Researchers at the University of Illinois Urbana-Champaign have discovered a novel method to increase ethanol production from plant sugars through yeast fermentation. The approach, published in Nature Communications, leverages the strengths of two synthetic yeast strains and precise timing to achieve higher ethanol yields than previous methods.

The scientists created an artificial microbial community comprising a glucose-specializing yeast strain and a xylose-specializing strain. By carefully controlling the timing of introducing these strains to the sugar mixture, they significantly enhanced ethanol production.

"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."

Glucose and xylose are the most abundant sugars derived from plant biomass breakdown. While the commonly used yeast strain Saccharomyces cerevisiae prefers glucose and struggles with xylose, the researchers found that a division of labor approach with specialist yeast strains could overcome this efficiency bottleneck.

The team conducted experiments varying the order and timing of yeast strain introduction, as well as the population ratios. They also developed a mathematical model, trained with experimental data, to predict optimal fermentation conditions and validate the results.

"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 study found that adding the xylose-fermenting strain first, followed by the glucose strain 14 to 29 hours later, more than doubled ethanol production. This demonstrates the potential of engineered microbial communities for biofuels production and other bioprocessing applications.

"This study demonstrates the functional potential of division of labor in bioprocessing and provides insight into the rational design of engineered ecosystems for various applications," the authors wrote.

The research was supported by the Department of Energy and the Korea Research Institute of Bioscience and Biotechnology.