Smarter Biofuel Bugs

RESULTS: Synthetic biologists in California demonstrated a way to triple the amount of biodiesel a type of bacteria can make from sugar. They equipped the bacteria with a protein that senses the level of certain biological chemicals in a cell and changes gene activity in response. This creates a feedback loop that continually optimizes fuel production.

WHY IT MATTERS: Biofuels have trouble competing with fossil fuels in part because organisms are inefficient factories: they make too much of one ingredient or another. The researchers reduced that waste. This new approach could ultimately make biofuels less expensive.

METHODS: The researchers started with a strain of designer E. coli that creates biodiesel from two biological building blocks: fatty acids and ethanol. They engineered the bacteria to produce a naturally occurring protein that can sense the amount of fatty acids in a cell and regulate the activity of various genes in response. The researchers modified the bacterial genome to specify which genes the protein would control—directing it, for example, to slow production of ethanol when fatty-acid levels are low and to speed it up when they are high.

NEXT STEPS: Yields need to improve further for commercial production; even at triple what they were, they’re still at only 28 percent of the theoretical maximum. The researchers will now try to introduce similar gene-regulating mechanisms that can improve other parts of the process or be used to make a variety of chemicals in addition to biodiesel.