Microbial Division of Labor Produces Higher Biofuel Yields

Feb 06, 2024

By Diana Yates

Scientists have found a way to boost ethanol production via yeast fermentation, a standard method for converting plant sugars into biofuels. Their approach, detailed in the journal Nature Communications, relies on careful timing and a tight division of labor among synthetic yeast strains to yield more ethanol per unit of plant sugars than previous approaches have achieved.

"We constructed an artificial microbial community consisting of two engineered yeast strains: a glucose specialist and a xylose specialist," said Yong-Su Jin, a professor of food science and human nutrition at the University of Illinois Urbana-Champaign, who co-led the new research with U. of I. bioengineering professor Ting Lu. "We investigated how the timing of mixing the two yeast populations and the ratios in which the two populations were mixed affected the production of cellulosic ethanol."

Postdoctoral researcher Jonghyeok Shin and Siqi Lao, a Ph.D. student in the Center for Biophysics and Quantitative Biology at the U. of I., carried out the work.

Glucose and xylose are the two most abundant sugars obtained from the breakdown of plant biomass such as agricultural wastes. The team was trying to overcome a common problem that occurs when using yeast to convert these plant sugars into ethanol. In the wild, the yeast strain of interest, Saccharomyces cerevisiae, prefers glucose and lacks the ability to metabolize xylose. Other scientists have used genetic engineering to alter the yeast so that it also consumes xylose, but these engineered strains still prefer glucose, reducing their overall efficiency in ethanol production.

Some scientists have pursued the idea that communities of microbes, each with its own special function, can operate more efficiently than a single, highly engineered strain.

"My group is dedicated to the design, analysis and engineering of synthetic microbial communities. Jin's lab specializes in yeast metabolic engineering and biofuel production," Lu said.

"Our complementary expertise enabled us to test whether a division-of-labor approach among yeast might work well in biofuels production."

The researchers conducted a series of experiments testing the use of their two specialist yeast strains. They altered the order in which the different strains were added to the sugar mixture and the timing of each addition.

"We also investigated the ratios at which the two populations were mixed to determine their effects on the rapid and efficient production of cellulosic ethanol," Jin said.

The team also developed a mathematical model that accurately predicts their yeasts' performance and ethanol yields.

"We used the data from the experiments to train our mathematical model so that it captures the characteristic ecosystem behaviors," Lu said. "The model was then used to predict optimal fermentation conditions, which were later validated by corresponding experiments."

The researchers discovered that adding the xylose-fermenting yeast specialist to the mixture first, followed 14 to 29 hours later by the glucose specialist, dramatically boosted ethanol production, more than doubling the yield.

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Video: Why Your Food Future Could be Trapped in a Seed Morgue

In a world of PowerPoint overload, Rex Bernardo stands out. No bullet points. No charts. No jargon. Just stories and photographs. At this year’s National Association for Plant Breeding conference on the Big Island of Hawaii, he stood before a room of peers — all experts in the science of seeds — and did something radical: he showed them images. He told them stories. And he asked them to remember not what they saw, but how they felt.

Bernardo, recipient of the 2025 Lifetime Achievement Award, has spent his career searching for the genetic treasures tucked inside what plant breeders call exotic germplasm — ancient, often wild genetic lines that hold secrets to resilience, taste, and traits we've forgotten to value.

But Bernardo didn’t always think this way.

“I worked in private industry for nearly a decade,” he recalls. “I remember one breeder saying, ‘We’re making new hybrids, but they’re basically the same genetics.’ That stuck with me. Where is the new diversity going to come from?”

For Bernardo, part of the answer lies in the world’s gene banks — vast vaults of seed samples collected from every corner of the globe. Yet, he says, many of these vaults have quietly become “seed morgues.” “Something goes in, but it never comes out,” he explains. “We need to start treating these collections like living investments, not museums of dead potential.”

That potential — and the barriers to unlocking it — are deeply personal for Bernardo. He’s wrestled with international policies that prevent access to valuable lines (like North Korean corn) and with the slow, painstaking science of transferring useful traits from wild relatives into elite lines that farmers can actually grow. Sometimes it works. Sometimes it doesn’t. But he’s convinced that success starts not in the lab, but in the way we communicate.

“The fact sheet model isn’t cutting it anymore,” he says. “We hand out a paper about a new variety and think that’s enough. But stories? Plants you can see and touch? That’s what stays with people.”

Bernardo practices what he preaches. At the University of Minnesota, he helped launch a student-led breeding program that’s working to adapt leafy African vegetables for the Twin Cities’ African diaspora. The goal? Culturally relevant crops that mature in Minnesota’s shorter growing season — and can be regrown year after year.

“That’s real impact,” he says. “Helping people grow food that’s meaningful to them, not just what's commercially viable.”

He’s also brewed plant breeding into something more relatable — literally. Coffee and beer have become unexpected tools in his mission to make science accessible. His undergraduate course on coffee, for instance, connects the dots between genetics, geography, and culture. “Everyone drinks coffee,” he says. “It’s a conversation starter. It’s a gateway into plant science.”