title: Functional cis-expression of phaCAB genes for poly(3-hydroxybutyrate) production by Escherichia coli.
abstract: OBJECTIVE
  To develop a microbial strain producing poly(3-hydroxybutyrate) [P(3HB)], in the absence of antibiotic supplementation (normally required to stabilize a recombinant plasmid), by constructing a recombinant Escherichia coli strain with phaCAB and vgb integrated into the chromosome.
  
  
  RESULTS
  The polyhydroxyalkanoate (PHA) synthesis operon (phaCAB) and the bacterial haemoglobin gene (vgb) were integrated downstream of nlpB (novel lipoprotein B) in E. coli K12, via homologous recombination, to form a recombinant strain, termed YH100. VHb encoded by the vgb gene was successfully expressed in YH100, as confirmed by Western blotting. P(3HB) synthesis by the YH100 strain grown in the absence of antibiotic was analysed by transmission electron microscopy. The yield of P(3HB) is 208 mg g(-1) . The thermal stability of P(3HB) produced from YH100 was similar to that of commercial P(3HB). Further, the polydispersity index (PDI) of the P(3HB) polymer derived from YH100 was 1·37, indicating that polymer uniformity was greater than that of commercial P(3HB), which had a PDI of 1·47.
  
  
  CONCLUSIONS
  We successfully constructed a recombinant E. coli strain expressing exogenous genes, specifically phaCAB from Cupriavidus necator and vgb from Vitreoscilla stercoraria, integrated into the downstream of chromosomal dapA-nlpB locus. P(3HB) was stably produced by this strain, without any need for antibiotic supplementation to stabilize a recombinant plasmid at least for 48h.
  
  
  CONCLUSIONS
  We report a genetic locus, the downstream of the nlpB locus in E. coli, in which the transcription of the exogenous genes is driven by the dapA-nlpB promoter without the need for the addition of inducer and antibiotic.
authors.affiliation: Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, 701 Section 3 Zhongyang Road, Hualien, Taiwan, R.O.C.  
authors.forename: Y-T
authors.initials: YT
authors.lastname: Horng
authors.forename: C-C
authors.initials: CC
authors.lastname: Chien
authors.forename: Y-H
authors.initials: YH
authors.lastname: Wei
authors.forename: S-Y
authors.initials: SY
authors.lastname: Chen
authors.forename: J C-W
authors.initials: JC
authors.lastname: Lan
authors.forename: Y-M
authors.initials: YM
authors.lastname: Sun
authors.forename: P-C
authors.initials: PC
authors.lastname: Soo
mesh_terms: D020118:Cupriavidus necator / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000235:genetics; D006885:Hydroxybutyrates / Q000737:chemistry / Q000378:metabolism*; D009876:Operon / Q000235:genetics; D010641:Phenotype; D010957:Plasmids; D011091:Polyesters / Q000737:chemistry / Q000378:metabolism*; D054813:Polyhydroxyalkanoates / Q000235:genetics* / Q000378:metabolism*; D011995:Recombination, Genetic; D020589:Vitreoscilla / Q000235:genetics; D000094122:Polyhydroxybutyrates
chemical_list: D029968:Escherichia coli Proteins; D006885:Hydroxybutyrates; D011091:Polyesters; D054813:Polyhydroxyalkanoates; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates