Sugars into polymers

To dramatically improve the efficiency of microbial fermentation, Cambridge, MA-based Metabolix plans a two-year project to reengineer the central metabolism of Escherichia coli (E. coli) to convert renewable sugars into a family of high-performance polymers at greatly increased yields.

Most of today's plastics and synthetic polymers are produced from petrochemicals. Bio-based products represent an attractive alternative to conventional plastics, which persist in the environment and are a significant source of environmental pollution.

But although bacteria produce chemicals that could be commercially useful, such microbial routes are inefficient by industrial standards and tend to produce unwanted byproducts.

The two-year project is intended to reduce the cost of producing polyhydroxyalkanoates (PHAs), a family of biodegradable polyesters with attractive properties that could replace many petroleum-based plastics used today. In a typical fermentation, the microbe is fed a sugar and another substance, called a co-feed, which controls the final polymer composition.

Metabolix has engineered bacteria that efficiently convert the co-feed, and now seeks to develop a method to convert sugar to the main constituent of industrially useful PHAs.

The company will re-engineer the primary metabolic process - a feat never achieved before - by enhancing the activity of the desired biochemical pathway and eliminating or greatly reducing two competing pathways. All these traits then will be combined into a single strain of a new microbe.

The company will track changes in the activity of specific genes to increase understanding of the metabolic engineering process. Funding from the NIST (National Institute of Science and Technology) Advanced Technology Program (ATP) is expected to accelerate development of the new technology by at least three years.

The engineered microbes will provide a platform for cost-effective, environmentally benign production of a range of plastics and resins from renewable raw materials.

The PHAs, which are superior to competing biodegradable polymers, would provide new solutions for packaging, personal hygiene products, matrices for controlled release treatments for oil wells, and other applications such as hydrophobic coatings for water-resistant cartons.

In addition, the new metabolic engineering method could be applied to fermentation processes for making a wide variety of other chemical compounds.