Mathematical modeling of the consortium composed of the xylose and glucose specialists. Credit: Jonghyeok Shin et al.
University of Illinois researchers have developed a novel method to increase ethanol production via yeast fermentation. Relying on a division of labor approach, the method developed produces more ethanol per unit of plant sugar than is currently possible with today's methodology.
The method, published in Nature Communications, relies on careful timing and a division of labor amongst synthetic strains of yeast.
“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, “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 two of the most abundant sugars resulting from the breakdown of plant biomass. A common challenge of converting these sugars to ethanol is the natural preference of Saccharomyces cerevisiae, the yeast strain used, towards glucose and its inability to metabolize xylose. Current methods often rely on genetically altering the yeast to consume xylose, but even after genetic modification the strains still prefer glucose reducing their ethanol production efficiency.
To overcome this challenge the team developed a method that relies on two specialized strains to break down both glucose and xylose. To optimize the method the team altered the order in which the strains were added, as well as the timing of each addition.
“We used the data from the experiments to train our mathematical model so that it captures the characteristic ecosystem behaviors,” said Ting Lu, a bioengineering professor at the University of Illinois. “The model was then used to predict optimal fermentation conditions, which were later validated by corresponding experiments.”
The resulting method drastically boosted ethanol production to nearly two times what is possible with current methodologies. “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 added.