Threefold increase in cyanobacteria bioplastic production

February 17, 2014

Discovery of new gene Rre37 and elucidation of a metabolism control system

A RIKEN CSRS researcher group has achieved a threefold increase in production of PHB (polyhydroxybutyrate, a type of bioplastic), by modifying cyanobacterial genes.

The group previously found that a protein, named Rre37 which is a response regulator induced by nitrogen depletion, controls carbon metabolism of cyanobacteria. Researchers generated genetically engineered cyanobacterial strain, which overexpressing rre37 in unicellular cyanobacterium Synechocystis sp. PCC 6803. The rre37-overexpressing strain produced PHBs under nitrogen starvation at twice levels of the control strain. In addition, double overexpression of rre37 and sigE, which encodes another regulator of PHB biosynthesis, enhanced the amount of PHB by three times.

In this study, transcriptome and metabolome analyses were performed using the rre37-overexpressing strain. Combining these data, we propose a new metabolic cycle, which is a hybrid of the TCA and ornithine cycle. In this way, we have preceded both basic and applied science of photosynthetic organisms.

These results contribute to novel way of bioproduction of PHB from carbon dioxide derived via microalga. Further understanding of molecular mechanisms of PHB production in cyanobacteria will lead to the enhancement of bioplastic production in the future.


Original article
Plant Physiology doi: 10.1104/pp.113.232025
T. Osanai, A. Oikawa, K. Numata, A. Kuwahara, H. Iijima, Y. Doi, K. Saito, M. Yokota Hirai,
"Pathway-Level Acceleration of Glycogen Catabolism by Response Regulator Rre37 in the Cyanobacterium Synechocystis sp. PCC 6803".

Masami Hirai: Team Leader
Takashi Osanai: Visiting Scientist
Metabolic Systems Research Team, Metabolomics Research Group