Isolation Of Chlorobenzene-Degrading Strain And Its Application In Bioaugmenting Chlorobenzene-Treating BTF

Chlorobenzenes (CBs) are widely used in industrial process, and their chemical properties are very stable. Because of their bioaccumulation, toxicity and carcinogenicity, they were listed as priority pollutants by EPA. To control the emission of such pollutants, biodegradation technology has several advantages such as high-efficiency, low-energy consumption, ambient reaction coditions, and low secondary pollution.A high-effective strain was obtained in this work. This isolated was assigned to be Ralstonia pickettii, was named as L2, which was possibly to be a new species able to degrade CB compounds. The characteristics, kinecitic models, metabolites, and the activity of the related enzymes were investigated, and the possible degradative pathway was proposed based on the above results.The optimal conditions for the growth of L2 were at 30℃and pH 7.0. Yeast extract (YE) could remarkably enhance the growth of L2 and chlorobenzene degradation. The Haldane modification of the Monod equation adequately described the relationship between the specific growth rate and substrate concentrations. The maximum specific growth rate and specific degradation rate were 0.23 h^-1 and 0.18 h^-1, respectively. The yield coefficient was 0.25 mg of biomass produced/mg of CB consumed, respectively. This isolate could finally mineralize the CB into non-toxic carbon dioxide, water, chloride ion, etc. The identities of main metabolic intermediates were confirmed by GC/MS analysis IC and HPLC. The pathways for CB degradation were proposed by identification of metabolites and assay of ring cleavage enzymes in cell extracts.Based on the degradative performance and metabolic characteristic, strain L2 was employed to bioaugment bio-trickling filter (BTF) degrading CB. Three sets BTF reactors were inoculated with L2,―L2 + acclimated sludge‖and acclimated sludge, respectively. The biofilm was successfully formed after the BTFs were operated for 30 days, indicating the successful start-up. The start-up period of the BTF inoculated by L2 and―L2 + acclimated sludge‖was shorter, indicating that L2 can enhance the start-up of the BTF degrading CB. The CB in the BTFs followed Michaelis-Menten kinetic model, the rmax (specific maximum degration rate per volum) were 76.3, 83.6 and 35.6 g/m3·h, respectively, which further suggested the bioaugmentation of L2 in the BTF.The BTF inoculated with―L2 + acclimated sludge‖exhibited good removal performance and the relatively high CO₂ production compared to the other two BTFs, indicating L2 could bioaugment the CB biodegradation in the BTF, which has obvious advantages and application value in practice.According to the results of real-time PCR quantitatification and sequences and homology matching species of the bands by PCR-DGGE, Ralstonia pickettii L2 could stably existed in the BTFs since it was introduced into the reactor. This indicated thatL2 still grows well under the conditions of the presence of other strains, efficiently degraded chlorobenzene, and could strengthen chlorobenzene degradation in the BTF, suggesting a promising industrial application. According to PCR-DGGE fingerprinting analysis, the microbial species were very rich and had the relative stability and complexity of microbial community structure in three BTFs. Meanwhile, it was proposed that the relative stability and complexity possibly promote the CB biodegradaton in three BTFs.