Abstract

An estimated 1.8 trillion pounds of plastics are produced every year, mostly from non-renewable resources. Population growth and economic expansion has resulted in increasing demand for plastics worldwide. However, pollution from plastic industry, both solid waste and greenhouse gas are problems that must be managed. Through technological advances in genetic and metabolic engineering, we are creating innovative solutions for producing bio-renewable plastics and fossil fuel replacements from plant biomass. Today, high biomass C-4 grasses, such as sugarcane, have been successfully engineered for the production of bioplastics and other industrially important chemicals. Especially promising are Polyhydroxybutyrate (PHB), a short chain length polyhydroxyalkanoate (PHA). PHA’s have properties similar to a range of petrochemical derived plastics. Moreover, we have now engineered sugarcane to produce PHB in the leaves at levels approaching commercial relevance. To complete a successful transition from research to commercialization of plant derived PHAs, an economical extraction and purification technology has to be developed. Although commercial scale extraction methods for microbial produced PHAs are well advanced, plant based extraction is only now being researched. As lignocellulosic based biorefineries start commercial production of biobased fuels and chemicals, new opportunities arise for accessing our biopolymers locked in the cells of sugarcane leaves. The key technologies involve acid hydrolysis, steam explosion, enzyme degradation, pyrolysis, or various combinations of these for dismantling cellulose and hemicellulose to sugars and removal of the lignin. We routinely acid hydrolyze plant tissue from our engineered sugarcane by overnight boiling in concentrated sulfuric acid, which not only breaks down the plant tissue buts also breaks PHB down to crotonic acid. While crotonic acid is a valuable industrial chemical in its own right, a new method is needed for an efficient extraction of the PHB polymer, as well capturing the fermentable sugars, and lignin. Here we discuss a strategy to break down plant biomass to extract the fermentable sugars, lignin, and PHA with little or no degradation of the PHA.