ABSTRACT
Among the many types of lignocellulosic biomass pretreatment methods, the use of ionic liquids (ILs) is regarded as one of the most promising strategies. In this study, the effects of four kinds of ILs for pretreatment of lignocellulosic biomass such as bagasse, eucalyptus, and cedar were evaluated. In direct ethanol fermentation from biomass incorporated with ILs by cellulase-displaying yeast, 1-butyl-3-methylimidazolium acetate ([Bmim][OAc]) was the most effective IL. The ethanol production and yield from [Bmim][OAc]-pretreated bagasse reached 0.81 g/L and 73.4% of the theoretical yield after fermentation for 96 h. The results prove the initial concept, in which the direct fermentation from lignocellulosic biomass effectively promoted by the pretreatment with IL.
Subject(s)
Biofuels , Ethanol/metabolism , Glucose/biosynthesis , Imidazoles/chemistry , Ionic Liquids/chemistry , Lignin/metabolism , Xylose/biosynthesis , Aspergillus/drug effects , Aspergillus/enzymology , Biomass , Cedrus/chemistry , Cellulases/metabolism , Cellulose/chemistry , Eucalyptus/chemistry , Fermentation , Fungal Proteins/metabolism , Imidazoles/pharmacology , Ionic Liquids/pharmacology , Kinetics , Saccharomyces cerevisiae/drug effects , Saccharomyces cerevisiae/enzymology , Trichoderma/drug effects , Trichoderma/enzymologyABSTRACT
The potential of 1-hexylpyridinium chloride ([Hpy][Cl]), to pretreat cellulosic feedstocks was investigated using microcrystalline cellulose (Avicel) and Bagasse at 80 °C or 100 °C. Short [Hpy][Cl] pretreatments, <30 min, at lower temperature accelerate subsequent enzymatic saccharification of Avicel. Over 95% conversion of pretreated Avicel to glucose was attained after 24h enzymatic saccharification under optimal conditions, whereas regenerated Bagasse showed 1-3-fold higher conversion than untreated biomass. FT-IR analysis of both Avicel and Bagasse samples pretreated with [Hpy][Cl] or 1-ethyl-3-methyimidazolium acetate ([Emim][OAc]) revealed that these ionic liquids behaved differently during pretreatment. [Hpy][Cl] pretreatment for an extended duration (180 min) released mono- and disaccharides without using cellulase enzymes, suggesting [Hpy][Cl] has capability for direct saccharification of cellulosic feedstocks. On the basis of the results obtained, [Hpy][Cl] pretreatment enhanced initial reaction rates in enzymatic saccharification by either crystalline polymorphic alteration of cellulose or partial degradation of the crystalline cellulosic fraction in biomass.
Subject(s)
Biomass , Carbohydrate Metabolism/drug effects , Cellulase/metabolism , Cellulose/metabolism , Ionic Liquids/pharmacology , Pyridinium Compounds/pharmacology , Transition Temperature , Lignin/analysis , RecyclingABSTRACT
The potential of 1-buthyl-3-methylpyridinium chloride, [Bmpy][Cl], as a pretreatment solvent for lignocellulosic biomasses, Bagasse and Eucalyptus, was investigated. The yields of regenerated biomasses ranged between 35% and 96%, and varied according to the pretreatment time, type of ionic liquid (IL) and biomass. The pretreatment of the biomass with [Bmpy][Cl] resulted in up to 8-fold increase in the cellulose conversion when compared with the untreated biomass. For a short pretreatment period (i.e., 10 min), [Bmpy][Cl] showed better performance than 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) with respect to the initial enzymatic saccharification rates. The increase in the reaction rates with [Emim][OAc] treatment was because of a reduction in the cellulose crystallinity. In contrast, a decrease in the crystallinity index was not clearly observed for the biomass pretreated with [Bmpy][Cl], and the enhancement of the enzymatic saccharification rates using this IL is presumably due to a reduction in the degree of polymerization of cellulose in the biomass.
