UCLA researchers examine the potential of algae proteins as Biofuel

At present, most of feedstock used for biofuel production is either carbohydrate for producing various alcohol fuels or lipid for producing biodiesel. However, the possibilities for using proteins to produce biofuel had not been much explored. The UCLA research project found that there is potential for proteins to be used as biofuel and doing so would result in environmental benefits. The paper was published online in the journal Nature Biotechnology. The team is currently looking at ways to develop large scale systems and extract protein economically.

UCLA Engineering research scientist, Kwang Myung Cho;

"Proteins had been completely ignored as a potential biomaterial because they've been thought of mainly as food. But in fact, there are a lot of different proteins that cannot be used as food. These proteins were overlooked as a resource for fuel or for chemicals because people did not know how to utilize them or how to grow them. We've solved these problems."

"This research is the first attempt to utilize protein as a carbon source for energy production and biorefining. To utilize protein as a carbon source, complex cellular regulation in nitrogen metabolism had to be rewired. This study clearly showed how to engineer microbial cells to control their cellular nitrogen metabolism."

Proteins are very common in nature; alongside lipids and carbohydrates they are some of the most abundant biomolecules in the world. When fast growing micro-organisms are growing in a nutrient rich conditions (such as in a bioreactor), proteins make up the largest portion of the cell mass and accumulate quickly, lending itself well to production in continuous systems. Protein can also be easily digested by microbes, making the preprocessing steps for fermentation simpler. Typically, the proteins would by broken down into its constituent units and then converted into chemicals. However, this step happens to present the greatest challenge. Most bacteria don’t convert their proteins into other chemicals under normal conditions; they retain them as protein or recycle them and re-use the subunits.

This challenge was met by reprogramming the way the cell handles protein; they used an existing cellular mechanism to export ammonia and carbon sources that can be used to produce fuel from the cell. Regulation of how the cell uses proteins for growth was altered, so that the cell would degrade protein without using it for growth. The ammonia is recycled and used as fertilizer for the algae bioreactor, to be incorporated into proteins to be recycled again. This strategy can be tweaked to fix more CO2 from the environment and to achieve higher yields of algae.   

An interesting point was made by the research group on nitrogen pollution; nitrogen fertilizers are a well known cause of ecological damage but in a system such as the one this group is considering nitrogen run off would not be an issue. Also, in the natural environment exposure to various conditions nitrogen containing residues (which are produced by other fermentation processes) can be converted into nitrous oxide, a greenhouse gas which is 300 times more potent than CO2. The ability to utilize the protein content of feedstock in addition to the carbohydrate/lipid content for generating biofuel would allow biofuel to be produced more efficiently, therefore decreasing the area of land that is needed to grow energy crops to meet demand for fuel.