sing metabolic engineering, Cornell Professor David Stern, of the Plant Biology department, has transferred the metabolic pathway of Botryococcus, a species of algae that produces large quantities of usable oil, into another species of algae that has a fast rate of reproduction.
Despite the improvements, there was still not enough oil. “We buy and produce so much oil that to make a dent in the market, one would need to produce massive amounts of biofuel,” Dr. Stern said. “Scaling up is always challenging.”
Rather than abandon this pathway and seeking out a more effective species, Dr. Stern decided to turn to genetic engineering to increase the cell’s net oil production.
In order to find a new, improved variant of the species, scientists must manipulate the algae’s genes. However, as Dr. Stern admits, the scientific community is still unsure of which gene in the algae’s genome is responsible for the effects the team desires. Deducing the combination of genes to alter is a mammoth task. “How many genetic changes would it take to optimize oil production and reproduction in an algal species? Would it be one, 10, 20?”
Instead of focusing on a single mutant strain at a time, Dr. Stern realized that the team would need to create and screen a large number of strains. To do so, the researchers built an entire research facility on a microchip the size of quarter. The chip features hundreds of thousands of individualized compartments, or “bioreactors,” each capable of holding an algal cell. The compartments allowed the team to create different growth environments and experiment with different genetically modified strains of algae.
“As we can create hundreds of thousands of these tiny droplets, we can put single cells in every one of these algal bioreactors and grow them to see how fast they are growing and how much oil they are producing,” he said.
They could then screen millions of cells for improvements in reproductive and oil production rates at the same time. Furthermore, the chip’s plastic construction makes it easy and cheap for other research teams. “One could then use the best variant from screening, and mutagenize and screen it again. This creates the effect of rapid evolution,” Dr. Stern said.
Without the chip, it could take researchers a lifetime to go through only a fraction of these combinations. Instead, scientists can now screen millions of algae mutants at a time with multiple chips, searching for that one “miracle mutant.”