Microorganism production of bioplastic from non-food plant resources

Kaneka Corporation (based in Osaka; President: Mamoru Kadokura), in a joint research project with Keiji Numata, team leader of the Enzyme Research Team, Biomass Engineering Program Cooperation Division, Center for Sustainable Resource Science (based in Yokohama, Kanagawa; Director: Kazuo Shinozaki), RIKEN (based in Wako, Saitama; President: Ryoji Noyori), and team, has successfully biosynthesized polyhydroxyalkanoic acid (PHA), a type of bioplastic, generated by microorganisms using degradation products of lignin, a plentiful component found in wood, as a carbon source.

As the world starts to move away from petroleum resources, the focus of research is shifting to the possibilities of production from plant resource. Much progress has been made in the degradation of plant resource such as cellulose to produce sugar. However lignin, while freely available in wood, has attracted less interest due to low degradability and the issue of some degradation products being harmful to microorganisms.

Kaneka, together with team leader Keiji Numata and team, tried to synthesize PHA through biosynthesis by many microorganisms with a sole carbon source of aromatic compounds that make up lignin or similar aromatic compounds. It was found that the bacteria Ralstonia eutropha H16 (Cupriavidus necator), known to be a producing strain for PHA, biosynthesized PHA from the lignin component 4-Hydroxybenzoic acid (4-HBA) and numerous other aromatic compounds. 4-HBA achieves good productivity, with PHA accumulation within the microorganism reaching around 63 wt% of dry cell weight. Although the molecular weight of the biosynthesized PHA is slightly lower than that of PHA produced from sugar or vegetable oil, it showed properties that make it suitable for use in plastic products such as film.

The success opens the way for the development of basic technology that aims for microorganism material production using lignin, applications of which were difficult to date. Also, this technology can be applied for the utilization of waste effluents including lignin degradation products from paper mills, etc., and by combining it with the wide variety of bio-refinery technologies, it is expected to spawn a new biomass industry.