Organisms that died many millions of years ago are the source of today’s natural petroleum resources. As phytoplankton and zooplankton, they sank to the bottom of ancient oceans and formed sediments under ground, and were exposed to extreme heat and pressure. This process turned the molecules that built all of their outer and inner membranes, known as fatty acids, into the main hydrocarbon component of petroleum.

However, to become useful for the production of fuels, plastics and detergents, the petroleum-derived hydrocarbons must be chemically ‘cracked’ into shorter chains of medium length with 8 to 12 hydrocarbon molecules and the right set of properties. With increasing length of the hydrocarbon chains, their consistency changes from gas to liquid to wax.

To help avoid further exhausting fossil fuels and the environmental burden posed by refining and cracking petroleum, metabolic engineers are working towards ‘designer fatty acids’ with just the right chain lengths that can be generated in large bacterial cultures, by leveraging the microbes’ own fatty acid synthesis machineries.

“For the production of biofuels and bioplastics, we aim for medium chain lengths that make fatty acids liquid, and give them the desired boiling point, low freezing temperatures and viscosity to be the major components of gasoline and diesel fuels,” said Jeffrey Way, Ph.D., Senior Staff Scientist at the Wyss Institute for Biologically Inspired Engineering. “But thus far we have been missing the right type of enzyme that could efficiently produce medium-length fatty acid chains in bacterial systems.”

“With this study, we fill an important piece into our bigger effort to rewire different stages of fatty acid metabolism of bacteria towards the production of designer molecules for biofuels and bioplastics that could be produced at industrial scale. Being able to do this, in the longer run, could tremendously help save natural resources and sustain our environment,” said Silver, who is also the Elliot T. and Onie H. Adams PrBofessor of Biochemistry and Systems Biology at Harvard Medical School (HMS).


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