MOFFETT FIELD, Calif. – For long-duration space missions, astronauts someday will grow plants for food and the air they breathe, while transforming inedible parts of the plants into useful resources, such as biofuels, food, and chemicals.
Today, scientists at NASA Ames Research Center, Moffett Field, Calif., are working on a method to transform the wasted parts of plants into food and fuel, using what is called bionanotechnology. The research team is assembling enzyme structures with multiple functions, modeled after a natural enzyme complex that breaks down inedible plant material into usable sugars.
“Turning waste into resources is our purpose,” said Chad Paavola, a research scientist at Ames. “We’re working on a process that converts cellulose into sugar. Cellulose is a common substance found in all plants, including wheat straw, corn stalks, and woody material. Its sugar can be converted into other resources, such as food, fuels or chemicals.” Paavola is a contributing author of the paper entitled “The Rosettazyme: A Synthetic Cellulosome” published in the July 30 issue of the Journal of Biotechnology.
Cellulose is an attractive raw material for producing sugar because of its abundance. However, it is difficult to access the sugar in cellulose, because it is arranged in structures called polymers that are difficult to break down. In nature, enzyme complexes, known as cellulosomes, are among the most effective ways to convert cellulose into useable sugars.
To better understand how cellulosomes work and to mimic their function, the team of NASA scientists built enzyme complexes modeled after natural cellulosomes, using protein parts from different microbes.
By placing the microbes DNA sequences, or genetic blueprints, for these component parts into a common laboratory bacterium, the scientists were able to create a protein structure to act as a scaffold to attach enzymes with different functions, allowing the enzymes to work together more efficiently. In this arrangement, the enzymes produce significantly more sugar from cellulose than the same enzymes produce when they are not attached to the scaffold.
The NASA scientists reached a milestone demonstrating the feasibility of duplicating nature by building multi-enzyme arrays on a self-assembling scaffold of their own design.
“This is an exciting result,” said Jonathan Trent, an astrobiologist at NASA Ames and contributing author of the paper, who initiated the project. “We succeeded in assembling a complex nano-scale structure with diverse components that self-assembles and serves a useful purpose. Its like a Swiss army knife of enzymes. This brings us a small step closer to functional nano-engineering.”
For further information about the research, please see: Shigenobu Mitsuzawu, Hiromi Kagawa, Yifen Li, Suzanne L. Chan, Chad D. Paavola and Jonathan D. Trent. "The Rosettazyme: A Synthetic Cellulosome," Journal of Biotechnology, July 30, 2009.