Biodegradation of 2-Chlorobenzoate by Recombinant Burkholderia Cepacia Expressing Vitreoscilla Hemoglobin Under Variable Levels of Oxygen Availability

Publisher Website
Google Scholar
Abstract
The influence of bacterial hemoglobin, VHb, on dechlorinationand degradation of 2-chlorobenzoate (2-CBA) by recombinantBurkholderia sp. under variable oxygen availability with an initial dissolved oxygenconcentration of 0.27 mM-0.72 mM was investigated in batch and continuous culture. Abilityto express VHb was provided to recombinant Burkholderia by transformationwith the VHb gene, vgb, on plasmid pSC160. 100% of 0.5 mM CBA was degraded incultures with 85% and 70% of total volume as headspace air in closed reactorsby both wild type and recombinant Burkholderia. The recombinant cultures were able todechlorinate and degrade 100% of the 2-CBA in less than 48 hours at 30 °Ccompared to more than 120 hours for wild type cultures. The rate and extent of CBAdegradation by recombinant cultures with 40% of total volume as headspace air was higher than thoseachieved by wild type cells at the end of the 168 hours of incubation period, 98and 73%, respectively. The chloride released: CBA degraded molar ratio for cultures with 40%of total volume headspace air was nearly stoichiometric (molar ratio = 1.0) for recombinantstrains, whereas it was non-stoichiometric (molar ratio = 0.24)for wild type cells. The results suggest a suicidal meta-pathway for wild type cells and a complete dechlorinationand degradation pathway for recombinant cells under hypoxic conditions.The degradation and dechlorination ability of both types of cells was alsoinvestigated in continuous reactor studies by varying the dilution rate under hypoxicconditions. Regarding potential of the recombinant strain for 2-CBA degradation in eitheropen ecosystems or closed bioreactor bioremediation systems, the stability of the plasmidcontaining vgb in the recombinant cells was also studied; the plasmid was100% stable at 0.025 h-1 dilution rate (∼1.7 d hydraulic retention time),even after one month.

This publication has 0 references indexed in Scilit: