That's the conclusion from researchers at the University of California, Berkeley, who report 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. Such a sensor-regulator system could eventually make advanced biofuels cheaper and bring them a step closer to being an economically viable replacement to petroleum-based products.

One issue that has limited the amount of biofuels that a microbe makes is an imbalance of the different biological ingredients, or precursors, used to make the final fuel product. In a study published this week in Nature Biotechnology, Jay Keasling, professor of chemical engineering and bioengineering at UC Berkeley, and colleagues describe 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.