These renewable liquids could serve as a more sustainable replacement for today's fossil fuels used to make everyday products like plastic containers and bags, automobile parts, lubricants, and soaps.

The new study by scientists at the University of California, Berkeley, and the University of Minnesota is published online in Nature Chemistry, a leading peer-reviewed chemistry journal by Nature Publishing Group.

It has been difficult for scientists to use plants as a source for plastics because they are mostly made up of sugars, which are nothing like the molecules obtained from petroleum. The key sugar in plants is glucose, which contains too much oxygen and, at six carbons, is too small for many important applications. In order to use plants to make new materials, both problems must be solved -- the conversion process needs to strip oxygen atoms from the glucose, and molecules must be combined to make larger products.

Researchers at the NSF Center for Sustainable Polymers discovered an optimal technology to make sustainable liquids similar to those obtained from petroleum by combining two normally independent technologies. First, glucose obtained from plants was fermented with microbes to remove most of the oxygen. In the second step, metal oxide catalysts stripped the remaining oxygen and combined molecules together to make a useful distribution of olefins, which are the building blocks of the chemical industry.

"Our insight early on was that we needed to find a molecule that could be readily made with fermentation that could strip most oxygen from glucose," said Michelle Chang, a Professor of Chemistry and Chemical and Biomolecular Engineering at the University of California, Berkeley, and leader of the project. "We optimized the chemistry to take advantage of the unique capabilities of molecular biology, after which we could solve the rest of the problem with metal nanoparticle catalysts."

Professor Chang's group developed a unique strain of Escherichia coli that converted glucose to eight- and 10-carbon hydroxy-acids, which are molecules with only a few oxygen atoms at the end of the chain. The microbes were optimized through genetic engineering so that they can 'grow' these molecules from sugar.