Christine M. Roche, Gary A. McMillen, and Jonathan J. Stickel. National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401
The ability to screen new biomass pretreatments and advanced enzyme systems at process relevant conditions is key to developing economically viable lignocellulosic ethanol. While much research is being invested in developing pretreatment technology and enzyme systems that will more efficiently convert cellulosic biomass to sugars, there currently is no standard screening method for enzymatic saccharification of cellulosic biomass at high solids conditions. Shake flasks are the established reactor vessels used for small-scale enzymatic saccharification reactions; however, at high solids concentrations, shake flasks do not provide adequate mixing. In this work, a small-scale high solids saccharification reaction vessel was identified and a method was developed for use in screening both pretreated biomass and enzyme systems at process relevant conditions. This new method addresses mixing issues seen in high solids saccharifications. In addition, yield calculations from sugar concentrations on a mass basis were used to account for the two-phase nature of the saccharification slurry, which eliminates discontinuities in comparing high solids to low solids saccharifications that occur when using concentrations on a volume basis. In the development of this method, three small-scale vessels with various mixing modes were evaluated for their efficiency and consistency in converting high solids loadings of biomass. The method was tested and compared at bench and floor scales to determine the scalability of the reactor system.
