Blog: Super yeasts and catalysts

By Susanne Retka Schill | October 24, 2016

Biofuels research continues to unveil tantalizing possibilities. Two reports this past week from the University of Wisconsin and ORNL caught my eye.  

University of Wisconsin researchers have developed a super yeast, a strain of saccharomyces that will eat both glucose and xylose. The story of how they achieved that is intriguing. As one who writes about science and technology, I particularly appreciated the analogy used by the unidentified writer in the UW news release. “[They] gave the yeast a choice akin to eating carrots for dinner or nothing at all, surrounding S. cerevisiae with xylose until it re-evaluated its distaste for xylose or died.”   After 10 months and hundreds of generations, of “directed evolution,” a strain was found that converted xylose. The researchers identified the specific gene mutations, and then were able to successfully reverse engineer the parent strain to consume xylose as well.  Read more about the University’s news release here.

The researchers hope their discovery sparks similar work by others:  “[Researcher Trey ] Sato says this work could enable a wide variety of biofuels research going forward. With the technique for making Y128 published, researchers are free to make it themselves for the purposes of applying it to new biomass pretreatment technologies or to different plant materials. ‘Scientists won’t need to adapt their research to the process that we’re doing here,’ he says. ‘They can just take our technology and make their own strain.’”

I checked with Trey, who said the Wisconsin Alumni Research Foundation has filed a provisional patent application identifying the mutations and their effects on xylose fermentation. “However, any academic research lab can certainly take the information in the publication and apply it to their own strain,” he said. Companies interested in using the technology in a strain for commercial purposes will need to license the intellectual property.

The techniques will no doubt add to the scientific knowledge that has led to the recently introduced yeast strains with altered metabolic pathways. There’s work to be done with the Wisconsin yeast strain, of course. Trey says that some of the mutations that help with xylose metabolism negatively affect the yeast’s ability to cope with stress, reducing yields. “We need to better understand how these mutations help with xylose fermentation, so that we can find alternative genetic changes that will maintain both xylose fermentation and stress tolerance.”

The second research study reported this past week shows progress on another front. Researchers at Oak Ridge National Laboratory reported the discovery of an electrochemical process that uses tiny spikes of carbon and copper to turn carbon dioxide into ethanol. What’s intriguing is that the catalyst is made from relatively common materials, rather than expensive or rare metals, utilizing advances in nanotechnology.  

The discovery was an accident of sorts. Starting out as a study of the first step in a proposed reaction, the researchers realized the catalyst was doing the entire reaction. Using the nanotechnology catalyst in a solution of carbon dioxide dissolved in water and applying electric current, they got ethanol. “Ethanol was a surprise—it’s extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst,” said the lead author of the ORNL paper, Adam Rondinone.

“Given the technique’s reliance on low-cost materials and an ability to operate at room temperature in water, the researchers believe the approach could be scaled up for industrially relevant applications. For instance, the process could be used to store excess electricity generated from variable power sources such as wind and solar,” the article says.

It would be an intriguing new use for ethanol, if it were to become the storage medium for wind and solar power. Imagine the implications of storing surplus power as ethanol, and the need for efficient generators to turn it back into electricity for peak loads. It could create a whole new market for ethanol.

The story doesn’t suggest it, but every one in the ethanol industry knows there would also be the potential to collocate the system to utilize the carbon dioxide produced in fermentation. It will take time to fully test the technology and scale it up, and there may be many unseen hurdles to overcome.

Many such research discoveries die on the vine. The skeptics will say, sure, you’ve been talking about cellulosic ethanol being commercial within the next five years for the past 20 years. But I’m thinking down the road it will seem as though it was with lightning speed.  Consider how we look back on electricity and incandescent lighting as discoveries that happened quickly. But, we all know the story of Benjamin Franklin’s kite. Electricity was known in the mid-1700s. Then I looked up Thomas Edison’s light bulb. He wasn’t the first to invent the light bulb, the national park service site I found said, but he was the first to make one that was practical and would burn for hours—13 hours was considered a revolutionary improvement. The year? 1879. The Edison Electric Illuminating Company of New York was formed in 1882, bringing electric light to parts of Manhattan, but it was 50 years before electric lights gained respectable market share. Only in 1925 did half of all homes in the U.S. have electric power.

Biofuels advancements are past the Ben Franklin stage for sure, and somewhere in the Edison spectrum. I don’t think anyone can predict how long it will be before they become as old hat as the incandescent bulb. And just look how long it’s taken before incandescent is finally being replaced with something more efficient – but not without a little bit of help with policies forcing the issue.