Jay Keasling (left) and Fuzhong Zhang at Berkeley’s Joint BioEnergy Institute. (Roy Kaltschmidt, Berkeley Lab)
University of California, Berkeley researchers have developed a genetic sensor that enables bacteria to adjust their gene expression in response to varying levels of key intermediates for making biodiesel. As a result, the microbes produced three times as much fuel. The sensor-regulator system could eventually make advanced biofuels cheaper.

One issue that has limited the amount of biofuels that a microbe makes is an imbalance of the different precursors used to make the final fuel product. Jay Keasling, professor of chemical engineering and bioengineering at UC Berkeley, and colleagues developed a biological sensor system that lets bacteria regulate genes in its biofuel-production pathways according to the amount of certain precursors in the cell.

The researchers augmented a previously reported strain of engineered E. coli that creates biodiesel from two biological building blocks—fatty acids and ethanol. Over the life cycle of that strain, one precursor can be produced at a higher level than another - an inefficient and sometimes harmful situation.

Keasling and coworkers designed a microbe, using a naturally occurring sensor, that responds to the amounts of internal fatty acids and related molecules and tunes the activity of its pathways accordingly. When limited amounts of fatty acid are in the cell, the sensor-regulator molecules puts the brakes on both the ethanol-producing pathway and the fatty acid-converting pathway. Conversely, when the bacteria contain higher levels of fatty acids, the brakes on these pathways are released.

(Technology Review)