Breakthroughs in Plant Based PHB Production

Crops have the potential to not only be a source of food and fuel but also a source of renewable materials. One of the most interesting classes of materials are the polyhydroxyalkanoate (PHA) family of microbial carbon and energy storage polymers. PHAs are targeted as replacements for petroleum derived plastics but can also be used for water treatment and enhanced feeds. Oilseeds are an ideal production platform for PHAs since seed metabolism is well suited to the polymer biosynthetic pathways and multiple co-products can be harvested (polymer, oil, meal) increasing the value of the seed.

Yield10 and its predecessor company, Metabolix, have a long history of using synthetic biology to develop advanced PHA production organisms including microbes and plants. This capability includes developing novel biosynthetic pathways to multiple co-polymers from cellular metabolites enabling the production of PHAs with a wide range of properties in bacteria. Recently Yield10 has made significant progress producing polyhydroxybutyrate (PHB), the simplest member of the PHA family, in the oilseed Camelina sativa. We previously demonstrated production of high levels of PHB in Camelina seeds by targeting enzymes for PHB synthesis to the seed plastids, however seedlings were severely impaired in emergence and survival. Yield10 has demonstrated a cytosolic PHB production pathway with an ER targeted polymerizing enzyme PHA synthase that produced PHB levels up to 10.2% of the seed weight with good seedling survival. These lines have been tested in small scale field trials and seed from the best lines is currently being scaled up in the field. These results are a significant step forward towards commercial production of PHB in plants, enabling a direct link between low cost large scale agricultural production of this exciting biodegradable plastic and the packaging and foodservice segment of the 350 million ton per year global plastics market.