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Enhanced kinetics of genetically engineered Burkholderia cepacia : the role of vgb in the hypoxic metabolism of 2‐CBA
Author(s) -
UrgunDemirtas Meltem,
Pagilla Krishna R.,
Stark Benjamin C.
Publication year - 2004
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.20102
Subject(s) - recombinant dna , dilution , kinetics , microbiology and biotechnology , burkholderia , strain (injury) , biology , cell culture , hemolysis , biochemistry , chemistry , bacteria , gene , immunology , physics , genetics , anatomy , quantum mechanics , thermodynamics
Application of Vitreoscilla hemoglobin (VHb) technology to 2‐CBA degradation by Burkholderia cepacia strain DNT under hypoxic conditions was studied in continuous culture chemostats. Dechlorination abilities of both recombinant (VHb gene ( vgb ) containing) and untransformed cells were investigated at various dilution rates to ensure complete degradation of 2‐CBA. As the dilution rate increased from 0.025 to 0.25 h −1 , the ratios of chloride release to degraded 2‐CBA concentration decreased from 0.95 to 0.72 and from 0.89 to 0.39 for recombinant and untransformed cells, respectively. A nonstoichiometric relationship between chloride release and 2‐CBA degradation was more pronounced for untransformed cells. Recombinant cell densities were 0.1‐0.2. g L −1 greater than untransformed cell densities for a range of dilution rates. As the dilution rate increased, the oxygen uptake rate (OUR) and the substrate utilization rate (SUR) decreased for both strains. The OUR/SUR ratio increased as the dilution rate increased for both strains but was much higher for the recombinant strain compared to untransformed cells. The specific 2‐CBA degradation rate of recombinant cells was greater than that of untransformed cells (1.17 vs. 0.46 mg CBA (mg) day −1 , and half‐saturation constants for recombinant cells were lower than those of untransformed cells (0.18 and 0.32 mg CBA L −1 , respectively). The pseudo‐first‐order degradation constants, k 1CBA and k 1ACE , were higher for recombinant cells (6.5 L (mg cells) −1 day −1 and 95.6 L (mg cells) −1 day −1 , respectively) than those of untransformed cells (1.44 L (mg cells) −1 day −1 and 73.7 L (mg cells) −1 day −1 , respectively). © 2004 Wiley Periodicals, Inc.