Enhanced polyhydroxybutyrate (PHB) production via the coexpressed phaCAB and vgb genes controlled by arabinose PBAD promoter in Escherichia coli

Aim:  To develop an approach to enhance polyhydroxybutyrate (PHB) production via the coexpressed phaCAB and vgb genes controlled by arabinose PBAD promoter in Escherichia coli. Method and Results:  The polyhydroxyalkanoates (PHAs) synthesis operon, (phaCAB), from Ralstonia eutropha was overexpressed under the regulation of the arabinose PBAD promoter in Escherichia coli, and the vgb gene encoding bacterial haemoglobin from Vitreoscilla stercoraria (VHb) was further cloned at downstream of phaCAB to form an artificial operon. The cell dry weight (CDW), PHB content and PHB concentration were enhanced around 1·23-, 1·57-, and 1·93-fold in the engineered cell harbouring phaCAB–vgb (SY-2) upon 1% arabinose induction compared with noninduction (0% arabinose). Furthermore, by using a recombinant strain harbouring PBAD promoter-vgb along with native promoter-phaCAB construction, the effect of vgb expression level on PHB biosynthesis was positive correlation. Conclusions:  The results exploit the possibility to improve the PHB production by fusing the genes phaCAB–vgb from different species under the arabinose regulation system in E. coli. It also demonstrates that increase in VHb level enhances the PHB production. Significance and Impact of the Study:  We were successful in providing a new coexpressed system for PHB synthesis in E. coli. This coexpressed system could be regulated by arabinose inducer, and is more stable and cheaper than other induced systems (e.g. IPTG). Furthermore, it could be applied in many biotechnology or fermentation processes.