Biopolymers: Long polyester synthesized by E. coli

Ultrahigh-molecular-weight polyhydroxybutyrate (UHMW-PHB, Mw>3,000,000) synthesized by genetically engineered Escherichia coli is an environmentally friendly bioplastic material which can be processed into strong films or fibers.

 However, the efficient production of UHMW-PHB is proving to be technologically challenging.

 Here, Takeharu Tsuge and colleagues at Tokyo Institute of Technology, Keio University, and State University of New York have shown that rearrangement of gene order in the PHB biosynthesis operon (phaCAB) is an effective method for producing UHMW-PHB in E. coli.

 The three genes of the phaCAB operon are phaC, which encodes PHB synthase, phaA and phaB, which encode monomer-supplying enzymes. The researchers examined the effect of gene order of the phaCAB operon (phaABC, phaACB, phaBAC, phaBCA, phaCAB, and phaCBA) in order to determine the best organization for the production of UHMW-PHB.

 Experimental results showed that the molecular weights and production levels of PHB were both dependent on the order of the relatives of the pha genes to the promoter. The most balanced production result was achieved using the phaBCA order.

 This finding is an important contribution for the construction a highly efficient UHMW-PHB system for producing for this commercially important polymer.


Reference:
 

• Authors: Ayaka Hiroe, Kenji Tsuge, Christopher T. Nomura, Mitsuhiro Itaya, and Takeharu Tsuge.
• Title of original paper: Rearrangement of gene order in the phaCAB operon leads to effective production of ultrahigh-molecular-weight poly[(R)-3-hydroxybutyrate] in genetically engineered Escherichia coli.
• Journal, volume, pages and year: Applied and Environmental Microbiology 78, 3177 (2012).
• Digital Object Identifier (DOI): 10.1128/AEM.07715-11
• Affiliations: Department of Innovative and Engineered Materials, Tokyo Institute of Technology; Institute for Advanced Biosciences, Keio University; and Department of Chemistry, State University of New York College of Environmental Science and Forestry.
• Department website:http://www.iem.titech.ac.jp/tsuge/english.html