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Sugar Recovery and Fermentability of Hemicellulose Hydrolysates from Steam‐Exploded Softwoods Containing Bark
Author(s) -
Boussaid Abdel,
Cai Yijin,
Robinson Jamie,
Gregg David J.,
Nguyen Quang,
Saddler John N.
Publication year - 2001
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp010092b
Subject(s) - hemicellulose , hydrolysate , chemistry , steam explosion , hydrolysis , fermentation , food science , ethanol fuel , xylose , sulfuric acid , sugar , ethanol fermentation , lignin , raw material , softwood , organic chemistry , pulp and paper industry , botany , biology , engineering
The hemicellulose sugar recovery and ethanol production obtained from SO 2 ‐catalyzed steam explosion of a mixed white fir (70%) and ponderosa pine (30%) feedstock containing bark (9% dry weight/dry weight) was assessed. More than 90% of the available hemicellulose sugars could be recovered in the hydrolysate obtained after steam explosion at 195 °C, 2.38 min, and 3.91% SO 2 , with 59% of the original hemicellulose sugars detected in a monomeric form. Despite this high sugar recovery, this hydrolysate showed low ethanol yield (64% of theoretical yield) when fermented with a spent sulfite liquor‐adapted strain of Saccharomyces cerevisiae . In contrast, most hydrolysates prepared at higher steam explosion severity showed comparable or higher ethanol yields. Furthermore, the hydrolysates prepared from bark‐free feedstock showed better fermentability (87% of theoretical yield) despite containing higher concentration of known inhibitors. The ethanol yield from the hydrolysate prepared from a bark‐containing wood sample could be improved to 81% by an extra stage acid hydrolysis (121 °C for 1 h in 3% sulfuric acid). This extra stage acid hydrolysis and steam explosion at higher severity conditions seem to improve the fermentability of the hydrolysates by transforming certain inhibitory compounds present in the hydrolysates prepared from the bark‐containing feedstock and thus lowering their inhibitory effect on the yeast used for the ethanol fermentation.