Previous studies successfully transformed PHB synthetic operon (phaCAB) into Escherichia coli and PHB could be produced by the recombinant strain. In order to increase the fraction of 3-hydroxyvalerate (3HV) in PHBV, we cloned the propionate permease gene prpP (prpPcn) from C. necator H16 and the propionyl-CoA synthase gene preE (prpEct)from Cupriavidus taiwanensis 184 and transformed into an E. coli host harboring pBHB2 (pBluescript SK- derivative, containing C. necator H16 phaCAB operon and vgb gene). The effects on the accumulation of PHAs in cells co-expression of pBHB2 and prpEcn or prpEct grown in different compositions of media were evaluated. Results showed when cultivated in the media contained mixed carbon sources (i.e. glucose and sodium propionate), the bacteria were all able to synthesize PHBV with the HV fraction in PHBV were 8.4% (pBHB2 only), 9.8% (pBHB2:prpPcn) and 16.1% (pBHB2:prpEct), respectively. When glucose was replaced to sodium pyruvate, sodium succinate or sodium gluconate, only PHB were detected in all three recombinant strains. In addition, the concentrations of yeast extracts could also affect the fraction of HV in the polymers produced.
11-25: Effects of different substrate composition on biosynthesis of polyhydroxybutyrate-co-hydroxyvalerate (PHBV) by recombinant Escherichia coli
Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
Polyhydroxyalkanoates (PHAs) are biocompatible and biodegradable polyesters accumulated by various bacteria. They are useful for the development of non-petroleum based biodegradable plastics. Cupriavidus necator (formally known as Ralstonia eutropha) is well known for its ability to accumulate PHB. When supplemented with propionic acid (or sodium propionate) in the growth medium, the bacterium is able to synthesize polyhydroxybutyrate-co-hydroxyvalerate (PHBV) with less than 5% HV fraction.