Microbe engineered to produce new product at lower temperatures

By Erin Voegele | April 23, 2012

A team of researchers at the University of Georgia’s Department of Biochemistry and Molecular Biology recently published the results of a study relating to hyperthermophiles—or heat-loving microorganisms—that may prove beneficial to biofuel production. The paper, titled “Engineering a Hyperthermophilic Archaeon for Temperature-Dependent Production Formation,” was published in the scientific journal mBio, the online open-access journal of the American Society for Microbiology, on April 17.

According to information released by ASM, the researchers have found a way to control a hyperthermophile with a temperature switch. As a result, the microorganism can manufacture product at low rather than high temperatures. The ASM notes that the development could lead to easier manufacturing of biofuels. In the study, the authors note that this work represents the first time a targeted modification of a hyperthermophile has been accomplished.

The team’s work focused on the hyperthermophile Pyrococcus furiosus. The archaeon is a single-celled organism that resembles bacteria, but can carry out many processes that bacteria cannot. It was originally isolated from a hot marine environment. P. furiosus grows best at temperatures near 212 degrees Fahrenheit. According to the report, its enzymes are stable at high temperatures, making it a commonly used tool in the biotechnology sector.

To complete its research, the team inserted a lactate dehydrogenase gene from another organism into P. furiosus. The organism from which the gene was taken prefers to grow at relatively low temperatures. As a result, the protein product of the lactate dehydrogenase gene is most stable at these lower temperatures. Information released by ASM specifies that the research team inserted the new gene adjacent to a cold shock promoter that essentially turns on the genes around it when P. furiosus is in temperatures of approximately 141 degrees Fahrenheit. As a result, when the microorganism is in the relatively cold 141 degree Fahrenheit temperature, lactate production is turned on. When it is heated to 212 degrees Fahrenheit, lactate production is turned off. The authors note that this helps prevent the need for chemical inducers.

“The hyperthermophile is essentially the bioreactor that contains the foreign enzymes,” said Michael Adams, lead author of the paper. “P. furiosus just supplies cofactors and a cytoplasmic environment for the highly active foreign enzymes,” he said. This makes for a cleaner, more controllable reaction.

Another benefit of the technology developed by Adams and his team is that since lactate production is essentially turned off at lower temperatures, the new gene doesn’t interfere with the microorganism’s original metabolism. Similarly, the production of lactate wouldn’t be impacted by P. furiosus’ original metabolism, as the other materials it produces would be essentially turned off at lower temperatures.

In the paper, the authors note that when the new strain was grown at 208 degrees Fahrenheit, sugar was fermented to produce acetate and hydrogen, but lactate was not detected. Alternatively, when the strain was grown at 161 degrees, lactate was produced.

According to the report, the research was supported by the Bioenergy Science Center, Oak Ridge National Laboratory, and by the ARPA-E Electrofuels Program. A full copy of the research paper can be accessed on the mBio website.