Although ethanol for transport biofuel applications is still largely produced using “first generation biofuel feedstocks” (such as corn, and sugarcane), many see “cellulose ethanol”, or ethanol from cellulosic biomass (a “second generation” biofuel crop) as the bioethanol of the future. Many studies have shown that cellulose ethanol has a better net energy yield and a better GHG (greenhouse gas) balance compared to corn ethanol. However, cellulose ethanol production technology (via the biochemical route) still has some hurdles that limit cost-effective applications on a large scale such as the identification of effective cellulases. Cellulases are enzymes which break down the cellulose into simple sugars that can be fermented into ethanol. Frances Arnold, a scientist from the California Institute of Technology (Caltech), in the United States, aims to develop new cost effective cellulases, by using a tool called, “directed evolution”. This tool is described as a method of protein engineering that “harnesses Darwinian selection to evolve proteins or RNA with desirable properties not found in nature” (wikipedia.org). It may involve creating variations of the gene that codes for cellulases, inserting the mutated cellulase genes into a microorganism, and then screening it for a particular/desired characteristic..