Cloning and Expression of Poly 3-Hydroxybutyrate Operon Into Escherichia coli

Poly 3-Hydroxybutyrate (PHB), a class of Poly Hydroxyalkanoates (PHAs), is a group of bacterial storage polymers, produced by various microorganisms in response to nutrient limitation. PHAs are biodegradable polymers which could be a good substitute for current petrochemical plastics. PHB has been synthesized during three enzymatic steps including three genes.

Our aim was PHB production from recombinant bacteria.

Ralstonia eutropha was cultured and its genomic DNA was extracted. The phbCAB operon was amplified using designed primers. The fragment was cloned into pET-28a expression vector and then transformed into Escherichia coli BL21. Sudan black staining was used to show the production of PHB.

The extracted recombinant plasmid was digested with restriction enzymes. Separation of the desired fragment from the vector was performed to prove the correct insertion of the PCR products into the vector. The colony PCR and sequencing results confirmed the successful transformation. The production of PHB was confirmed by Sudan Black B staining under a light microscope.

Various metabolic and fermentation methods have been used in some bacterial strains for PHB production. The use of a recombinant system harboring PHB synthesis genes can produce PHB in higher concentrations compare to natural PHA-producing bacteria. The present study was one of the most important and basic steps of designing a recombinant E. coli that can produce PHB.