Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
Hydrolysis and fermentation at high solids concentration (>20% DM) has several advantages economically. Less water is required meaning less waste water produced, and the final ethanol yield increases requiring less energy for distillation. Unfortunately, using high solids also has its disadvantages in the process such as product inhibition due to rapid accumulation of glucose. It is therefore preferably to run the process as SSF, but due to the high consistency it is challenging to mix the biomass to a homogenous slurry. To avoid problems with mixing, a liquefaction step (pre-hydrolysis) is added before SSF, with the purpose of reducing the viscosity of the biomass to an extent where it is pumpable. The liquefaction step should be as short and efficient as possible, which can be done with the right combination of cellulases. Thermostable enzymes have several benefits as liquefying cellulases. When increasing temperature, the reaction rate increases and the liquefaction time can be shortened.
In this study, the hydrolysis yield at high DM (25%) using mesophilic, commercial enzyme mixtures and novel thermophilic monocomponents were investigated. The synergy and hydrolysis yield of mesophilic and thermophilic endoglucanase supplemented with β-glucosidases were measured. Enzyme mixtures were tested at both optimum temperature for the mesophilic enzymes and optimum temperature for the thermophilic enzymes. During liquefaction and hydrolysis, monosaccharides, reducing ends, and water insoluble solids (WIS) were measured. In addition, the reduction in viscosity was measured for the most efficient combinations of enzymes during hydrolysis.