Overexpression of Cu/Zn Superoxide Dismutase (Cu/Zn SOD) in PCC 7942 for Enhanced Azo Dye Removal through Hydrogen Peroxide Accumulation.

Discharge of recalcitrant azo dyes to the environment poses a serious threat to environmental health. However certain microorganisms in nature have developed their survival strategies by degrading these toxic dyes. Cyanobacteria are one such prokaryotic, photosynthetic group of microorganisms that degrade various xenobiotic compounds, due to their capability to produce various reactive oxygen species (ROS), and particularly the hydrogen peroxide (HO) when released in their milieu. The accumulation of HO is the result of the dismutation of superoxide radicals by the enzyme superoxide dismutase (SOD). In this study, we have genetically modified the cyanobacterium   PCC 7942 by integrating Cu/Zn SOD gene () from sp. PCC 9311 to its neutral site through homologous recombination. The overexpression of in the derivative strain was driven using a strong constitutive promoter of the gene. The derivative strain resulted in constitutive production of , which was induced further during dye-treated growth. The genetically engineered   PCC 7942 (MS-) over-accumulated HO during azo dye treatment with a higher dye removal rate than the wild-type strain (WS-). Therefore, enhanced HO accumulation through SODs overexpression in cyanobacteria may serve as a valuable bioremediation tool.