ALTERNATIVE ENERGY:

SUMMARY: Switchgrass has been genetically modified into a more useful fuel, but this research should not see the light of day until it's proven to be safe for the environment.

Nuclear fusion, i.e. the physical process that powers stars, is the only realistic, long-term solution to the energy needs of modern civilization. Until this most critical research project of our time is ready for practical, large-scale deployment, and until scientists and engineers figure out how to realistically use hydrogen as a portable energy storage medium, biofuels are a realistic transitional source of energy.

Switchgrass, a hardy plant native to North America, is a realistic plant source for the United States and Canada (it can yield several times the amount of energy placed into its cultivation). Unfortunately, switchgrass is a bit too hardy.

In other words, harsh conditions are generally required to break apart the sugar polymers into useful small molecules. This challenge has been addressed through multiple approaches, e.g. the hunt for rugged enzymes compatible with an industrial decomposition reactor.

Richard Dixon, Zeng-Yu Wang (Samuel Roberts Noble Foundation, United States), and coworkers have made a contribution to the switchgrass decomposition challenge. They have genetically modified the lignin in switchgrass to effect enhanced ethanol yields with reduced processing costs; whether this development should ever be put to use is another question altogether.

Improving switchgrass for biofuel production.

The scientists genetically modified switchgrass to reduce (by over 90%) expression of the caffeic acid 3-O-methyltransferase (COMT) gene. This modification reduced switchgrass lignin content by approximately 10%.

Cellulose structure and content (critical to plant integrity) wasn't much affected. The plants generally grew and developed normally (large COMT downregulation imparted a brown-red color to the stem).

Heating to less than 190°C in dilute sulfuric acid ("mild" conditions), followed by fermentation, resulted in a per-gram ethanol yield 25% and above that of "normal" switchgrass, and this increased yield trend generally held until the most severe processing conditions were used. The sugar polymers in the transgenic switchgrass are more susceptible to chemical breakdown.

The transgenic switchgrass required a fourth to a third fewer enymes after acid pretreatment for final ethanol production, to yield similar amounts of ethanol. Furthermore, it yielded 18% more fermentation products, with 50% less unreacted cellulose remaining.

Overall evaluation.

This is clearly a unique approach to render switchgrass into a somewhat environmentally-friendly fuel. On the other hand, I'm not convinced that genetically modifying switchgrass, and planting it on a large scale, is a good idea.

Transgenic switchgrass is more dangerous than transgenic corn; the former will grow without irrigation, and will quickly spread throughout the ecosystem. Scientists must clearly demonstrate that this biofuel crop is environmentally benign.

Such thorough testing will take years to execute. Consequently, I personally (respectfully) feel that transgenic switchgrass is an environmentally irresponsible approach to biofuel production.

NOTE: The scientists' research was funded by the US Department of Agriculture, the US Department of Energy, the BioEnergy Science Center, and the Samuel Roberts Noble Foundation. A possible conflict of interest is that the two corresponding authors are employed by the Samuel Roberts Noble Foundation (i.e. one of the funders of this research).

Fu, C., Mielenz, J. R., Xiao, X., Ge, Y., Hamilton, C. Y., Rodriguez Jr, M., Chen,F., Foston, M., Ragauskas, A., Bouton, J., Dixon, R. A., & Wang, Z.-Y. (2011). Genetic manipulation of lignin reduces recalcitrance and improves ethanol production from switchgrass Proceedings of the National Academy of Sciences : 10.1073/pnas.1100310108