and ethanol yield after subsequent fermentation for 48 h. Low-power inputs for mixing are therefore possible. Liquefaction and saccharification for 96 h using an enzyme loading of 7 FPU/g.DM and 40% DM resulted in a glucose concentration of 86 g/kg. Experiments conducted at 2%-40% (w/w) initial DM revealed that cellulose and hemicellulose conversion decreased almost linearly with increasing DM. Performing the experiments as simultaneous saccharification and fermentation also revealed a decrease in ethanol yield at increasing initial DM. Saccharomyces cerevisiae was capable of fermenting hydrolysates up to 40% DM. The highest ethanol concentration, 48 g/kg, was obtained using 35% (w/w) DM. Liquefaction of biomass with this reactor system unlocks the possibility of 10% (w/w) ethanol in the fermentation broth in future lignocellulose to ethanol plants.
authors.affiliation: Forestry and Forest Products, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 23, DK-1958 Frederiksberg, Denmark. hnj@life.ku.dk
authors.forename: Henning
authors.initials: H
authors.lastname: Jørgensen
authors.forename: Jakob
authors.initials: J
authors.lastname: Vibe-Pedersen
authors.forename: Jan
authors.initials: J
authors.lastname: Larsen
authors.forename: Claus
authors.initials: C
authors.lastname: Felby
mesh_terms: D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D050260:Carbohydrate Metabolism; D002480:Cellulase / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D008031:Lignin / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D014242:Trichoderma / Q000378:metabolism; D014908:Triticum / Q000378:metabolism
chemical_list: C036909:lignocellulose; D000431:Ethanol; D002482:Cellulose; D008031:Lignin; D002480:Cellulase