genes, with computer assistance, to perform specific reactions and then synthesizing the desired genes for insertion into microbes. Yeasts can also be engineered to produce larger amounts of lipids, which with additional metabolic engineering can be converted to useful products—potentially, fuels. Using these techniques, it is possible that properly designed hydrocarbon products in either the diesel or the gasoline range would not require significant refining and could fit directly into the existing infrastructure.

Although none of these processes is approaching commercial production at this point, the level of activity and the current rate of progress could change that status in the not-too-distant future. Several companies are employing synthetic biology to create bacteria that produce increased amounts of fatty acids or other lipids that are then converted to hydrocarbons of virtually any length or structure desired. Moreover, the hydrocarbons phase-separate from the growth medium, thereby markedly reducing separation costs. The feedstock for the bacteria is renewable sugars, which can be obtained from sugar cane, grain, or cellulosic biomass (LS9, 2008). It is difficult to project the future of these and other nascent developments, but they deserve careful watching.

Technologies to Improve Biochemical Conversion

Significant advances are being made in the areas of genomics, molecular breeding, synthetic biology, and metabolic and bioprocess engineering that will likely enable innovation and advancement in the development of alternative transportation fuels. These and related technologies have the potential to greatly accelerate the creation of dedicated or dual-purpose energy crops as well as of microorganisms useful both for feedstock-conversion processes and biofuel production.

Genomics

The sequencing of full genomes continues to become faster and less costly, thus allowing energy crops such as tree species, perennial grasses, and nonedible oil seeds (castor and jatropha, for example) to be sequenced. The resulting data are extremely important for improving overall yields, for enabling improved nutrient and water utilization, and for understanding and manipulating biochemical pathways to enhance the production of desired products.

The sequencing data also have other uses. They can be used to target specific genes for downregulation by classical methods such as antisense and RNA interference, but also via complete inactivation using new and evolving procedures for



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement