According to new research published in the journal Science this week, microbiologists at Chalmers University of Technology have developed a new type of thermotolerant yeast that will enable ethanol and other biofuels to be produced much more efficiently. They have proven that one simple mutation enables yeast growth at significantly higher temperatures.
Details on the thermotolerant yeast research
Lead researcher Jens Nielsen, a professor of systems biology at Chalmers, noted that one basic mutation was all that was needed for yeast to become thermotolerant. Nielson continued to explain that normal yeast cells have ergosterol in their cell membranes. The mutation that provides for a thermotolerant strain of yeast substitutes fecosterol – a more “bent” molecule — for this ergosterol.
New thermotolerant yeast is a “natural mutation”
Instead of using one of the direct gene modification techniques often used today, the researchers decoded to use time-tested adaptive laboratory evolution. So they just cultivated a number of batches of yeast at 40 degrees Celsius over a three-month period. After 300 generations, more yeast began to survive and within a few more generations the cultivations were thriving.
It turned out all batches of the new thermotolerant yeast had mutations in the ERG3 gene that replaced ergosterol with fecosterol. The fecosterol increased cell membrane stability, allowing the yeast to survive at higher temperatures. Moreover, the study also established that the thermotolerant trait was passed on to future generations.
Yeast thermotolerance means dramatic increases in biofuel production efficiency
Yeast is used to convert corn and other crops into ethanol or related biofuels. With the current types of yeast, the vats must be cooled to ensure the individual yeast cells are not killed by the heat they produce themselves. Yeast is typically cooled to around 30 degrees Celsius during ethanol production, but the process could be more efficient and less expensive if yeast cultivation could be undertaken at 40 degrees Celsius. The new yeast would remove the cost of continuously maintaining the yeast at 30 degrees Celsius. In the ethanol production process, the yeast break down starch in grains like corn into individual sugar molecules. This reaction works best at 40 degrees Celsius.