The next five years.
Some of you may be wondering when I'm going to grow up and do something with my life. I'm proud to announce my five year plan.
Biofuels biofuels biofuels 'glucose economy' cellulose biofuels.
I've joined Doug Clark's research group in the chemical engineering department at UC Berkeley. I'll be working on the problem of breaking down cellulose into glucose, which can be used as a feed material for microbes producing ethanol, butanol and other fuel products, polymers, chemicals, and all manner of things we need but get from oil. Cells eat up glucose, and we engineer the cells to produce the stuff we want. Here are the steps:
1. Grow plants with lots of cellulose. Plants take carbon from the air (CO2) and produce cellulose via photosynthesis.
2. Dissolve the cellulose
3. Add enzymes to break the cellulose down into sugar molecules.
4. Feed the sugar to microbes which have been engineered to produce the molecule(s) of interest
Cellulose is a long chain of glucose (sugar), all wound up and crystallized, and then stabilized with some other molecules. It's tough stuff; it has to be. Plants use it for structure and protection, so it makes sense that it's hard to break down. The dissolution and enzymatic breakdown of cellulose is widely considered the rate-limiting step in the production of biofuels from cellulose. (The ethanol plants dotting the midwest don't have to deal with cellulose - they feed the microbes using starch from corn plants. That's not very efficient, because it takes a lot of resources to produce corn, and only the kernels are used in the biofuel production. If anyone asks you to invest in a corn-based ethanol plant, tell them you got a bridge for sale...)
Ionic liquids are a special kind of solvent which have unique properties which make them able to dissolve cellulose in very high concentrations. They are essentially salts, or ions, which are liquid at room temperature. They're part organic solvent (think benzene, or methanol) and part salt (think NaCl). Their split personality allows them to wiggle between cellulose chains and pry them apart, dissolving them and breaking down their crystalline structure. This makes them much more susceptible to attack by enzymes converting the cellulose to sugar.
Problem is, these cellulase enzymes evolved in water, not in ionic liquids. In order to use enzymes to break down the cellulose that we dissolve in ionic liquids, we have to precipitate the cellulose out of the ionic liquid solution and put it back in water. My research project will involve trying to understand how the properties of the ionic liquids affect enzyme activity, and to engineer new enzymes that are active in ionic liquids.
Or at least what I think I'm doing. I'll let you know in a year or two if things turn out that way.