Genencor is engaged in developing an Accellerase® line of enzymes for ligno-cellulosic biomass conversion, and we will discuss some of the recent enzyme improvements made. In reducing the cost of enzymes for biomass conversion it is also important to make improvements in how these enzymes are used, and we are actively involved in process window optimization with customers. Design of Experiment (DoE) modeling will be illustrated as a powerful tool in process development for enzymatic biomass conversion (e.g. saccharification, and simultaneous saccharification and fermentation, SSF), using Genencor’s latest Accellerase® biomass enzymes. It is generally observed that enzymatic saccharification decreases with increasing biomass slurry concentrations but, for a commercially realistic process, it is necessary to operate at high dry solids loading for the highest potential sugar concentration and, consequently, ethanol concentration. In this presentation, the effects of initial solids loading, enzyme loading, and time on the ethanol concentration and ethanol yield will be studied. The validity of the prediction of the DoE model, including in scale-up, will be presented, as will examples of conversion process design options.