Bioaugmentation of the decolorization rate of acid red GR by genetically engineered microorganism Escherichia coli JM109 (pGEX-AZR)

Abstract

The study showed that the genetically engineered microorganism (GEM) bioaugment successfully the dye wastewater biotreatment systems to enhance acid red GR (ARGR) removal. Escherichia coli JM109 (pGEX-AZR) was the GEM with higher azoreductase activity. The kinetics of the ARGR decolorization by the E. coli JM109 (pGEX-AZR) agreed with Andrews model. The kinetic parameters, rdye,max, Ks and Ki, were found to be 42.45 mg g−1 h−1, 584.93 mg L−1 and 556.89 mg L−1, respectively. The E. coli JM109 (pGEX-AZR) was tested in anaerobic sequencing batch reactors (AnSBR) in order to enhance the ARGR decolorization. The decolorization rate of ARGR was affected by the amount of E. coli JM109 (pGEX-AZR) inoculation and the best amount of inoculation was 10%. The continuous operations of the four bioreactors with different E. coli JM109 (pGEX-AZR) immobilization supports showed that the E. coli JM109 (pGEX-AZR) could bioaugment decolorization in AnSBRs with suspended and immobilized on macroporous foam carriers. For 42 days continuous operation in the AnSBRs, both the tolerance to ARGR concentration shock and the decolorization rate in these two bioaugmented AnSBRs are higher than those of the other two systems, control system and bioaugmented AnSBRs system with the sodium-alginate immobilized cells, the decolorization rate reached 90%. Changes in microbial community were detected by ribosomal intergenic spacer analysis (RISA) and amplified ribosomal DNA restriction analysis (ARDRA), which revealed that the introduced E. coli JM109 (pGEX-AZR) was persistent in the augmented systems and maintained higher metabolic activity.