Tuesday, April 30, 2013
Exhibit Hall
The conversion of polyhydroxyalkanoates (PHA) to alkenes is a potential route that is being examined to efficiently convert biomass-derived intermediates into fuel products that are compatible with the existing fuel distribution infrastructure. This route appears promising as there are several microorganisms that incorporate high levels of PHA (up to 80% DCW) as a form of energy storage molecule to be metabolized when other energy sources are not available. Thermal breakdown of PHA proceeds via an intermediate carboxylic acid, which can then be decarboxylated to an alkene. Oligomerization of alkenes by well known commercial technologies would permit production of a range of hydrocarbon fuels from sugar intermediates. Polyhydroxybutyrate (PHB) can be produced in Cupriavidus necator on a variety of carbon sources including glucose, fructose and glycerol with PHB accumulation reaching 75% DCW. We have demonstrated the thermal breakdown of PHB to 2-butenoic acid (crotonic acid, CA) and the thermal decarboxylation of CA to propene at yields approaching 70% at 400 oC in 15 min. Combining the breakdown and decarboxylation steps we have demonstrated that PHB can be directly converted to propene and carbon dioxide under similar conditions and in similar yields. PHB containing cell mass from C. necator has also been directly converted to propene and carbon dioxide without prior separation of PHB from the cell mass. Current research is aimed at finding catalysts that would permit lower temperature decarboxylation and higher propene yields.