Bioremoval of zinc and manganese by bacterial biofilm: A bioreactor-based approach

- Bacterial biofilm-based bioreactor using substrate, Cucumis sativus, showed enhanced uptake of Zn (69.9%) and Mn (78.4%).
- The effective bacterium used in the bioreactor was identified to be the closest neighbour of Pseudomonas beteli.
- SEM-EDX analysis revealed the formation of biofilm on the peels of Cucumis sativus along with uptake of metal ions.
- Adsorption isotherm of the substrate indicated a heterogeneous mode of adsorption which fits Freundlich isotherm kinetics.
- Seed germination assay confirmed detoxification of the synthetic heavy metal solution in treated sorbate.

Industrialization has led to the disposal of a massive amount of heavy metals every year, showing perilous effects on humans, marine life and agricultural products. There are numerous chemical and biological approaches available but their implementation is limited due to high cost and low efficiency. Therefore, the present study was focused on the biofilm- based bioremoval of heavy metals (zinc and manganese) using indigenous bacteria isolated from the tannery sludge obtained from Ranipet, Tamil Nadu. The effective isolate was capable of tolerating up to 2000 mg/L of zinc and manganese and was further used for development of biofilm on the peels of Cucumis sativus. The isolate was found to be a close neighbour of Pseudomonas beteli by 16S rRNA gene sequencing. The uptake efficiency of the biofilm formed on the substrate was estimated to be 69.9% for zinc and 78.4% for manganese by atomic absorption spectroscopy. The scanning electron microscopy showed the biofilm formation on the substrate and also revealed the presence of heavy metal ions adsorbed on the biofilm. The adsorption kinetics of the substrate followed a heterogeneous mode of adsorption of the heavy metals as it showed a higher R2 value for the Freundlich isotherm kinetics as compared to that of Langmuir. Thus, the peels of Cucumis sativus was assessed to be effective for the bioremoval of zinc and manganese.