title: Microbubble assisted polyhydroxybutyrate production in Escherichia coli.
abstract: BACKGROUND
  One of the potential limitations of large scale aerobic Escherichia coli fermentation is the need for increased dissolved oxygen for culture growth and bioproduct generation. As culture density increases the poor solubility of oxygen in water becomes one of the limiting factors for cell growth and product formation. A potential solution is to use a microbubble dispersion (MBD) generating device to reduce the diameter and increase the surface area of sparged bubbles in the fermentor. In this study, a recombinant E. coli strain was used to produce polyhydroxybutyrate (PHB) under conventional and MBD aerobic fermentation conditions.
  
  
  RESULTS
  In conventional fermentation operating at 350 rpm and 0.8 vvm air flow rate, an OD600 of 6.21 and PHB yield of 23 % (dry cell basis) was achieved. MBD fermentation with similar bioreactor operating parameters produced an OD600 of 8.17 and PHB yield of 43 % PHB, which was nearly double that of the conventional fermentation.
  
  
  CONCLUSIONS
  This study demonstrated that using a MBD generator can increase oxygen mass transfer into the aqueous phase, increasing E. coli growth and bioproduct generation.
authors.affiliation: Department of Molecular Biology and Genetics, Karadeniz Technical University, Trabzon, Turkey.
authors.forename: Kadriye
authors.initials: K
authors.lastname: Inan
authors.affiliation: Department of Biology, Karadeniz Technical University, Trabzon, Turkey.
authors.forename: Fulya Ay
authors.initials: FA
authors.lastname: Sal
authors.affiliation: Bioengineering Branch, Space Biosciences Division, NASA Ames Research Center, Moffett Field, Ames, CA, 94035-1000, USA.|Universities Space Research Association, Mountain View, CA, 94043, USA.
authors.forename: Asif
authors.initials: A
authors.lastname: Rahman
authors.affiliation: Department of Biological Engineering, Utah State University, 4105 Old Main Hill, Logan, UT, 84322-4105, USA.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Putman
authors.affiliation: Department of Biological Engineering, Utah State University, 4105 Old Main Hill, Logan, UT, 84322-4105, USA.
authors.forename: Foster A
authors.initials: FA
authors.lastname: Agblevor
authors.affiliation: Department of Biological Engineering, Utah State University, 4105 Old Main Hill, Logan, UT, 84322-4105, USA. charles.miller@usu.edu.
authors.forename: Charles D
authors.initials: CD
authors.lastname: Miller
mesh_terms: D058491:Bacterial Load; D019149:Bioreactors; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D005285:Fermentation / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D045423:Microbubbles; D010100:Oxygen / Q000737:chemistry / Q000494:pharmacology*; D011091:Polyesters / Q000378:metabolism*; D012995:Solubility
chemical_list: D011091:Polyesters; C107955:poly(4-hydroxybutanoate); D010100:Oxygen
keywords: Dissolved oxygen; Fermentation; Microbubble; PHB; Polyhydroxybutyrate