Sunday, April 29, 2007

Improving hydrolysis of poorly pretreated biomass by rough mixing scaled to the laboratory

K.C. McFarland and Joel R. Cherry. Novozymes, Inc., 1445 Drew Ave., Davis, CA 95618

The processes necessary for conversion of biomass to sugars or ethanol are currently being scaled from laboratory to pilot plant, with mixed results.  Some mild pretreatments are insufficient for efficient enzymatic hydrolysis under current laboratory methods.  We present a laboratory scale model for improved mixing that demonstrates benefit for high solids content and poorly pretreated samples.

 Standard testing of enzyme hydrolysis of biomass is most often performed in shake flasks with orbital mixing (NREL LAP-009).  Mixing of high solids content or poorly treated biomass represents a challenge for orbital mixing.  This is sometimes addressed by impellers more suitable for low viscosity liquids or by lift-and-drop mechanisms (e.g. cement mixers) not scaled for the laboratory.  We built a small and inexpensive tumbler that is analogous to efficient lift-and-drop systems for testing enzyme hydrolysis simultaneously on multiple samples, and demonstrated that poorly treated biomass is more efficiently hydrolyzed by rough mixing than by the standard laboratory process.