The cost and environmental impact of producing liquid biofuels and biochemicals as alternatives to petroleum-based products could be significantly reduced, thanks to a new metabolic engineering technique discovered by a group of researchers at MIT. A distinguished Greek professor at MIT’s department of Chemical Engineering, Gregory Stephanopoulos is among the contributing researches that brought about this new technique. The fuels and chemicals are often produced using microbes to convert sugars from corn, sugar cane, or cellulosic plant mass into products such as ethanol and other chemicals, by fermentation. However, this process can be expensive, and developers have struggled to cost-effectively ramp up production of advanced biofuels to large-scale manufacturing levels. One particular problem facing producers is the contamination of fermentation vessels with other, unwanted microbes. These invaders can outcompete the producer microbes for nutrients, reducing yield and productivity. In a paper published in the journal Science, researchers at MIT and the Cambridge startup Novogy describe a new technique that gives producer microbes the upper hand against unwanted invaders, eliminating the need for expensive and potentially harmful sterilization methods. The researchers engineered microbes, such as Escherichia coli, with the ability to extract nitrogen and phosphorous — two vital nutrients needed for growth — from unconventional sources that could be added to the fermentation vessels, according to Gregory Stephanopoulos, the Willard Henry Dow Professor of Chemical Engineering and Biotechnology at MIT, and Joe Shaw, senior director of research and development at Novogy, who led the research. “We created microbes that can utilize some xenobiotic compounds that contain nitrogen, such as melamine,” Stephanopoulos says. Melamine is a xenobiotic, or artificial, chemical that contains 67 percent nitrogen by weight.