BIODEGRADATION OF 2-CHLOROBENZOIC ACID BY RECOMBINANT Burkholderia cepacia UNDER HYPOXIC CONDITIONS IN A MEMBRANE BIOREACTOR

This study examined the feasibility of applying VHb/vgb technology in a membrane bioreactor (MBR) process to treat 2-CBA under hypoxic conditions. The influence of bacterial hemoglobin, VHb, on cometabolic degradation and dechlorination of 2- chlorobenzoate (CBA) by recombinant Burkholderia sp. was investigated at varying concentrations of 2-CBA (0.5–2 mM) and sodium acetate (10–20 mM) under hypoxic conditions in the MBR. The treatment capacity of the MBR system is a function of the amount of biomass retained in the system, increased with corresponding increase in the biomass concentration, and reached a pseudo-steady state with corresponding stabilization in the biomass concentration. MBR enhanced removal of 2-CBA and release of chloride into the culture medium. 2-CBA removal and chloride release rates varied from 99 to 78%, and 98% to 73% depending on the operation conditions, respectively. It has been found that the chloride release is nearly stoichiometric to CBA degradation with over 0.9 molar ratios. COD removal efficiencies were more than 90 % at F: M ratio ranging 0.13–0.20 g/g/day. The observed yield was 0.32–0.62 g biomass/g COD. The stability of plasmid in the recombinant Burkholderia was also monitored during the MBR operation for the application of VHb technology. The stability of the plasmid containing vgb gene in Burkholderia cepacia was 62% even after 156 days without antibiotic pressure. A mathematical for the prediction of biomass concentration in the MBR was developed based on Chang-Alvarez cometabolism model.