Building miniature greenhouses for experiments on the International Space Station has led to the invention of a device that can destroy Anthrax -- a bacteria that can be deadly when inhaled.

The Anthrax-killing air scrubber, called AiroCideTiO2 (titanium dioxide), is a tabletop-size metal box that bolts to office ceilings or walls. Its fans draw in airborne spores and airflow forces them through a maze of tubes. Inside, hydroxyl radicals attack and kill pathogens. Most remaining spores are destroyed by high-energy ultraviolet photons.

AiroCideTiO2, an anthrax-killing device manufactured by KES Science and Technology Inc., in Kennesaw, Ga., looks like a square, metal box when it is installed on an office wall. Photo: NASA/MSFC/T. Leibold

The technology to build the device emerged from another product called Bio-KES, which today is used by grocers and florists to remove ethylene and thus extend the life of vegetables, fruits and flowers. Ethylene is a gas released by the leaves of growing plants -- but too much of it can build up in an enclosed plant-growth chamber or produce storage facility.

Too much ethylene causes plants to mature too quickly and fruit to ripen prematurely; it even accelerates decay. This hinders researchers' efforts to harvest healthy plants grown in space and would also be undesirable when space travelers build larger space-based greenhouses for growing fresh food.

The research that led to the invention of Bio-KES started with a crucial discovery made in the early 90s by scientists at the Wisconsin Center for Space Automation and Robotics - a NASA Commercial Space Center at the University of Wisconsin- Madison. These scientists collaborated on the discovery with Dr. Marc Anderson, a professor and chemist also at the university.

The research team found that ultra-thin layers of titanium dioxide exposed to ultraviolet light converted ethylene into carbon dioxide and water -- substances that are good for plants. Subsequently, they developed a coating technology that applies titanium-dioxide layers to the surfaces of many materials.

The Wisconsin Center for Space Automation and Robotics used the titanium-dioxide coating technology to design an ethylene scrubber. This first-generation ethylene scrubber was used effectively inside a plant-growth unit, which grew potato plants during a space shuttle mission in 1995. Over the years, scientists refined the ethylene scrubber, and currently the third-generation scrubber is being used successfully inside for plant experiments on the International Space Station.

"Space-based greenhouses may seem to have little to do with the war against terrorism," said Mark Nall, director of the Space Product Development Program at NASA's Marshall Space Flight Center in Huntsville, Ala. "Yet this invention shows how commercial space research can benefit people on Earth in unexpected ways."

KES Science and Technology, Kennesaw, Ga., licensed the TiO2 coating technology from the University of Wisconsin, which allowed them to develop the Bio-KES ethylene scrubber and the Anthrax-killing scrubber for use on Earth. When the ultraviolet light strikes the titanium-dioxide tubes inside the devices, it creates positive and negative electrical charges. These charges tear apart nearby water molecules and produce hydroxyl radicals.

"This hydroxyl by-product disrupts organic molecules and is thus deadly to dust mites, Anthrax and many other pathogens," said John Hayman, president of KES Science and Technology, the company that manufactures the devices. "We put higher-powered ultraviolet lamps in the Anthrax-killing device, so more hydroxyl radicals are produced, giving it an extra kick."