2‐Chlorobenzoate Biodegradation by Recombinant Burkholderia cepacia under Hypoxic Conditions in a Membrane Bioreactor

Abstract

The feasibility of applying bacterial hemoglobin technology to degrade 2‐chlorobenzoate (2‐CBA) through co‐metabolism under hypoxic conditions in a membrane bioreactor (MBR) process has been studied in the laboratory. 2‐chlorobenzoate removal and chloride release rates in the MBR system varied from 99 to 78% and 98 to 73%, respectively, depending on the operation conditions. Chemical oxygen demand (COD) removal efficiencies were more than 90% at food‐to‐microorganism ratios ranging from 0.32 to 0.62 g/g/d, and the observed yield was 0.13 to 0.20 g biomass/g COD. The bacterial cell‐floc size‐distribution analysis showed that there is a significant change in bacterial floc size due to high shear stress during operation of the MBR. To characterize growth kinetics of Burkholderia cepacia strain dinitrotoluene, a mathematical model that describes co‐metabolic oxidation of 2‐CBA in an MBR has been developed.

Improvement of bioremediation by Pseudomonas and Burkholderia by mutants of the Vitreoscilla hemoglobin gene (vgb) integrated into their chromosomes

“…One of these applications is transformation of vgb into bioremediating bacteria, in which the presence of vgb/VHb sometimes results in enhancement in growth and metabolism of aromatic compounds; benzoic acid, 2-chlorobenzoic acid, and 2,4-dinitrotoluene have been tested [3,7,14,17,19,26,27]. In most of these studies vgb has been introduced on a plasmid, but we have also been able to stably integrate vgb into the host chromosome using the transposon-conjugation-based system developed by Timmis and coworkers [4,9], in order to produce more genetically stable strains that may be more useful in practical applications.…”

Microbial transformation of chlorinated benzoates

“…The bacterium, Burkholderia cepacia was genetically engineered by inserting bacterial hemoglobin genes to perform better at low dissolved oxygen. The engineered strain (DNT) was shown to effectively cometabolize 2-CBc at low dissolved oxygen levels in a membrane bioreactor (Urgun-Demirtas et al 2005). Table 2 summarizes the performance of several anaerobic bioreactor studies towards the removal of different chlorinated benzoate congeners.…”