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dc.contributor.authorVijayasankaran, Natarajan
dc.contributor.authorCarlson, Ross P.
dc.contributor.authorSrienc, Friedrich
dc.identifier.citationVijayasankaran N, Carlson R, Srienc F, "Synthesis of poly [(r)-3-hydroxybutyric acid) in the cytoplasm of Pichia pastoris under oxygen limitation," Biomacromolecules, 2005 6(2):604-611en_US
dc.description.abstractWe have constructed a tandem gene expression cassette containing three Ralstonia eutropha poly[(R)-3-hydroxybutyrate] (PHB) synthesis genes under the control of the Pichia pastoris glyceraldehyde-3-phosphate promoter and the green fluorescent protein (Gfp) under the control of the P. pastoris alcohol oxidase promoter. The inducible Gfp reporter protein has been used to rapidly isolate transformed strains with two copies of the entire expression cassette. The isolated strain exhibits Gfp induction kinetics that is twice as fast as that of the strains isolated without cell sorting. In addition, the sorted strains exhibited higher PHB contents in preliminary screening experiments. PHB synthesis was characterized in more detail in the sorted strain and was found to be dependent on culture conditions. It was observed that the specific PHB synthesis rate was dependent on the carbon source utilized and that the conditions of oxygen stress lead to increased fractional PHB content. When this strain is cultivated on glucose under oxygen-limited conditions, the cultures accumulated ethanol during the initial growth phase and then consumed the ethanol for the accumulation of PHB and biomass. While PHB was not synthesized during initial growth on glucose, significant levels of PHB were synthesized when ethanol was subsequently consumed. PHB was also synthesized under aerobic conditions when ethanol was the only carbon source. During growth on ethanol, the specific growth rate of the culture was reduced under oxygen-limited conditions but the specific PHB synthesis rate was relatively unaffected. Thus, the high accumulation of PHB which exceeded 30% of the cell dry weight appears to be the consequence of the decreased biomass growth rate under severe oxygen limitation.en_US
dc.titleSynthesis of poly [(r)-3-hydroxybutyric acid) in the cytoplasm of Pichia pastoris under oxygen limitationen_US
mus.identifier.categoryEngineering & Computer Scienceen_US
mus.relation.collegeCollege of Engineeringen_US
mus.relation.departmentCenter for Biofilm Engineering.en_US
mus.relation.departmentChemical & Biological Engineering.en_US
mus.relation.departmentChemical Engineering.en_US
mus.relation.universityMontana State University - Bozemanen_US
mus.relation.researchgroupCenter for Biofilm Engineering.en_US

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