by Laura Buenning
“Nothing is so powerful as an idea whose time has come” (paraphrased quote, Victor Hugo, 1802 – 1885)
It hasn’t been that long ago that the idea of designing individual biodiesel producing yeast or bacteria cells would have seemed like a pipedream. But today, advanced genetic and microbial engineering tools are changing science-fiction pipedreams to science.
Single cell production, as it is called, intrigues genetic and metabolic engineers Cong Trinh and ORNL’s Adam Guss. The two have joined forces to find out what it would take to turn common yeast, S. cerevisiae, and E. Coli into miniature cell factories that directly convert fermentable sugars, lignin, and the chemical inhibitors found in biomass into an array of advanced biofuels and other biochemicals.
All living organisms select nutritious substances, reject poisonous ones, and organize the sequential chemical reactions required to transform food chemicals into energy. The series of steps required to get from food consumption to growth and reproduction are called metabolic pathways.
Nature creates a network of pathways, Trinh says. So microorganisms can be redesigned to use atypical pathways and, as a result, yield different products. To Trinh and Guss, microbial metabolism offers a playground of opportunity to design microbes capable of producing valuable end products.
Guss’s LDRD team set out to redesign the bacteria E. coil to convert lignin and biomass inhibitors into isobutanol; Trinh’s JDRD team is reengineering the yeast Saccharomyces to change sugars and biomass inhibitors (specifically acetate) into biodiesel instead of ethanol, its usual end product.
In year one Trinh, PhD graduate student Adam Thompston, and postdoc Narayan Niraula mapped out Saccharomyces’ metabolic pathways and then used computer simulation to design the most optimal paths for converting glucose and acetate to biodiesels. This part of the project takes advantage of a huge database of information from industries that use Saccharomyces species to make bread, wine, and beer. Their simulations help determine what laboratory methods to use to create and characterize the required genetic changes—a process they continued into year two of the project.
Their preliminary results detected and quantified biodiesel production in S. cerevisiae and generated isobutanol from E. coli with better physical properties than reported by others in previous research.
“Ultimately we want to create microbial cell factories that will not only make biodiesels, but could also become a platform for other biochemicals derived from biomass,” Trinh says.
Redesigning yeast metabolism for optimal biodiesel production from biomass (year 2)
Cong Trinh, UT Chemical and Biomolecular Engineering Department
Synthetic metabolic pathways for bioconversion of lignin and biomass inhibitors
Adam Guss, ORNL Biosciences Division