title: Microwave-assisted pretreatment of recalcitrant softwood in aqueous glycerol.
abstract: Microwave-assisted pretreatment of recalcitrant softwood in aqueous glycerol containing a series of organic and inorganic acids with different pK(a) values was examined. The pulp obtained by organosolvolysis with 0.1% hydrochloric acid (pK(a) -6) at 180 degrees C for 6 min gave the highest sugar yield, 53.1%, based on the weight of original biomass. The pretreatment efficiency correlated linearly with the pK(a) of the acids, with the exception of malonic and phosphoric acids. Organosolvolysis with 1.0% phosphoric acid (pK(a) 2.15) gave a saccharification yield (50.6%) higher than that expected from its pK(a), while the catalytic effect of malonic acid (pK(a) 2.83) was negligible. Extensive exposure of crystalline and non-crystalline cellulose by the glycerolysis with strong inorganic acids was demonstrated by using fluorescent-labeled recombinant carbohydrate-binding modules (CBMs). Because of the low concentration of the acid catalysts and availability of glycerol as a by-product from biodiesel and fatty acid production, organosolvolysis in glycerol is an appealing process for pretreatment of recalcitrant softwood.
authors.affiliation: Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.forename: Rie
authors.initials: R
authors.lastname: Takada
authors.forename: Shuichi
authors.initials: S
authors.lastname: Karita
authors.forename: Takahito
authors.initials: T
authors.lastname: Watanabe
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Honda
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D000143:Acids / Q000737:chemistry; D002241:Carbohydrates / Q000737:chemistry; D028203:Cedrus / Q000737:chemistry*; D002482:Cellulose / Q000032:analysis; D003460:Crystallization; D005453:Fluorescence; D005990:Glycerol / Q000737:chemistry*; D008872:Microwaves; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry*; D014934:Wood / Q000737:chemistry*; D014990:Xylans / Q000032:analysis
chemical_list: D000143:Acids; D002241:Carbohydrates; D012997:Solvents; D014990:Xylans; D014867:Water; D002482:Cellulose; D005990:Glycerol