Reduction of [Co(iii)–EDTA]−complex by a novel process using phototrophic granules: a step towards sustainable bioremediation

This study shows that phototrophic granules are more efficient as compared to microbial granules or monoculture bacterial culture and are a self-sustainable system to be used in bioremediation process of environmental contaminants.

A spectrophotometric method for the determination Co-EDTA complexes

A precise quantification of Co(II)EDTA complex is required to develop bioremediation approaches for Co(III)EDTA complex that is generated in various industrial processes. It is cumbersome to quantify Co(II)EDTA in a mixture of Co(II)EDTAand Co(III)EDTAby normal UV-visible spectrophotometric methods as both the complexes absorb significantly at 490 nm, which is the λ max of Co(II)EDTA. Whereas other sophisticated techniques such as gas chromatography, atomic absorption spectrophotometer, inductively coupled plasma-atomic emission spectroscopy can measure individual species of Co(II)EDTA or Co(III)EDTA when present alone but are ineffective to measure the Co(II)EDTAprecisely when it is mixed with Co(III)EDTA. Hence, an attempt has been made to develop a spectrophotometric method for its quantification. This paper describes the development of a simple and economic dual wavelength spectrophotometric method for the determination of Co(II)EDTAin a mixture of Co(II)EDTA and Co(III)EDTA complexes. The wavelength pair, 490-580 nm was optimized for the measurement of absorbance for this dual wavelength method of determination of Co(II)EDTA in the presence of Co(III)EDTA. Int J Appl Sci Biotechnol, Vol 3(4): 584-587

Microbial reduction of [Co(III)-EDTA]⁻ by Bacillus licheniformis SPB-2 strain isolated from a solar salt pan

Naturally stressed habitats are known to be repositories for novel microorganisms with potential bioremediation applications. In this study, we isolated a [Co(III)-EDTA](-) reducing bacterium Bacillus licheniformis SPB-2 from a solar salt pan that is exposed to constant cycles of hydration and desiccation in nature. [Co(III)-EDTA](-) generated during nuclear waste management process is difficult to remove from the waste due to its high stability and solubility. It is reduced form i.e. [Co(II)-EDTA](2-) is less stable though it is toxic. This study showed that B. licheniformis SPB-2 reduced 1mM [Co(III)-EDTA](-) in 14 days when grown in a batch mode. However, subsequent cycles showed an increase in the reduction activity, which was observed up to four cycles. Interestingly, the present study also showed that [Co(III)-EDTA](-) acted as an inducer for B. licheniformis SPB-2 spore germination. Vegetative cells germinated from the spores were found to be involved in [Co(III)-EDTA](-) reduction. More detailed investigations showed that after [Co(III)-EDTA](-) reduction, i.e. [Co(II)-EDTA](2-) complex was removed by B. licheniformis SPB-2 from the bulk liquid by adsorption phenomenon. The bacterium showed a D10 value (radiation dose required to kill 90% cells) of ∼250 Gray (Gy), which signifies the potential use of B. licheniformis SPB-2 for bioremediation of moderately active nuclear waste.

Removal of toxic Co-EDTA complex by a halophilic solar-salt-pan isolate Pseudomonas aeruginosa SPB-1

In this study, a promising bioremediation approach was developed to remove [Co(III)-EDTA](-) complex that is generated during the waste management process. Though several studies have been reported on bioremediation of cobalt, the removal of [Co(III)-EDTA](-) complex has not been tested. A [Co(III)-EDTA](-) resistant bacterium, Pseudomonas aeruginosa SPB-1 was isolated from the solar-salt-pan and physical parameters were optimized for its growth. The various studies showed that the removal of [Co(III)-EDTA](-) from the bulk liquid was due to the adsorption of the complex by the biomass. Using absorption/desorption isotherm over a range of pH (1-8), the maximum adsorption of [Co(III)-EDTA](-) was found to be at pH 7.0 and maximum desorption from the biomass occurred at pH 1.0, thus rendering an ion exchange property to P. aeruginosa SPB-1 biomass. P. aeruginosa SPB-1 biomass could be used as bio-resin that showed 80.4±3.27% adsorption capacity up to fourth cycle and the biomass was viable till the ninth cycle with 10.5±7.3% adsorption. Radiation tolerance potential i.e. D10 value for the strain was found to be ~300 Gy, which suggests the potential use of the bacterium in bioremediation of moderately active nuclear waste.