NREL's Min Zhang Keeps Her "Bugs" Happy, Leading to Biofuel Breakthroughs

National Renewable Energy Laboratory Senior Scientist Min Zhang has a special relationship with Zymomonas mobilis, a rod-shaped bacterium that has bioethanol-producing capabilities. Of her 80 peer-reviewed papers and 21 U.S. patents in the field of biochemistry and biofuels, many reference this sugar-eating "bug."

Their fortuitous pairing began shortly after the Chinese-born U.S. citizen and biochemical engineer arrived at NREL in 1992. She came as part of a newly created team tasked by what was then the Energy Department's National Bioethanol Program with exploring a new path for ethanol conversion for biofuels. At the time, global researchers were focusing on using yeast for alcohol production.

"That [yeast] organism was the one people had studied for years. We at NREL decided to take a different approach," Zhang said. They chose instead the fermentative bacteria known to scientists as Zymomonas mobilis.

"We felt it could be very promising," she said, explaining that the organism could consume glucose very fast—three times faster than yeast—as well as produce ethanol at high yield, which would potentially improve fuel production cost. By tapping that hunger, researchers could use the bacterium to speed up the process of turning the sugars (such as those derived from the long-chain cellulose and hemicellulose found in feedstock) into useable fuels and products.

Next, the four-member NREL team successfully engineered the bug for pentose metabolism—pentoses are 5-carbon sugars that have been shown to be less appealing to organisms than 6-carbon sugars such as glucose. Zhang and the team had more positive results. "We ended up with a breakthrough," she said, and their work garnered national attention. In 1995, Science magazine published "Metabolic Engineering of a Pentose Metabolism Pathway in Ethanologenic Zymomonas mobilis," and the editors of R&D Magazine named the process a prestigious R&D 100 Award winner.

Three cooperative research and development agreements (CRADAs) followed, including a major commitment with DuPont. The NREL/DuPont CRADA covered the entire span of biofuel technology, from biomass to ethanol. Scientists and engineers from DuPont and NREL worked collaboratively for years to further improve the biomass-to-ethanol conversion process, including the biocatalyst development using Zymomonas. Following some additional improvements, DuPont is now in the process of using the technology at their new cellulosic ethanol plant in Nevada, Iowa, where they plan to produce 30 million gallons of biofuels per year from the non-food parts of plants.

"I'm pleased to see that kind of dream come true, and proud that the technology could end up in a commercial place," said Zhang, who traveled to the site for the October 30 grand opening of the $225 million plant.

In honor of her many contributions, this year Zhang was given the Battelle Memorial Institute Inventor of the Year award as well as the Distinguished Innovator Award at NREL's Innovation and Technology Transfer Awards. At the tech transfer event, the Energy Department's Assistant Secretary for Energy Efficiency and Renewable Energy David Danielson presented her with the award, and she in turn thanked "my dear colleagues, the team that has a lot of talent and has put a lot of effort into this work."

Source: National Renewable Energy Laboratory (NREL)
Date: Dec 9, 2015