Urgun-Demirtas Meltem, Pagilla Krishna R, Stark Benjamin C
Department of Chemical and Environmental Engineering, Illinois Institute of Technology, 10 West 33rd Street, Chicago, IL 60616, USA.
Biotechnol Bioeng. 2004 Jul 5;87(1):110-8. doi: 10.1002/bit.20102.
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).
在连续培养恒化器中研究了透明颤菌血红蛋白（VHb）技术在缺氧条件下对洋葱伯克霍尔德菌DNT菌株降解2 - 氯苯甲酸（2 - CBA）的应用。在不同稀释率下研究了重组菌（含VHb基因（vgb））和未转化细胞的脱氯能力，以确保2 - CBA完全降解。随着稀释率从0.025 h⁻¹增加到0.25 h⁻¹，重组菌和未转化细胞的氯释放量与降解的2 - CBA浓度之比分别从0.95降至0.72和从0.89降至0.39。未转化细胞中氯释放与2 - CBA降解之间的非化学计量关系更为明显。在一系列稀释率下，重组菌细胞密度比未转化细胞密度高0.1 - 0.2 g L⁻¹。随着稀释率增加，两种菌株的氧摄取率（OUR）和底物利用率（SUR）均降低。两种菌株的OUR/SUR比均随稀释率增加而升高，但重组菌株的该比值比未转化细胞高得多。重组菌细胞的特定2 - CBA降解率高于未转化细胞（分别为1.17和0.46 mg CBA（mg）⁻¹天⁻¹），重组菌细胞的半饱和常数低于未转化细胞（分别为0.18和0.32 mg CBA L⁻¹）。重组菌细胞的假一级降解常数k(1CBA)和k(1ACE)高于未转化细胞（分别为6.5 L（mg细胞）⁻¹天⁻¹和95.6 L（mg细胞）⁻¹天⁻¹）（分别为1.44 L（mg细胞）⁻¹天⁻¹和73.7 L（mg细胞）⁻¹天⁻¹）。
