This Small Business Technology Transfer (STTR) Phase I project proposes to develop a new low-cost platform for the production of methyl ethyl ketone directly from pretreated cellulosic biomass in a single step using a novel recombinant cellulolytic Bacillus subtilis strain. Methyl ethyl ketone (MEK), also referred to as 2-butanone, is the second most important commercial ketone after acetone. MEK is currently only produced by the oxidation of 2-butanol. However, this industrial synthesis process uses starting materials derived from petrochemicals and is generally expensive as well as not environmentally friendly. There is an urgent need to develop a novel cost-effective and environmentally friendly method to produce MEK other than through 2-butanol. The cellulosic biomass is the most abundant natural renewable resource and has great potential for the production of valuable biocommodities for both short- and long-term sustainability. However, the process for converting non-food lignocellulosic material into MEK is not yet economically feasible due to the high cost of the cellulase involved in cellulose hydrolysis and the use of fastidious culture media. Using synthetic pathway and metabolic engineering, this project will convert noncellulose-utilizing B. subtilis into an efficient cellulose utilizer to produce MEK with high yield and titer, suitable for industrial fermentation. The broader impact/commercial potential of this project, if successful, will be a low-cost platform for producing MEK from nonfood biomass in a process called consolidated bioprocessing. MEK may then be used as a solvent for paint, and serve as an intermediate in the production of other chemicals. Therefore, MEK could easily find a market in the paint industry and in plastics manufacturing. More importantly, MEK could be converted by subsequent hydrogenation into octane isomers that can be used to produce high-grade aviation fuel. Currently, MEK is synthesized from petroleum-derived chemicals via a method involving greenhouse gas emissions. So far, few efforts have been made to produce bio-based MEK due to low process economics. The proposed recombinant cellulolytic B. subtilis would have advantages over developing other microorganisms. In addition, the novel green technology will satisfy operational cost considerations, environmental concerns, and health and safety regulations. Compared to traditional mechanism, this novel route will be more cost-effective and environmentally friendly. If successfully commercialized after the completion of the Phase II project, this bio-based MEK production technology will have a significant competitive advantage over traditional methods because it is more commercially attractive and supports sustainable societal development.
