Navy Enlists Microbes To Cut Costs

With funding from ONR's Green Synthesis of Energetic Materials program, microbiologist John Frost and his team at Michigan State University created strains of microbes that convert certain types of sugars into a non-natural synthetic material, called butanetriol. The Navy depends on the slightly yellow liquid to produce the propellant BTTN (butanetriol trinitrate), which is used in some missiles, including the Hellfire.

Biologist and ONR program officer Harold Bright initiated the green project three years ago when he learned that chemists at the Navy Surface Warfare Center in Indian Head, Md., couldn't afford adequate supplies of chemically-produced butanetriol. To fill the gap they use nitroglycerin, which is less expensive but more sensitive to physical shocks and temperature changes.

Currently, butanetriol costs $30 to $40 per pound, and together the Navy and Army purchase about 15,000 pounds per year. If the costs could be reduced to $10 or $15 per pound, Indian Head estimates the services' demand could rise to 180,000 pounds per year, replacing nitroglycerin in a number of current and new applications.

Bright adds, "This is a biology-unique process that in terms of environmental cleanliness and costs, chemists cannot match. Eventually, this 'green' production method will be applied to other materials, as we move away from petroleum-based processes that are environmentally 'dirty' and therefore expensive."

As they explain in the October issue of the Journal of the American Chemical Society, the researchers at Michigan State manipulated the DNA of Escherichia coli and Pseudomonas fragi so that the bacteria would act like minifactories, spewing out butanetriol as they go about their normal life functions. This process is "at the cutting edge of both civilian and military science," explains Bright.

In contrast to the high-pressure, high-temperature chemical process to produce butanetriol, the microbes require only air, sugar, and salts in a warm-water environment. Once they've produced the butanetriol and lived out their lives, they are killed and then disposed of in a standard municipal sewage treatment facility.

As an added bonus, butanetriol is also a precursor to two cholesterol-lowering drugs. Says Frost, "This is a classic example of dual use for molecules between pharmaceutical and defense applications."