(387e) Enzymatic Bioprocessing of Biomass in NMMO and Ionic Liquids
Conversion of lignocellulosic biomass was accomplished by dissolving the biomass in the lyocell solvent, N-methylmorpholine N-oxide monohydrate (NMMO/H2O), followed by gel formation with increased water content due to pH adjustment and enzyme addition. The initial dissolution and subsequent phase separation upon dilution is similar to the commercial Tencel® fiber production in which more than 99% of the solvent is recovered due to the essential lack of vapor pressure for NMMO. Previous rheological studies by the author indicate that lignin is not soluble in NMMO/H2O and can be separated by simple filtration, whereas cellulose and hemicelluloses are soluble in NMMO/H2O as well as in the ionic liquids tested: 1-ethyl-3-methylimidazolium acetate ([Emim]Ac), 1-ethyl-3-methylimidazolium diethyl phosphate ([Emim]DEP), and 1-butyl-3-methylimidizoluim chloride ([Bmim]Cl). High cellulosic loading in the initial solvent (at least 10%w cellulose) and production rates (70 to 90% conversion) of reducing sugars are accomplished by dissolution in a modified twin screw extruder. Hydrolysis was similar in a subsequent reactor to that in the extruder equipped with recycle. The commercial enzyme mixtures (primarily Accelerase?1000 by Genencor) are more active in NMMO/H2O than in three ionic liquids tested or in aqueous systems with suspended cellulose. The commercial mixtures were composed of cellulases (exo and endo), hemicellulases and beta glucosidase. In particular, initial reaction rates are much more rapid in the gel state than in suspension due to the accessibility of the cellulose by the enzymes. NMR spectroscopy and imaging confirm the gel phase formation, phase equilibrium considerations, and diffusion characteristics. * Corresponding and presenting author
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